Can I utilise existing foundations & wall detail?

[Phil D]

Hi All,

 

Bit of a general question regarding foundations, would be great of anyone can point me in the right direction.

 

I’m looking at a house with a view to extending & refurbishing, it’s a 1970’s bungalow with large dormer windows within roof/1^st floor level. My basic intention is to retain everything from the ground to first floor finished level and build up the wall to create a proper 1^st floor area (currently a dormer window config with the roof sitting onto of wall finished at FFL).

 

What’s the general approach when looking at foundations, I’m guessing I’ll have to expose existing and assess their loading capacity to take proposed 1^st floor wall loading and new roof. Is it a simple case of reinforcing existing foundations?

 

Any general pointers would be much appreciated with the above scenario? Risks, expense etc? Am I looking at this correctly?   

 

Thanks,

 

Phil

[Ferdinand]

You will need proof that they are adequate, which would be a surveyors report plus probably digging test pits to demonstrate it to the BSO.

 

If you are having a pre-pack Timber FRame 1st storey added that should perhaps come as part of the feasibility study / assessment.

 

Ferdinand

 

[Phil D]

Hi Ferdinand,

 

Yeah, thought so. We're waiting to hear back regarding our offer so little we can actually do at this stage. 

 

Some other forum members have kindly pointed out the VAT savings on a new build which may actually make it easier to demo and start from scratch.

 

Is anyone familiar with the actual construction method for reinforcing foundations? Just for my own curiosity really, presume you would have to dig alongside existing and dowel into? I guess you could only do this if the existing are set at the right depth for fear of undermining them?

 

Its probably an impossible question to answer given all the variables with soil type, loadings etc to factor in.

 

Thanks,

 

Phil 

 

[ProDave]

You normally dig alongside the existing foundation and down until you just find the bottom of the concrete.

[Gone West]

3 hours ago, Phil D said:

Is anyone familiar with the actual construction method for reinforcing foundations? Just for my own curiosity really, presume you would have to dig alongside existing and dowel into? I guess you could only do this if the existing are set at the right depth for fear of undermining them?

 

 

Usually involves underpinning the existing foundations. Can be done by digging out alternate 1m long sections under the foundations and filling with concrete. When set the intermediate ones are dug out and filled. The depth depends on what is already there.

[Ferdinand]

Doesn't @Construction Channel have a video about DIY underpinning?

 

Edit: (Which is only an illustrative demonstration of the sort of work that you might want to do to reinforce your foundations were you completely mad and doing it yourself).

Edited August 21, 2017 by Ferdinand
For a**e covering purposes.

[Phil D]

Most helpful, cheers fellas.

 

I'll have a look at construction channel shortly.

[Construction Channel]

1 hour ago, Ferdinand said:

Doesn't @Construction Channel have a video about DIY underpinning?

 

Woah there! those videos are for entertainment purposes only!! especially the underpinning ones.  as stated in my infallible disclaimer 

 

but if you wanted to watch them purely for that reason.... here you go  (this should start the playlist)

 

 

christ that was a long time ago......

[Gone West]

A friend underpinned an 18th C. barn he was converting back in the 90s using the method I mentioned above. It didn't have any foundations to start with just a very thick brick plinth wall. It was hard work digging out cubic metres of earth but worked very well.