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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Building Questions >> Foundations for single story extension https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1384101783 Message started by mickanddenise on Nov 10^th, 2013, 4:43pm

Title: Foundations for single story extension
Post by mickanddenise on Nov 10^th, 2013, 4:43pm

I am building a single story extension to the rear of my house and while digging the trenches for the foundations I have hit solid ground that the digger will not go through. I am only down 1 and a half foot from ground level and two feet from floor level this will only allow about 300mm-400mm of concrete will this be ok or do I need to go at it with a pick axe.

Title: Re: Foundations for single story extension
Post by CWatters on Nov 10^th, 2013, 10:20pm

Building Regs Approved Document A Bottom of page 35..

http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_A_2004.pdf

Suggests that strip founds should be min 0.45m to the bottom to avoid frost unless on clay when it's 0.75m

The minimum thickness of concrete is detailed in Diagram 23. It depends on the width. eg The thickness T should be greater than P in the diagram.

Probably ok but the BCO will normally want to see the trenches before you fill them and he may have other ideas.