Iron rusts. When it does so, it expands something of the order of 25 times its original thickness. That means that if a rusty bit of iron in an old building rusts, it can jack up a wall. A one inch gate pin can lift a wall by several inches.
We see problems with rusty iron in historic buildings quite a lot. Common things to look for are shattered stones - with radial cracks around the iron. Shattered stones on parapet walls - where iron cramps have expanded and broken the capstone. Commonly we see a problem in places like Bristol and Bath, where stonework around windows is exploding because iron pins have been used to hold the stone mullions and transoms together.
The photos here show a Yorkshire property in which a gate pin has rusted and jacked the building apart.
It is knowing and understanding things like this which sets us apart from other Historic Building Surveyors - we know what Listed Buildings have within the fabric - what to look for when we are doing Building Surveys - so we will hpefully find and point out issues such as these!
This garden wall has been jacked up by rusting iron gate pins - it is now unstable and needs rebuilding..
And this is the rusty iron jacking the wall in the photo above. It was originally a thin band of iron about 6mm thick - now it is nearly 50mm thick. It has destroyed the wall.
Another gate pin - rusting in a stone building, and jacking the entire wall
Here you can see the cracking in the wall, caused by a rusting iron gate pin.
A Grade 2* Listed building on a small Estate. It is on the Buildings at Risk register. The owners had several surveys to determine what was wrong. None gave answers. We were asked as Historic Building Surveyors to have a look and within minutes had diagnosed the issues. Iron pins and bands have all but destroyed the stone and forced the building apart. Removal of the iron, and careful cramping of the building to bring it back together will restore it to its former glory. The main house is Grade 2 listed, and one of those places I wish I'd seen when it came on the market - I'd have bought it straight away!
