Foundation question????

[Multibez]

At the rear of our house we have a single storey cavity wall extension. 1.5m x 4m with a flat felt roof. We're intending on keeping this but glazing the roof and putting in some bifold doors. All good...........

I've had a SE do some calcs so that we can remove some further internal walls by installing some steelwork.

Some of this new steelwork is going to span across the existing single storey,sat where the roof used to be and pushed up snug to house.... hope your still with me??

Building control are now saying they have concern for the single storey foundations (after looking at drawings) and want me to expose them as they are going to be under more load with new steel sat on them, still all good I can understand this.

On exposure of foundations I've got 4 bricks deep under DPC stepping out at bottom by two half bricks onto clay.

Where the padstone are to sit, the bricks underneath have been toothed back into inner leaf of existing brickwork of house so partially spreading load.


In short will this be ok!!!!!

hope this makes sense

Cheers

 

[pilsbury]

How old is this extension? Sounds like you have a brick footing foundation. I have that on my original 1925 house. Building my new extension required 1m of concrete trench fill foundations. Think it’s been this way for donkeys years.

 

[^woody^]

If the BCO does not think it adequate, then your engineer will have to prove otherwise or come up with something.

 

[Notch7]

Are you saying there is no concrete foundation below the brick spread footing?

That wont be any good. If there is concrete, you will need to dig to the bottom.

Under building regs the brickwork shouldnt be returned and join the inner leaf. I expect you will have either cut a slot for a vertical dpc, or open the cavity and fit a cavity closure

 

[Multibez]

Are you saying there is no concrete foundation below the brick spread footing?

That wont be any good. If there is concrete, you will need to dig to the bottom.

Under building regs the brickwork shouldnt be returned and join the inner leaf. I expect you will have either cut a slot for a vertical dpc, or open the cavity and fit a cavity closure

nope no concrete, just brick onto clay, but bricks spreading out as they come down.

sorry prob not explained myself well enough, ive maintained the cavity and returned into inner leaf of house the padstone will obviously be sat on inner leaf

 

[Multibez]

How old is this extension? Sounds like you have a brick footing foundation. I have that on my original 1925 house. Building my new extension required 1m of concrete trench fill foundations. Think it’s been this way for donkeys years.

yeah mine is circa 1925 and my foundations are like this, im starting to wonder whether this "extension" wasnt actually an extension and actually part of the original house as foundations are the same.

 

[Notch7]

nope no concrete, just brick onto clay, but bricks spreading out as they come down.

sorry prob not explained myself well enough, ive maintained the cavity and returned into inner leaf of house the padstone will obviously be sat on inner leaf

I expect you will have to underpin. From memory, it means digging out a a section, a metre down then fill with concrete. When set the gap is hard packed with dry concrete. It needs specifying by a structural engineer. Its a pain, but doable unless your ground is carp, and/or have trees nearby.

Lets hope your house foundations are better or you will have the same issue, if your are widening the opening there too.

 

[Multibez]

I expect you will have to underpin. From memory, it means digging out a a section, a metre down then fill with concrete. When set the gap is hard packed with dry concrete. It needs specifying by a structural engineer. Its a pain, but doable unless your ground is carp, and/or have trees nearby.

Lets hope your house foundations are better or you will have the same issue, if your are widening the opening there too.

is underpinning actually going under current foundations, or is it kind of in parrallell to existing

cheers

 

[Notch7]

is underpinning actually going under current foundations, or is it kind of in parrallell to existing

cheers

Underneath. I dont know if a pad at each end is ok with a big opening, or the whole way along.

If its whole length, its done hit and miss, otherwise the walls gonna collapse.

Probably no need to do whole length as you arent supporting anything other than a door cill.

 

[pilsbury]

Unless the extension was done an absolute age ago right near when the house was built, it may well be original house.

 

[Notch7]

Unless the extension was done an absolute age ago right near when the house was built, it may well be original house.

Yes thats certainly possible. I cant think any extension would have been built without foundations. Mind you a flat roof seems unlikely.

 

[John D v2.0]

Ours house is the same age also no foundations and originally the SE said build new piers, but when the architect asked for a new design the SE decided on the existing walls was fine with a big padstone.
This is for a 3m long UC supporting the old upstairs rear wall and back of the roof.
He said the extra load would be relatively small by the time it was spread out.
So based on that you'll be fine!