Flooring Tips.
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OSB Over Board Subflooring As Carpet Substrate?. . . . . . . . . . . . . . . . . . . . . . . 3
Materials Play Critical Role In Dance-Floor Design. . . . . . . . . . . . . . . . . . . . . . . . 3
Are Bamboo Building Products Really Green?. . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Reducing The Carbon Footprint Of Your Flooring . . . . . . . . . . . . . . . . . . . . . . . . . 5
Heavily Loaded Drywall Carts Damage Wood Panels And Floor Systems. . . . . . . . 7
Snow On Your Truflor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Uneven Floors? Check What’s Happening Below. . . . . . . . . . . . . . . . . . . . . . . . . 9
Measuring Moisture In Osb Sub-Floor Panels. . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Raised Wood Flooring Systems Reduce Flood Damage . . . . . . . . . . . . . . . . . . . 10
Removing A Piece Of OSB Subflooring. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Installation Tips For Tongue And Groove Structural Panels. . . . . . . . . . . . . . . . . 12
Expansion Joints In Flooring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Tiling Tips: Prevent Bathroom Tiles From Tenting . . . . . . . . . . . . . . . . . . . . . . . 14
Creating the perfect crawlspace . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Installing Ceramic Tiling Over OSB Subflooring. . . . . . . . . . . . . . . . . . . . . . . . . 16
Installing OSB Wood Panels Over Concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Drilling Drainage Holes Into Truflor Subflooring. . . . . . . . . . . . . . . . . . . . . . . . . 18
Installing Hardwood Flooring Over OSB Panels . . . . . . . . . . . . . . . . . . . . . . . . . 19
Types Of Subfloors You Can Use Under Hardwood Flooring . . . . . . . . . . . . . . . . 20
How To Fill The Chips In Your Subfloor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
I-Joist Installation Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Can I Glue Vinyl Planks Directly To My Subfloor?. . . . . . . . . . . . . . . . . . . . . . . . 23
Underlayment Installation Tips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Melting Ice On Osb Sub-Floor Paneling With Calcium. . . . . . . . . . . . . . . . . . . . . 25
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Flooring Tips
OSB Over Board Subflooring As Carpet Substrate?
Question
In a renovation of an old home can I use 7/16-inch OSB sub-flooring panels over
1-inch rough pine boards for carpet underlayment?
Answer
Yes, you can use OSB, as long as you leave a 1/8” space between panels to
allow for adjustments to changing moisture conditions. Ensure that the diagonal
board subflooring screwed down to prevent squeaks. Sand any uneven joints or
areas and then apply a PL400 sub-floor adhesive to the OSB and screw it to the
subflooring. Install the carpet and enjoy!
Materials Play Critical Role In Dance-Floor
Design
David Sukonick is one of the leading designers
and builders of wooden floors for performers
with over 300 professional dance floors under
his belt. David has undertaken many unique
designs and specializes in the sprung sub
floor. Says David of his unusual choice in
construction design: “It is definitely an unusual
field and to my knowledge I may be the only
person that specializes solely in the design and
installation of custom dance floors.”
David Sukonick comes to the profession with
a unique perspective. With over 30 years’
experience as a professional dancer, he has an unparalleled insight into the injuries that can be sustained
when floors are poorly constructed as well as an insider’s viewpoint on what dancers need in the perfect
floor.
David has, over the decades that he has been building dance floors, perfected his technique. He has
tried and tested materials until he has found those which offer the ultimate combination of strength and
flexibility. “Professional dance floors must contain a much greater amount of spring than a gymnasium
or other hardwood floor. The surface is extremely important, as it must serve a multitude of functions. It
must contain a fairly specific amount of slip resistance. It must be flexible and at the same time have the
durability and density to withstand tap dancing or have a piano rolled over it without damage.”
David and his team build a variety of dance floors to fit the studio and budget. His floors range from 2 ¾”
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in height to 5 ¾” and go from four to six distinct levels of spring with insulation to provide sound proofing.
The team and usually complete a floor of around 2,000 sq. ft. in three days.
Finding the right material has always been one of the greatest challenges. The hardwood still varies
according to the requirements, tastes and budgets of the clients, but the underlying structures have been
perfected over time and trial. “I always use a reliable base because any imperfections here will show in
the floor of course. I have found the Norbord OSB TruFlor subflooring to be incredibly resilient. I can have a
couple of my guys jumping up and down on these and they just don’t break,” said David.
Watch a time-lapse recording of one of his recent construction sites:
http://www.youtube.com/watch?v=XvFugjF7cB8
Are Bamboo Building Products Really Green?
As building codes focus on environmentally-friendly
materials and clients become more demanding,
many builders are turning to greener products. The
wood industry is one of the leading renewables and
has had many decades to perfect its sustainability
with certifications and controlled plantations. Many
newer products on the market, like bamboo, make
lofty promises of sustainability but can actually be
quite harmful to the environment.
A recent study by Dovetail Partners revealed that
the Chinese bamboo industry portrays itself as
sustainable and green, but in reality poses several
concerning environmental issues: “Problems reported throughout bamboo-producing regions included
clearing of natural forests for establishment of bamboo plantations; creation of monoculture plantations;
loss of biodiversity; substantial use of fertilizers and pesticides despite claims that bamboo crops
required neither of these treatments; and unsustainable harvesting of natural stands of bamboo.”
Bamboo has a long history in construction and today, more than one billion people live in homes
constructed of this resilient species of grass. Bamboo was introduced as a flooring option in the late
1990’s, but met with an icy reception despite its beauty and the fact that it is as strong as hardwood.
This changed in 2002 when the USGBC included bamboo flooring as a renewable, environmentally-friendly
materials in its Leadership in Energy and Environmental Design (LEED) 2.1 standard.
Within three years, Chinese production of bamboo flooring had increased significantly and non-certified
bamboo became a widely accepted green alternative.
Effects Of Bamboo Farming On The Environment
The effects of the bamboo industry on the environment have been devastating in many parts of China.
Here are some of the salient points from the Dovetail study.
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•Biodiversity has been affected as only one kind of bamboo (moso bamboo) is being farmed. Many
of the natural bamboo forests have been overharvested and many varieties of bamboo and other
plants have been removed leaving only moso bamboo.
•Bamboo farming has been successful in improving the economies of some provinces and this has
led to widespread razing of natural forests to make way for bamboo.
•Artificial pesticides and fertilizers are used on bamboo crops to increase yields. These chemical
additives leach into ground water, rivers and streams. Maoyi and Xiaosheng (2004): “As a fastgrowing plant, bamboo consumes substantial quantities of nutrients. It is estimated that, on
average, farmers annually apply 200kg (440 pounds) of fertilizer (mainly nitrogen) per hectare to
bamboo plantations.”
•Bamboo grows in tropical conditions and needs to be irrigated regularly which consumes valuable
water resources.
While the new LEED standard requires bamboo to be farmed in plantations that comply with the
Sustainable Agriculture Standard, the majority of bamboo products remain uncertified. FSC-certified
products are available, but the cost of certification means few farmers pursue this route. This certification
has also come under fire for approving bamboo grown on large monoculture plots. The blanket green
status awarded to all bamboo construction materials should be revisited and third-party certification must
be instituted before this can be considered a truly sustainable material.
The Dovetail study concludes: “…bamboo products should never be designated as environmentally
preferable materials without at the very least requiring careful consideration of environmental impacts
throughout the entire supply chain. It is time for all players in the green building arena to replace rapid
renewability credits with a bit of common sense.”
Reducing The Carbon Footprint Of Your Flooring
When comparing the fossil fuel use and carbon
footprint of raised wood and slab-on-grade concrete,
the APA found that wood used considerably less fossil
fuel and contributed less to global warming than
concrete.
Efforts to reduce fossil fuel consumption and contain
global warming are affecting the way in which building
codes are created and shifting consumer needs. This
has resulted in greener building standards which
require significant reductions in energy consumption
from the building industry in every process from
creating building materials, to construction and on to the performance and life cycle of the building itself.
There are many ways in which wood can help to reduce fossil fuel consumption in the construction
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industry, some of which include:
•Forests act as carbon sinks as growing wood converts greenhouse gases to oxygen, thereby
mitigating much of the CO2 emissions created when harvesting, processing and installing wood.
Young forests produce 1 ton of oxygen and absorb 1.4 tons of carbon dioxide for every ton of
wood produced.
•Wood can be diverted from the landfill to be burned in boilers which means that fewer fossil fuels
are required for heating.
•When compared with other construction materials, wood uses less energy for extraction,
transportation, processing, construction and maintenance.
•Wood is a better insulator than other building materials and can therefore add to the energy
efficiency of a building.
The suitability of wood to sustainability in construction has been established over time through Life Cycle
Assessment (LCA) studies. By considering the environmental impact of building materials throughout their
lifecycles, the LCA is able to compare the impacts of different building materials.
Using the LCA methodology, a 2004 CORRIM study compared the environmental impacts of two flooring
systems; one concrete slab-on-grade floor and the other a raised-wood floor. They conducted experiments
in a home in Atlanta Georgia where a warmer climate comes into play and another study in the colder
climate of Minneapolis. Both studies looked at flooring systems covering a 2,500 square-foot area in a
single-story residential home.
From the APA: “The CORRIM study found that the wood house was better for the environment than the
steel house in terms of embodied energy consumption, global warming potential, air pollution, and water
pollution. The study also showed that wood was favorable to its concrete counterpart in embodied energy
consumption, global-warming potential, air pollution and solid waste production.
The CORRIM study clearly indicates that the use of wood in both locations presents significantly less
environmental impact than the steel or concrete counterparts, making wood the most sustainable building
material over the lifetime of the product.”
The study mapped the lifecycles of the materials utilized in constructing the floors from the extraction
of raw materials, through production of construction materials, onto transport and the building of the
structure all the way through to the eventual demolition of the building at the end of its lifecycle.
What it found was that wood has less than half the global warming impact in a cradle-to-grave comparison.
From the APA: “Total energy consumption on a cradle-to-gate basis was comparable for the two flooring
systems; however, the fossil energy requirements for the concrete slab was nearly double that of the
wood floor. This is due in large measure to the utilization of biomass energy in the manufacturing of wood
products.”
When one considers the full cradle-to-grave lifecycle, the difference between the two flooring systems
becomes far more pronounced with the wood flooring system actually rendering a negative global warming
carbon emissions measurement whether the flooring ends up in the landfill or as boiler fuel.
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A second study by the Athena Institute found that increased wood use was linked to reduced fossil fuel
consumption and potential for global warming.
The demand for wood building products is what keeps forestation levels high. There is more land under
forest in the US today (about 1/3 of the land mass) than there was in 1920. That’s because the demand
for wood products encourages landowners to plant more than two billion trees a year. If the demand was
to drop off, landowners would find more profitable crops.
Manufactured wood products like OSB make even more efficient use of wood resources as they can be
manufactured from faster-growing trees. The wood-chip byproducts of manufactured wood products can be
used for paper or fuel and these products overcome many of the inherent defects which occur naturally in
wood.
From the APA: “Designers can order engineered wood products such as beams and headers to be
manufactured to the exact specification for the particular project, reducing jobsite waste and promoting
the maximization of resource efficiency. And the technological assurances of strength and stiffness mean
engineers can design using fewer structural components, and therefore less of the resource.”
Heavily Loaded Drywall Carts Damage Wood Panels And
Floor Systems
Drywall carts are used to ferry materials around
construction job sites. When these carts are
overloaded and traverse wood sub-flooring panels,
they can cause damage, especially when these
panels are wet from exposure to the elements.
If you consult the APA guidelines which can be found
in Table 1 of Voluntary Product Standard PS 2,
Performance Standard for Wood-Based StructuralUse Panels, APA Form No. S350 (download a free
copy here) you can get an indication of static load
capacities. While these findings don’t offer accurate
measurements of the performance of wood panels
on the job site, they can offer some guidelines as
to the maximum loads which should be allowed in
loaded drywall carts.
The general guidelines state that most panels can withstand a static load of 400 pounds when dry and
about 300 when wet.
The standard drywall cart has 2”x 8” wheels which result in a ½ sq. inch of contact area per wheel. Most
drywall carts have the capacity to haul 3,000 lbs or 750 lbs per wheel if the load is evenly distributed.
This is in excess of the standard capacities.
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Overloaded drywall carts can even exceed the design capacity of the entire floor system (joist species,
depth, span, spacing and subflooring) so care must be taken to avoid these kind of problems.
If you must haul large carts over your subfloor, try laying a second layer of panels over the first to augment
panel strength and to prevent damage.
Care must also be taken when stacking drywall on the floor system prior to installation. Drywall should
be laid on the floor with the long direction perpendicular to the floor joists. This will avoid overloading the
design capacity of the floor system.
Snow On Your Truflor
Question
I used your subfloor in my house but didn’t get it dried in
before we had a winter storm. Now there’s about 8 inches
of snow on the floor! Should I be worried?
Wayne Martin, Springdale, Arkansas
Answer
Thank you for the email and question Wayne. TruFlor is
an Exposure 1 rated panel. That means it will withstand
normal delays in construction without affecting the
structural properties. There may be some cosmetic
issues but not structural ones. Snow is not an issue.
Having said that, you should get that snow off the floor
using a shovel or broom before the snow melts because
that will create a lot of water and/or ice. Best practice
has always been to keep snow and water off the floor using a shovel, broom or squeegee as that certainly
minimizes the effects of weather exposure.
Any edge swell that may occur as a result of exposure can be sanded after the floor has completely dried
and the finished flooring is ready to be installed (don’t do any sanding before the floor has completely
dried as that may open the fibers to more moisture).
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Uneven Floors? Check What’s Happening Below
If your flooring isn’t level, the first course of action is to check
what’s happening in the subflooring system. I recently got a
call from a client complaining that the floor was uneven. To
rectify the problem, the flooring guy had given the OSB panels
a heavy sanding.
However, upon inspection we found that the two beams below
were not exactly the same depth which was causing the I-joists that were sitting on the beams to be at
different heights and that was the cause of the uneven floor – not the panels. When there is a problem
with the floor you should first check what’s below before starting to do any work or calling a supplier. In
this case the issue could have been corrected before any costs (sanding) were incurred. Always check to
be sure I-joists are square and aligned before installing sub-flooring panels.
Measuring Moisture In Osb Sub-Floor Panels
Knowing the moisture content of your OSB subfloor panel is an important indicator on whether
to proceed with other stages of the build,
especially if hardwood flooring is the next step.
You need to know that using a moisture meter
doesn’t give very accurate measurements with
OSB or other glued products.
The problem with using moisture meters with
OSB is that the adhesives/binders and waxes
skew the readings, making the use of specific
gravity as the calibrations basis unreliable.
One option that can help meters work better with OSB is to first calibrate the meter by checking a piece of
the same OSB that is known to be “dry” (OSB from northern mills is typically Aspen while southern mills
it’s Southern Yellow Pine). Then, with the meter properly adjusted to the “dry” OSB, check the sub-floor
that may have an elevated moisture content. Always take numerous readings in different areas in order to
provide an overall picture of the floor’s moisture content.
OSB (when produced) will typically have a moisture content (MC) in the 2% to 8% range but will certainly
increase in the field and definitely will be higher if exposed to rain or high humidity conditions. Even if the
panels (roof, wall or floor) are not exposed to rain, their MC will change as a result of the relative humidity
and (to a very small degree) temperature.
Contact your moisture meter manufacturer and ask them how best to calibrate their equipment for
use with OSB. Always follow the hardwood flooring manufacturer’s instructions – especially regarding
acclimatizing their product and the MC conditions required prior to installing the flooring so you can take
the appropriate steps for a problem free floor.
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Flooring Tips
Raised Wood Flooring Systems Reduce Flood Damage
As sea levels rise and severe weather incidences
increase, more residents along the North American
coast lines become vulnerable to flooding during
storms. One way to reduce the damage done during
flooding is to build homes that are above the flood
level. One option which is gaining traction is the
raised wood flooring system.
Benefits Of Raised Wood Flooring
Systems
Reduced flood risks: Homes with raised flooring
systems that are above the base flood elevation (BFE) not only get better protection against flooding,
they also enjoy a lower insurance premium. Studies show that homes that are 3 feet above the (BFE) pay
50% lower insurance rates for flooding. The National Flood Insurance Program (NFIP) requires every new
development to have its lowest floor elevated to above the BFE.
Reduced grading: If you have a sloped lot, the raised flooring system will reduce the need for the cut and
fill usually required and site drainage is easier and cheaper.
Better access: The crawl spaces allow for easier access to the utilities which also means future floor plan
changes or building modifications will cost less. The crawl spaces make it easier to check for and control
pests.
Fewer issues with soils: Raised wood flooring systems make correcting movement due to subsidence or
expansion of clays or organic soils easier and cheaper.
Faster build time: Concrete and masonry work does not have to wait for the plumbing to be installed and
inspected as is the case with concrete slabs. Builders also don’t have to wait for concrete curing and can
build through bad weather.
Reduced costs: Raised wood floors are cheaper than slab on fill according to the APA, especially in builds
where additional soil must be brought in to raise the slab.
Building greener: Using wood for a raised flooring system rather than concrete and steel is a more
sustainable building option. According to the APA: “Wood is a renewable, sustainable resource that is
manufactured in energy efficient processes that optimize use of renewable energy sources. In fact, in
a comparison of fossil fuel consumption associated with the materials for three floor systems – wood,
concrete and steel – the wood joist floor required the least amount of fossil fuel energy.”
Types Of Raised Wood Flooring Systems
Pier-and-beam foundations can be placed on spot footings or continuous footing the placement of which is
determined by the load-bearing walls and the capacity of the floor joists.
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Stem wall foundations consist of a masonry or poured concrete foundation wall around the perimeter of
the home which is supported by reinforced concrete footing.
Wood pile and pier foundation: Treated wood piles and piers are popular in coastal areas for a cheaper
way to attain the necessary height.
Wood stem wall foundation: Lumber-frame walls sheathed with structural OSB panels are placed on a
footing below grade with a concrete/block wall on the footing and then the wood stem wall.
Installing raised wood flooring systems in flood-prone areas can mitigate the damage sustained during
severe weather events and can help to reduce insurance costs which, over the lifetime of the mortgage,
more than pays for itself and adds up to significant savings for the homeowner.
Removing A Piece Of OSB Subflooring
Question
I need to remove a piece of tongue and groove OSB subflooring panel to get some wiring through to my
attic. What’s the best way of doing this?
Tom Delange
Answer
If the T&G OSB subflooring panel has been screwed in place, you will easily be able to remove a piece of
the OSB subflooring panel. If the subflooring has been glued and nailed into place, it will be more difficult
to remove a piece. In this instance, you may want to consider making holes through the ceiling below and
though the subflooring to feed the cables through.
If removing a piece of the OSB subflooring is the only option, use a circular saw to make a cut down the
long edge of the T&G between the sheets of subflooring. Make the cut 1/8 inch less than the thickness
of the OSB subflooring to prevent cutting the attic floor joist or truss bottom cord as this will damage the
wood framing.
Cut the T&G on the two long edges and carefully remove the fasteners and gently pry the OSB subfloor
panel from the floor joists using a pry bar. Do this carefully so that if you have missed a nail, it won’t
damage the panel.
If glue has been utilized, you may need to cut out each rectangle of the OSB panel between the floor joists
rather than removing the whole piece.
Complete your wiring, then cut and nail pieces of wood blocking under the longest edge of the subflooring
to replace the tongue you cut when removing the panel.
You can also take this opportunity to beef up your insulation in the flooring while you have the panel
removed.
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Flooring Tips
Installation Tips For Tongue And Groove Structural Panels
When installing structural panels, you should always
follow the manufacturer’s instructions. You can also liaise
with your design professional and consult The Engineered
Wood Association (APA) guide E30V which you can
download here. We have included some tips to keep in
mind when installing OSB wood structural panels.
•
Check that joists are perfectly uniform and
aligned. Provide ¾” expansion joints for sections of
panels that exceed 80 feet in length.
•
Install the T&G panels with the APA grade stamp
down. The grade stamps should face down so that all the T&G panels fit flush.
•Leave an 1/8” space between the 4’ ends of the panels (a 10d nail is a great space guide) and
lightly butt the T&G together.
•Fastener spacing should be according to local building code requirements, your design
professional’s specifications or the APA construction Guide E30V.
•Install structural panels with the major strength axis perpendicular to supports.
•Gluing is recommended and can add strength to the floor. Glue subfloor panels to prevent
squeaks and uneven flooring. Only glue two or three panels at a time so that they can be fastened
before adhesive hardens. Placing a small bead of glue in the T&G groove can add strength and
stiffness to your floor.
•Proper panel spacing allows for the natural expansion of flooring as it adjusts to the interior
moisture levels in the building. These spaces prevent squeaky floors, buckling and uneven
flooring. They prevent call-backs which are costly both in terms of time and money.
Here are a few other publications that can help with installation guidelines.
http://www.norbord.com/na/cms/wp-content/uploads/TT024.pdf
http://www.norbord.com/na/cms/wp-content/uploads/D4811-Minimize-Panel-Buckling.pdf
http://www.norbord.com/na/cms/wp-content/uploads/APA%20Construction%20Guide%20E30V.pdf
http://www.norbord.com/na/cms/wp-content/uploads/Storage-and-Handling.pdf
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Expansion Joints In Flooring
Expansion and contraction of your flooring system is a
given. Because they are manufactured from different
materials or different kinds of the same material,
your flooring and substrate will expand and contract at
different rates. Expansion joints give your flooring the
space it needs to expand without buckling or cracking.
Why use expansion joints?
The LRFD Specification (AISC, 1999) notes that
expansion and contraction are a consequence of
changes in temperature and moisture level. Expansion
joints provide space for these changes to take place without compromising any other aspects of the
building design; “Adequate provision shall be made for expansion and contraction appropriate to the
service conditions of the structure.” While ASCE 7-02 Minimum Design Loads for Buildings and Other
Structures (ASCE, 2002) states: “Dimensional changes in a structure and its elements due to variations
in temperature, relative humidity, or other effects shall not impair the serviceability of the structure.”
Expansion due to temperature changes and increased moisture content can cause buckling in your roof,
walls and flooring. Buckling in the floor can cause tenting of tiles, uneven surfaces, nail pops and other
problems. Expansion builds up over the whole floor and the longer the run, the greater the force exerted
on the flooring. Eventually, something is going to buckle or crack. If expansion joints are included in the
flooring system, they will contract to absorb the force and expand when the floor cools or dries.
How to use expansion joints
Expansion joints are filled with materials which allow for expansion and contraction. According to the Tile
Association, most commonly these include neoprene, urethane or polysulfide for flooring applications
where there is a lot of traffic (sealants in high traffic areas must have a shore hardness of 35). Where
traffic is not of concern, silicone is often utilized.
From the American Wood Council: “An expansion joint of at least one half-inch must be provided at
the edge of flooring strips adjacent to parallel partitions and exterior walls. The joint is covered by the
baseplate and toe molding.”
Expansion joints in flooring systems should be 0.2 to 0.3 inches wide and filled with permanently flexible
filler. Joints will be placed according to the manufacturer and design professional’s recommendations.
Joints should be placed more frequently where tiles or flooring is in direct sunlight or in areas that heat up
more.
Expansion joints are utilized in addition to the 1/8-inch subfloor panel spacing and may not be necessary
for smaller rooms. The necessity of expansion joints depends on the size, shape and conditions in the
room in question; follow the manufacturer’s recommendations. It is also recommended that expansion
joints be placed between rooms if different flooring will be used in the rooms or where conditions differ
greatly from one room to another.
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Tiling Tips: Prevent Bathroom Tiles From Tenting
Floors expand and contract with changes in moisture,
heat and season. This movement can pull tiles apart
creating cracks or push them together so that they pop
up or ‘tent’. Proper planning and preparation of the
subflooring will help to prevent tenting and cracks in tiled
bathroom floors.
Subflooring Panel Spacing
Bathroom tiles can be installed over 23/32” OSB
subflooring panels. These panels must be supported
by 16” o.c. joist spacing. OSB panels are an excellent
base for bathroom tiling as they help to provide an
even surface to keep your tiled bathroom floor pristine. OSB subflooring panels must always be installed
with 1/8” spaces between panels to account for movement caused by expansion and contraction and to
prevent tile tenting.
Prior to installing the OSB subflooring, ensure that all the joists are square and level and align the OSB
panel’s strength axis perpendicular to the joists. This will provide strength and rigidity and minimize tile
tenting.
Tiling Tips
Don’t couple all the membranes underneath the tile. Leaving membranes uncoupled will allow for
expansion and movement.
If your bathroom gets a lot of direct sunlight, use lighter, smaller tiles. Large, darkly colored tiles absorb
more heat and this causes more movement. More grouting with smaller tiles also allow for movement
without cracking or tenting.
Don’t put thinset or grouting around the edges of the tiles where they meet the walls as this will leave
space for them to move without compromising the floor.
If you are installing a steam shower, use a special thinset that will allow for rapid thermal expansion.
In large tiled rooms, install expansion strips and use grouts and thinsets that are designed to handle
expansion and contraction.
Tile your bathroom last to prevent cracking when tools or construction materials are dropped on the floor.
Do not walk on the floor until the mortar and grouting have dried. When installing a tiled bathroom floor,
always follow the tiling manufacturer’s instructions and the recommendations from the Tile Association.
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Creating the perfect crawlspace
The best way to design a crawlspace that accentuates
your building envelope and does not allow unwanted
moisture into the home is to treat them as if they were
miniature basement spaces. Crawlspaces should be
insulated, sealed and all exposed masonry should be
covered to prevent condensation.
From the US Department of Energy: “Most building
codes require vents to aid in removing moisture from
the crawl space. However, many building professionals
now recognize that building an unventilated crawl
space (or closing vents after the crawl space dries out
following construction) is the best option in homes
using proper moisture control and exterior drainage techniques.
If you have or will have an unventilated crawl space, the best approach is to seal and insulate the
foundation walls rather than the floor between the crawl space and the house. This strategy has the
advantage of keeping piping and ductwork within the conditioned volume of the house so these building
components don’t require insulation for energy efficiency or protection against freezing. The downside of
this strategy is that rodents, pests or water can damage the insulation, and the crawl space must be built
airtight and the air barrier maintained.”
Seal crawlspaces with a vapor barrier along the floor and walls that is at least 6-mil or more. This will
prevent moisture from entering the home, termites from gaining access to lumber and soil gases from
leaching into the flooring system. Attach the vapor barrier mechanically at the edges and seal all seams
with tape. Consider installing a thin 2-3 inch concrete slab over the vapor barrier for increased insulation.
Where crawlspaces are below grade, they must have perimeter footing drains to move moisture away from
the home. All crawlspaces should provide adequate drainage for any floods or plumbing issues that may
be experienced. Always ensure that the grade slopes away from the foundations.
Crawlspaces can be conditioned or vented. Vented crawlspaces allow air to move through, but care must
be taken with the design to ensure that moisture and water is kept out.
Conditioned crawlspaces must be included as part of the homes heating and cooling systems so that
they stay dry and maintain the same temperature as the house. This would mean heating and AC for extra
cubic space and possibly larger equipment to handle it. Conditioned crawlspaces also need to be vented
through pipes and require a blower fan to circulate air.
In homes where radon is a hazard, you can vent your crawlspace with perforated plastic piping in the
gravel under the vapor barrier. Run the piping up through the roof to ensure that the radon is safely
vented. You can also control radon by installing a passive radon system in the crawlspace floor.
If your crawlspace has been exposed to moisture during the construction process, it will need temporary
dehumidification. Never utilize your crawlspaces as storage and regularly check that crawlspace
perimeters are secure in order to prevent animals, moisture and insects from entering.
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Flooring Tips
Installing Ceramic Tiling Over OSB Subflooring
OSB panels provide an excellent base for many types of finished flooring including ceramic tiles. Careful
attention must be paid to the construction and preparation of the subfloor in order to avoid costly
callbacks. Planning and patience along with these tips will help ensure that you install the quality of
finished flooring you are looking for. Always follow the manufacturer’s installation instructions and/or the
Tile Association’s recommendations.
Ceramic tiling can be installed onto 23/32” OSB subflooring panels where the panels are supported by
16” o.c. joist spacing. Manufacturers generally recommend that the deflection of the subfloor system
be limited to no more than span/360 under total load. The joist depth, spacing and deflection may vary
depending on what type of product is being used and the loads the system will be required to carry, so
always check with your tile manufacturer and design professional prior to installing your subfloor system.
A designer will take all the factors that affect the dead and live loads into consideration to establish what
the floor system requirements are.
When installing the osb subflooring system, check that the joists are square and level. Align the
panel’s strength axis perpendicular to the floor joists to provide optimum rigidity to the flooring system
and to minimize the possibility of cracked tiling.
Ensure that the OSB panels are adequately spaced with the required 1/8” spacing at panel ends. This
gap allows for expansion due to changes in moisture conditions and can prevent buckling and uneven
floors.
Inspect the subflooring panels prior to installation of the ceramic tiles. Ensure that the subflooring is
correctly fastened to the joists and that the fasteners are not overdriven. There should be no fasteners
sticking up above the subflooring surface. Sand any uneven areas that may cause issues. Ensure that an
adequate vapor barrier and proper ventilation have been installed in crawl spaces to forestall any moisture
issues.
To ensure the longevity of your ceramic tile flooring, it’s important that the subflooring system be as
rigid as possible. This can be accomplished with the use of thicker subflooring panels, cross bracing
and underlayment with a closer fastener pattern. Applying adhesive to the joists and a small bead in
the groove (a PL400 sub-floor adhesive is the best choice) will also help to improve the rigidity of the
subflooring system. Apply glue only 2 panels ahead of the installation to avoid the glue setting before you
are ready.
To prevent your ceramic tiles from cracking, do not apply any weight to the floor until all mortar has
properly dried. Tiling should be one of the last tasks completed on the building site to prevent chipping
and cracking.
Remember it’s the entire floor system that supports your tile and not just the OSB.
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Flooring Tips
Installing OSB Wood Panels Over Concrete
OSB structural wood panels can be installed over
concrete slab floors for both commercial and residential
applications. The panels can be installed directly onto
the concrete slab, over sleepers which are installed
onto the concrete slab or over rigid foam insulation.
The efficacy of these methods is reliant on the proper
installation of an appropriate 6 mil polyethylene vapor
barrier which prevents moisture inherent in the concrete
slab from transferring to the flooring installation above.
Wood Flooring Panels On Concrete
In order for this application to be successful, the
concrete slab must be level and free of flaws. To ensure an even floor, a topping layer of gypsum concrete
or lightweight concrete can be poured over the concrete slab, but must be allowed to cure sufficiently prior
to flooring installation.
The flooring system can be glued directly to the concrete slab, but here adequate pressure must be
applied during curing. Where vapor barriers are installed over concrete slabs, mechanical fasteners must
be used to attach the flooring system to the concrete slab. The expense of this kind of installation can be
prohibitive.
With new construction, install a 6 mil. polyethylene vapor barrier under the concrete. If it is unknown
whether that barrier exists under the concrete, allow the concrete to completely dry (could take from 6 to
18 months) and use a vapor barrier with the new floor.
Wood Flooring Panels Over Sleepers
OSB flooring panels over 2×4 sleepers is one of the most cost-effective ways of installing a flooring
system over a concrete slab. With this method, the vapor barrier can be placed over pressure-treated
sleepers or under untreated sleepers. Here the sleepers must be attached to the concrete slab with
mechanical fasteners and/or adhesive (use an adhesive that meets construction standard ASTM D3498).
Insulation can be incorporated between sleepers. Sleepers can be installed so that they are level, thus
overcoming flaws in the concrete slab and providing a straight, even surface on which to place the flooring
system.
Ensure adequate spacing between panels and between panels and walls to accommodate wood panel
expansion in varying moisture conditions (this is especially important below grade). Adequate panel
spacing can reduce or eliminate panel issues and uneven flooring. This is especially important for belowgrade slabs where moisture is of greater concern.
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Flooring Tips
Wood Flooring Panels Over Rigid Foam Insulation
Applying OSB flooring over rigid foam insulation (must be at least 1-inch thick) helps to keep flooring even
and provides excellent insulation. If using a single layer of panels, prevent differential deflection and
potentially crushing the foam by backing the square edges of panels with splice plates. If you don’t want
to use splice plates, install a double layer of square-edge panels with joints and seams offset or use T&G
sub-floor panels to distribute the loads.
Avoid overdriving mechanical fasteners as this will crush the foam insulation and potentially damage the
concrete below. Where foam is compressed under fasteners it can, over time, cause nail popping which
can result in a squeaky floor.
Pressure-treated lumber must be used where lumber is in direct contact with the concrete slab and
waterborne ACZA or ACQ treatments are recommended with a preservation retention level of at least 0.25
lbs/ft2. The preservative treatment should be 3B or higher; download the APA technical notes for this
application here. Allow concrete to sufficiently cure prior to flooring installation.
Wood Structural Panels Over Above-Grade Concrete Floors
Concrete slabs can take 6 to 18 months to properly cure. When installing wood structural panels onto
concrete that is still ‘green’, use the methods discussed above.
Installing APA-rated wood flooring panels over sleepers is the recommended installation method. It
provides the most benefits and is also an economical choice. Always provide adequate panel spacing,
always use an appropriate vapor barrier and use pressure-treated wood below any vapor retarder.
Drilling Drainage Holes Into Truflor Subflooring
Question
Can you tell me if there are any potential issues with
drilling 1/2” holes in “TruFlor” subflooring in order to
drain stagnant rain water…?
Dean Magee
Answer
Thank you Dean for your email and your very good
question. First, let me say that there are no issues with drilling a hole to allow water to drain away. Having
said that you need to consider “where to drill” and avoiding high traffic areas such as the center of a hall
or the center of a door way would be a best building practice. In a closet or close to a partition would be
ideal as opposed to the center of a room.
Generally a broom or squeegee is used to move the water towards the hole. Take a look at this APA (The
Engineered Wood Association) file that covers that topic on page 2 along with a suggested repair method
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after everything has dried completely. Drilling a hole will not affect the structural properties of the subfloor. Just an FYI that you may see some edge swell. That is typical of commodity OSB and plywood when
panels have been exposed to rain. The floor should be allowed to dry completely before attempting to
sand any joints. Do any sanding that might be required just before the finished floor is to be installed.
Installing Hardwood Flooring Over OSB Panels
Hardwood can make for a durable and beautiful floor,
but small mistakes in the subflooring or installation can
wreak havoc resulting in buckling, squeaky and uneven
floors. Taking time for adequate preparation work prior
to installation will ensure that small underlying issues
don’t telegraph through to the floor above. While this is
not a definitive guide to hardwood installation over OSB
panels, here are some essential guidelines to hardwood
flooring success.
Preparing The Site
Hardwood flooring should always be one of the last things to complete on site. Hardwood floors can only
be installed in areas which are enclosed. In order for the wood to acclimate, the HVAC system needs to be
operational or a temporary HVAC system should be installed which simulates the conditions of the actual
HVAC system during occupancy. The same temperature and humidity conditions that will exist during
occupancy must be created during installation.
Check the manufacturer’s recommendations on whether the flooring needs to be acclimated onsite. Where
this is necessary, run HVAC systems for five days to ensure that conditions in the building are the same
as they will be during occupation.
Check the hardwood flooring for moisture content when it arrives so you have a baseline for acclimation.
Check at least 40 boards for every 1,000 square feet of flooring. Follow the manufacturer’s guidelines on
the correct moisture content for your installation. This is usually 4% difference for solid strip flooring and a
2% moisture difference for wide-width solid flooring.
If the manufacturer recommends acclimation, ensure that the humidity and temperature conditions are
identical to those that will be experienced during occupation. Cross-stack the wood with 1-inch spaces
between the boards to allow for air circulation on all sides. Boards should be acclimated for about
three days or until the manufacturer’s recommendation for moisture content has been achieved. Some
tropical exotic hardwood varieties may require longer acclimation periods. Always follow manufacturer’s
recommendations first and maintain the conditions in the building prior to, during and after installation in
order to validate the manufacturer’s warranty.
Once the hardwood flooring has been installed, allow an additional 5-7 days for acclimation prior to
finishing. Follow the manufacturer’s recommendations here as well as the recommendations for flooring
adhesives as some kinds may need longer periods to set prior to finishing.
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Flooring Tips
Crawl Space Preparation
The basement and crawl spaces should be dry and complete prior to the hardwood flooring installation.
Crawl spaces should have a minimum of 18 inches from the ground to the subflooring joists.
The crawlspace earth or concrete slab should be covered with a vapor barrier to prevent moisture from
reaching subflooring. Where crawlspaces aren’t ventilated, the vapor barrier seams should overlap by 6
inches and the vapor barriers should extend 6 inches up the stem wall to which they must be securely
attached.
Crawl spaces should be adequately ventilated with 1.5 square feet of ventilation per 100 square feet of
crawl space or in accordance with local building codes which may differ from one region to another.
OSB Subfloor Preparation
Ensure that the subfloor is flat, clean, dry and that there is no movement in the subflooring system.
Hardwood flooring will not stabilize the OSB subfloor, so all movement must be remedied prior to
hardwood installation.
Ensure that no fasteners are exposed or raised and that there is at least an 1/8-inch gap between OSB
subfloor panels.
Moisture contents of OSB subflooring must be established prior to hardwood flooring installations. Take
at least 20 moisture readings per 1,000 square feet of subflooring. High readings in an area can signify a
problem. The moisture content of OSB subfloors can be tested with pinless or probe moisture meters.
Consider installing a vapor barrier over OSB subflooring panels. Vapor retarders help to prevent moisture
transfer may reduce noise, dust and the impact of seasonal humidity changes.
Where vapor retarders are installed, overlap seams by 4 inches. Vapor retarders must have a perm rating
of 0.7 or more; anything less may trap moisture in the subflooring system.
Types Of Subfloors You Can Use Under Hardwood Flooring
When it comes to hardwood flooring, the quality
of the installation will be determined by the
quality of many things including the choice
of subflooring and the condition it’s in. Even
the slightest imperfections in your subfloor
can telegraph into the flooring and result in
squeaking, buckling and uneven floors. No matter
which subflooring you select, ensure that it is
flat, clean and dry before you begin installing
your hardwood floor.
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Flooring Tips
While you should always adhere to the manufacturer’s installation instructions, there are some general
guidelines provided by the NWFA that apply to most subflooring installations. There are a number of
subflooring options available and you can speak with your design professional to find one that suits your
climate, needs and budget.
OSB and plywood subflooring panels
These are popular and economical options for subflooring. Both OSB and plywood panels offer excellent
strength and durability.
It’s imperative that the joists be inspected prior to installing plywood or OSB panels to ensure proper
installation techniques have been followed and that all joists are flat, level, clean and dry. Do not step on
joists when you are installing the subflooring panels.
As the plywood or OSB wood panels acclimate to the new environment, their moisture content will change.
Store plywood and OSB properly on site to protect them from the elements and allowed to acclimatize to
the conditions the floor will see when in service.
Use a moisture meter to measure the moisture content of your subflooring wood panels prior to
installation. Take a minimum of 20 readings per 1,000 square feet and document readings to show that
you followed procedure. Moisture meters provide readings from the highest moisture conditions they come
in contact with and not an average. Taking more readings will help in confirming whether or not the subfloor is dry enough to install the flooring.
Allow for a 1/32 inch gap between panels when installing to accommodate swelling with increased
moisture content.
Sub-flooring must be installed with the strength axis perpendicular to the flooring joists.
Do not use sealer or drywall compound to fill cracks and dents in the sub-floor as this may deteriorate
over time.
Ensure that the subflooring panels are flat. Sand any joints that have raised edges because of edge swell.
Use a moisture-vapor retarder between the subflooring and the hardwood flooring to prevent moisture from
leaching through the joists and subfloor to negatively affect the hardwood above.
Concrete Slabs
This is a popular subflooring option in the southern states and in areas where homes do not have
basements.
Some manufacturers do recommend installation of their products for glue-down applications over slabs,
provided that a moisture-vapor retarder is installed. In these applications, the concrete must be of a
sufficient weight (3,000 psi). If you are utilizing lightweight concrete, plywood or OSB subflooring panels
will have to be installed.
If you are installing subflooring over the slab, consult your hardwood manufacturer to determine if you
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Flooring Tips
should install a sleeper system or a floating, glue-down or nail subfloor.
The slab should be flat prior to flooring and subflooring installation (usually 1/8” in a 10-foot radius).
Most brands of hardwood flooring can be installed over concrete when plywood or OSB subflooring panels
have been installed over the concrete slab but it’s wise to consult the manufacturer for any specific
installation requirements.
How To Fill The Chips In Your Subfloor
Question
My new house has a TruFlor subfloor. Some of the panels
had slight damage at the edges leaving me with a couple of
spots where there is a “chip” (maybe 4” x 1” x 1/4” deep). I’d
like to fill and level these areas before installing my flooring
(hardwood in one area, carpet in another). What would you
suggest I use as a filler?
Cal Stanley, Grey, ME
Answer
Thank you for your e-mail Cal and your question (I’ve never
been asked that before). I think this should work. A wood
putty should do the job; just be sure to put in on in layers so
it can dry properly before adding more. People who build cabinets and need to fill a hole will mix sawdust
and carpenter glue so that may work. Don’t use a drywall filler as that will likely break up over time. The
hardwood flooring should easily span that without an issue.
I-Joist Installation Tips
I-Joists are engineered wood products that are gaining
popularity with building professionals. Engineered I-Joists
are manufactured under exacting conditions to ensure
consistent strength that provides long span and high load
capabilities. These installation tips are supplementary to
your manufacturer’s instructions and technical guides.
Load handling: Each I-Joist must be braced and nailed
using appropriate joist hangers, blocking panels and
Rimboard or bridging at the joist ends. Use a minimum of
1×4 temporary bracing during installation to prevent I-Joists
from buckling. Do not place any loads on I-Joists until
properly braced and sheathed.
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Rim framing: This is the suggested installation method as it encloses the floor perimeter and transfers
bearing wall loads to the wall below rather than the I-Joist ends.
Blocking is utilized for load transfer. There are two kinds of blocking that can be used:
1. Blocking between joists which is utilized at interior supports near a load-bearing wall and where floor
joists do not span over supports.
2. Loads are transferred around I-Joists with squash blocks. Squash blocks help to divert loads from
posts and columns.
Span capabilities and nailing patterns: These vary by manufacturer, so consult your design professional
or manufacturer’s span chart to determine span capabilities and nailing patterns.
Storage and handling: Always stack I-Joists upright and level. Protect I-Joists from the weather and keep
off the ground. Follow the APA guidelines for on-site lumber storage. Avoid stacking construction materials
over unsheathed joists. Do not lift I-Joists by the top flange. Leave bundles wrapped until ready for
installation.
Modification of I-Joists: While I-Joists can be cut to required length, do not cut, notch or drill flanges.
Modification is discouraged as I-Joists are engineered to transfer floor loads to the joist supports and
carry very high loads. When they are modified, their efficacy cannot be guaranteed. If an I-Joist has been
damaged, do not attempt to repair it.
Web stiffeners: These wood blocks are utilized to reinforce I-Joists where there is a danger of buckling or
where the webs are in jeopardy of slicing through the flanges due to excess loads. They can be made from
rim board, OSB board or lumber. They are also used where I-Joists are supported in hangers that do not
stretch to the top of the flange. With the top of the I-Joists unsupported, it can move laterally which would
twist the top flange.
Web stiffeners can be designed for bearing or load. Bearing stiffeners are used at both interior and
exterior while load stiffeners are located between I-Joists where point loads greater than 1,500 lbs. are
applied to the top of the flange.
Web stiffener depth should equal the distances between I-Joist flanges less ¼ inch.
For bearing stiffeners, this gap will be positioned between the stiffener and the bottom of the top flange.
For load stiffeners, this gap is positioned at the bottom of the stiffener.
Can I Glue Vinyl Planks Directly To My Subfloor?
Question
Can my flooring contractor install vinyl planks by gluing them directly to the Truflor subflooring material?
Adrian, Fort Lauderdale, FL
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Answer
Thank you for your email Rick. An underlayment is required under vinyl to avoid telegraphing of any
variations in the sub-floor. Hardwood flooring or carpet can be installed without an underlayment but vinyl
requires it.
See http://www.norbord.com/na/cms/wp-content/uploads/APA%20Construction%20Guide%20E30V.pdf
for the APA E30V document which contains the relevant guidelines. In there you will find info on the correct
way to install underlayment.
Underlayment Installation Tips
If you are laying sheet vinyl or vinyl tiles over your
subfloor, a layer of subfloor underlayment will need to
be installed. It’s imperative that your underlayment
is installed correctly and remains pristine; any dents,
bumps, nails or edges will show through the flooring.
There are some tricks you can employ to ensure that
your underlayment layer is properly installed.
Choose the right materials
Select underlayments which have been APA approved
or approved by your finished flooring manufacturer.
If you are using plywood products, they must be manufactured using water-resistant resins as this will
ensure your underlayment’s ability to withstand moisture. Check that your plywood panels aren’t damaged
and are smoothly sanded.
Always allow underlayment panels to acclimatize by standing them on their edge in the room where they
will be installed for 24 hours. If they have to spend some time on the site prior to installation, ensure that
they are properly stored. Only install underlayment onto dry subflooring. Moisture in the subflooring may
cause your underlayment panels to expand beyond their 1/32 gaps which will also lead to buckling.
Ensure that your subflooring is straight and even; mistakes here will affect the underlayment.
Right side up
Ensure that the panels are installed with any grade stamps facing down to avoid the possibility of inks
bleeding through the finished flooring.
Leave a gap of 1/32 inches between panels to accommodate the potential swelling of panels as their
moisture content changes. Failure to implement correct panel spacing may result in uneven flooring and
buckling.
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Flooring Tips
Installation tips
Underlayment panels should be installed with the long direction, or strength axis, perpendicular to floor
joists, never parallel to the subfloor seams. All panel edges should be staggered at least 2 inches to the
subfloor seams for increased stability.
Today’s vinyl floors show every imperfection so nail holes and sunken edges must be filled in with hard,
quick-setting filler appropriate to the kind of underlayment you have selected. Ensure that the filler has
cured completely before laying the flooring. Sand the filler to prevent bumps showing through.
Schedule underlayment installation as one of the last things you need to do so that the panels are not
damaged. Consult the APA document for guidelines on underlayment installation and for fastener spacing.
Melting Ice On Osb Sub-Floor Paneling With Calcium
Question
During a recent snowstorm, the contractor used calcium to melt the ice that had formed on the TruFlor
sub-flooring panels. Are there any issues with this method of melting ice that he should be aware of? What
do you recommend?
E. Raymond, NH
Answer
Thank you for the question Edward. I took your question to the APA for expert advice and below is the
reply:
“Although most common salts and salt solutions have no significant effect on wood, certain highly acidic
or alkaline solutions may reduce its strength. Calcium chloride is slightly acidic which should not affect
the strength properties of wood structural panels. Reference APA Research Report 132 (pages 16 & 17).
We discourage use of ice-melting salt(s) due to concerns regarding corrosion of fasteners and connectors
exposed to calcium chloride or sodium chloride. We would expect the corrosion rate to increase as a
result of such exposure (it is also possible that pitting corrosion will occur). If exposure is limited or short
term in nature, engineering judgment may be that significant concern is unwarranted.
A Handbook of Chemical Engineering shows that at concentrations of 50% and at a temperature of 100 F,
calcium chloride can corrode steel at a rate of 0.02” per year. These conditions would be the extreme end
of floor exposure.
Calcium chloride is a water absorption agent, which if it gets into the wood fiber could promote water
absorption by the OSB sub-floor and prolong the drying process. This could lead to increased corrosion
risk.”
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