How do they do it? Why doesn't the wall suffer from weakness?

[u587162]

Cjard,
Fantastic explanation, thank you. One of the best answers to my questions on this site. And who said diynot doesn't do science lessons

Were you once a physics teacher who got bored with the long summer holidays and decided to build walls in your spare time or are you a structural engineer?

"They sag a little"
Yes that is the better wording I was looking for, rather than moving down a few mm. I couldn't grasp the concept that a little sag is "ok", but are you then confirming that a lilttle sag will not create cracks on the internal walls as if there were subsidence?

You said that walls are somewhat flexible. What is the tolerance level in mm approx for a wall to fall/rise due to ground swelling etc without it affecting structural integrity?

And yes, perhaps I did underestimate the strength of bricks and mortar! Thx again, never will I look at a Class B engineering brick at my DPC level again as I sit outside my patio watching my K-Render dry.

 

[tony1851]

You said that walls are somewhat flexible. What is the tolerance level in mm approx for a wall to fall/rise due to ground swelling etc without it affecting structural integrity?

Most of it has now been said, though here's my two penn'orth FWIW;

Masonry walls will be flexible - to an extent - because they are made up of small units, whether bricks, blocks, stones etc.

Much depends on the mortar. Modern cement mortars are relatively hard and unforgiving, so can tolerate only small movement before cracks develop.
Lime mortars are more plastic in nature and can accommodate larger movements before cracking.

It's rarely possible to give actual figures, but if you can barely see the cracks (even if they are all over the wall) it's nothing to worry about; if you can put your finger in a crack, maybe it needs looking at - at the very least it will let the rain in.
If you can get your hand in the crack, leave the building immediately.