Padstone on outer wall

[Geo57]

Hi

In situations where a side extension is being built, I have seen a number of plans where the padstone appears to sit on the external wall of the existing house (and then the other end of the steel sits supported on the new internal skin at the other end)

In these scenarios, is the fact that the padstone is allowed to be built into the external wall (rather than the load bearing internal wall) as a result of SE calculations to show that the existing foundations are satisfactory? or are other factors used to determine that this is satisfactory?

Cheers
G

 

[stevie888]

In a typical house the outer skin is brick so stronger than the inner skin, usually lightweight block. Both sit on same foundation.

So the answer to your question is yes. FWIW we rarely consider the foundations at all unless we're dealing with proper big steels.

 

[noseall]

Hi

In situations where a side extension is being built, I have seen a number of plans where the padstone appears to sit on the external wall of the existing house (and then the other end of the steel sits supported on the new internal skin at the other end)

In these scenarios, is the fact that the padstone is allowed to be built into the external wall (rather than the load bearing internal wall) as a result of SE calculations to show that the existing foundations are satisfactory? or are other factors used to determine that this is satisfactory?

Cheers
G

Both walls sit on the same foundations. The only difference being load wise, is the brick outer skin often possesses a better crushing/impact strength than the inner blockwork. Seems like an odd concept considering the inner leaf carries the greater load. In wholly block built rendered structures of course, the issue is moot.

 

[Geo57]

Thanks both, replies much appreciated and makes sense now!

Yes my outer skin is brick and steel will be around 4.3m long, so the pad stone sitting on the external wall makes sense


One final question, will it be the SE who also designs the load bearing pillars for the other end of the steel to sit on?
(From initial research looks like these would be built on pad foundations, but are these columns generally built out of engineering bricks for instance)

Just trying getting my head around things before I find a SE to calculate all this.

Cheers
G

 

[alex.bennett]

That decision comes from the engineer, not just a rule of thumb. They check the load path, wall type, and foundation size to see if the existing external wall can take it. If it can’t, they’ll usually call for a spreader plate, a pier, or a post down to new footing.