A recent thread on underpinning brought a question back to mind that's I've been wondering about for a while. Not that I'm planning on doing any, just one of those things that's piqued my curiosity.
When removing and replacing a few bricks, or underpinning a section of wall, what does that do to the distribution of stresses in the wall ?
Replacing a brick (or a few bricks) first.
Assuming everything was reasonably well built, I'd expect the stresses in the wall to be some approximation of uniform. If you take a brick out, the load will transfer to those around it. When you refit it, I can't see that you'll be able to apply any 'preload' to the cement - so presumably you end up with a brick that's effectively doing nothing unless something else gives a little afterwards ?
With underpinning, you've taken out a large section of support - so quite a bit of load to transfer to the surrounding sections. Presumably in this case, as you work along the wall, the whole thing sinks a little (and I mean only a little) when you take a section out and the new bit next to it takes up the load and gives a little ? If you get it wrong, is there a danger of getting a crack diagonally up the wall ?
When building a whole house in one go, I'd assume the foundations will settle gradually as you add weight, so there'll be some variation in load - but by the time you get to the top I'd have thought it would have sorted itself out, and the lower levels will have a fair old load on them.
When removing and replacing a few bricks, or underpinning a section of wall, what does that do to the distribution of stresses in the wall ?
Replacing a brick (or a few bricks) first.
Assuming everything was reasonably well built, I'd expect the stresses in the wall to be some approximation of uniform. If you take a brick out, the load will transfer to those around it. When you refit it, I can't see that you'll be able to apply any 'preload' to the cement - so presumably you end up with a brick that's effectively doing nothing unless something else gives a little afterwards ?
With underpinning, you've taken out a large section of support - so quite a bit of load to transfer to the surrounding sections. Presumably in this case, as you work along the wall, the whole thing sinks a little (and I mean only a little) when you take a section out and the new bit next to it takes up the load and gives a little ? If you get it wrong, is there a danger of getting a crack diagonally up the wall ?
When building a whole house in one go, I'd assume the foundations will settle gradually as you add weight, so there'll be some variation in load - but by the time you get to the top I'd have thought it would have sorted itself out, and the lower levels will have a fair old load on them.
