Building Technology
Restoring damage in cross-vault
When I study one of the old buildings, I note this problem, the photo shows the top of cross vault, this situation is very dangerous because the roof will fall and be damaged at any time. For all restoratives, how we can restore this roof, and what are the best restoration materials we can use to restore the big damage in cross vault.
Muneer Elbaz
Restoring damage in cross-vault
You call this dome shape a cross-vault. Is this a cross-vault made of stone?

From the look of the hole, the keystone and maybe some surrounding stones have fallen. Are these stones missing, or are they lying on the ground below?

If this vault is of stone, to repair you need to (a) make detailed drawings of all of the existing stones. To determine whether it is possible to replace the hole with a keystone, and then either get a new keystone made from stone from the original quarry, Or, perhaps make a new keystone from concrete.

(b) support the whole dome from below and carefully clean away loose mortar. then replace the keystone making sure that the load-bearing surfaces of the keystone duplicate the angle of the other stones in the vault.
Frank John Snelling
Restoring damage in cross-vault
Dear Muneer,

You need to give more details of this 'vault' to extract a precise answer. The photograph is not very clear. Although, as Mr. Snelling points out, it seems the keystone and some neighbouring members have collapsed.

What is the material for this 'vault'? Since when is it in this present dilapidated state? What is the support condition for this 'vault'? What is the cracking pattern, if any? What is the loading over this vault, if any?

Whether the problem is local (limited only to the vault) or of a larger structural concern (on account of movement of supports) is important to realise. The material used and its behaviour is also important to ascertain the solution.

If it is confirmed that this is only a local problem (most probably on account of some 'human' intervention like vandalism) then what Mr. Snelling suggests may work. But, first make sure that is the case.
Shubhru Gupta


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