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MRP Work: Step by Step

Newly carved cross being fixed onto the Cathedral

Each Major Repair Area (MRA, see Major Repair Programme page for more information) that the Salisbury Cathedral Stone Masons, Conservators and Glaziers work on has the same schedule of work;

 

   

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.

 
   
Scaffolding: This is then erected to the elevation at suitable lift heights (distance between the levels) so we can gain access.  
   

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.

 
   
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.  
 

 

 

Scheduling:  The "blank canvas" (see Photogrammetry) CAD drawing of the elevation is taken onto the scaffold 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 in the right place.

 

 

 

   
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

 

 

 

   

  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 (see the Sawing section). 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.

 

 

   
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.  
   

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.

 

 

   

Masonry conservation: One of the last stages towards completion (more detail in the Conservation section);

 

 

   

Plumbing:: Rainwater goods (i.e. gutters and downpipes) and roofs are all worked on if necessary (more detail in the Plumbing/Leadwork section).

 
   
 Carpentry: Window frames are repaired or replaced; timber in the roof spaces are worked on if structurally unstable (see more detail in the Carpentry section).  
   

Glazing works:  Once the risk of flying stone dust and splashes of conservation coatings has passed, the Areas are finalised with any glazing work (more detail in the Glazing section).

 
   
  “After” photography: This is exactly as it sounds and serves as a visual record of the work undertaken.