Footings question

[nathanrobo]

Hi

I have a 12 year old detached house that my neighbours tell me has piled foundations.

I've bought a conservatory (4.2 x 4 mtrs) and wanted to dig decent footings for my dwarf wall so that at some point in the future I would have the option of replacing the conservatory with an extension.

I've started my trench and found that the ground was made up with plenty of builder rubble down to about 1 metre. So I kept on digging until I got to firm clay which is at between 1.2 mtr and 1.4 mtr depth. I was planning to apply for building control (even though conservatories are exempt) so that I could get the footings documented. Question is... given that the rest of the house seems to be on piles will the inspector accept foundations of 1.4mtrs deep for an extension if I've hit good firm clay?

Any advice... I am planning to tie my new foundations in with the house foundations using steel rods and to use steel reinforcing in the trench.

Thanks guys

 

[leew2]

Are there any trees nearby?

 

[nathanrobo]

No trees, just a few plants with shallow roots.

 

[ickythebricky]

hi as iv seen youve dug at a depth of 1.2, i cant see there being a problem, even though youve hit clay ( water sits on this) most building authorities/inspectors like 1m deep and 500mm wide. you may get an alkward inspecter that may ask you to go deeper or wider to spread the foundation, but im sure youll be ok.

 

[^woody^]

Why have you posted this again?

Anyway, foundations are never tied in to existing ... unless its underpinning in bays

And trench reinforcement wont do anything

 

[nathanrobo]

Thanks for the clarification Woody. Apologies for the double post, but I originally posted under general building (I think), then found building regs and thought it would be more appropriate.

I'm new to the forum so still finding my way around and trying to gauge how many posts to expect. Eg on other forums I use like the landcruiser forum, you tend to get lots of responses very quickly and then it goes dead.

btw still trying to understand if building control will allow an extension built on ordinary footings on firm clay ground if it goes onto a house that has piled footings.

 

[amwc]

There is obviously a reason that the house was piled as this an expensive option to go down. I'd be careful that you have not just hit a shallow seam of firm clay that is sat on something less substantial.

 

[nathanrobo]

Good to know! Probably worth taking a soil core sample?? Anyone know who / how to get this done?