Repairing an Oxford College

 We started the year by welcoming Michael Gray to our monthly talks in January when he gave us an insight into considerations made when repairing an Oxford college. The college in question being All Souls College Oxford whose foundations were laid in 1438.

The building is Grade 1 listed and although it looks dirty because it's on a bus route and exhausts emit bituminous deposits which can be seen to affect the lower part of the building.

I have lost the ability to delete pictures, so this window appears twice. What we're looking at is horizontal cracks appearing, seen near the bottom of the photo.

Below you can see the erosion on these 4.5m tall chimneys, decisions have to be made about whether to make replicas and insert them into the chimney or try and repair them in situ

In this case, as can be seen below, it was decided to make a new section to fit into the chimney

When All Souls College was 700 years old, in 1835, the facade was rebuilt, local stone had run out in 1825 and stone was sourced from Lincolnshire

Above you can see where stone has been replaced, joints are 2/3mm and this makes for a very tight fit.

Below you can see the after on the left and before cleaning on the right. Cleaning is achieved with 1mm jet washing at high temperatures. Another method is to put clay onto the stone and cover it with clingfilm and leave it to absorb the bituminous deposits.

While the work on the building was being done, it was covered in scaffolding, guests at the £430 per night hotel opposite weren't impressed with the view of the scaffolding.

This extremely interesting talk by Michael Gray was not recorded because of the difficulty of obtaining permissions for the photographs.