MRP Work Step by Step
For each Major Repair Area (MRA – see Major Repair Programme page for more
information) that the Salisbury Cathedral Stone Masons and Glaziers work on, the schedule
of work is the same;
1. Photogrammetry;
2. Scaffolding;
3. Cleaning;
4. Pre-photography;
5. Scheduling;
6. Mould cutting;
7. Sawing;
8. Masonry banker work;
9. Stone fixing;
10. Masonry conservation;
11. Plumbing;
12. Carpentry
13. Glazing works;
14. “After” photography.
Each step is explained further below:
1. Photogrammetry: This is taking a sequence of overlapping photos from a
suitable distance, then applying them to a CAD (Computer Aided Design) and
producing a drawing of the elevation or ‘face’ of an area; this is then our blank
canvas from which to work.
2. Scaffolding: This is then erected to the elevation at suitable lift heights
(distance between the levels) so we can gain access.
3. Cleaning: This involves a light clean using a JOS system, which is similar to
pressure washing, but is done with a mixture of air, a fine inert powder and a
small amount of water and will eliminate lichens and algae. It also takes off the
loose soot crust that has built up over the centuries thus exposing the natural
stone for surveying.
The JOS System in Action
Stonework before and after cleaning
4. Pre-photography: This is when close-up photographs are taken of each of the
sections of the MRA to see the extent of damage to the stone work.
5. Scheduling: The “blank canvas” (see “Photogrammetry”) CAD drawing of the
elevation is taken onto the scaffolding and the Head Stone Mason, along with
the Cathedral Architect, then mark up the drawing to show the most badly
decayed stones that need replacing. The stones to be replaced are also
numbered for ease of reference and to ensure the right one is put back in the
right place.
Also scheduled are stones that just need conserving rather than replacing; these will get
marked in green, denoting conservation only.
6. Mould cutting: Once all the relevant coloured drawings have been approved,
the Stone Masons can access the scaffold and start taking templates for the
replaced stone; this process involves cutting through joints and working the
faces off the old stones…
…in order to draw around them using plastic templates and use complex
geometry to set the measurements of the stone out on job cards.
7. Sawing: The Sawyer selects stone of the relevant hardness and cuts it to the
correct size, ready for the more detailed work to be undertaken by the Masons.
There are a set of templates for each stone, which are then applied to the
sawn block and scribed on with a tungsten point to create the 3D image.
8. Masonry banker work: The stonemason then works the stone to the required
template in the traditional way using mallet and chisels. The term “banker”
derives from the name of a bench of timber or stone (may be a single block) on
which stone is worked.
9. Stone fixing: A term used in Europe to describe the installation of stone work
when the newly worked stones are put back into the building.
These two pictures show newly worked stones in place with some joints still in
need of pointing. Note also in the first picture the gap about a third of the
way along at the top where the relevant stone has not yet been fixed.
10. Masonry conservation: One of the last stages towards completion;
11. Plumbing: Rainwater goods (i.e. gutters and downpipes) and roofs are all
worked on if necessary;
12. Carpentry: Window frames are repaired or replaced; timber in the roof spaces
are worked on if structurally unstable;
13. Glazing works: Once the risk of flying stone dust and splashes of conservation
coatings has passed, the Areas are finalised with any glazing work;
14. “After” photography: This is exactly as it sounds and serves as a visual record of
the work undertaken.