Groundwork & Foundations Question

What is current minimum foundation depth for new build house

Current living in bungalow and and thinking of knocking bungalow down and building two storey house on same foot print as bungalow using existing foundations.
Current depth of foundation is 600 mm with 250 mm concrete.
I have been told modern standard is 900 mm
Trying to establish if I can build on these existing foundations

6 Answers

Best Answer

Footings need to be minimum 1m deep by 600mm wide.
We always trench fill with concrete.
Final decision will be with building control, hope you dont have any large trees near.
We just completed a job, 1m footings as spec, building control noticed a Holm Oak tree about 30m away, made us go down 3m and fit clay boards, lots of extra expense, ie trench sides collasping, more concrete.
A lot depends how lenient the inspector is, the young ones seem more keen.

Answered 10th Mar 2011


Member since 29 Oct 2008

Hi Kevin.

For a new build house the foundation depth is dependant on ground conditions, soil type and proximity of trees etc.
If the new building is going to be built on a demolition sites or has unstable ground conditions on the plot then piled foundations maybe required.
An architect (or similair) should summit plans to the local Building Control officers', proposing what type of foundations and how deep they will be. Unless they are being built under a NHBC scheme or similar.
It is upto the Building Control Officer or independant surveyor (NHBC etc) to be satisfied that the foundations when dug, but not filled, are satisfactory.
Foundations sometimes have to be made deeper/wider than the planned amount.
There is no min and max depth. Trenches do not need completely filling with concrete.
All exisiting foundations need removing anyway for a new build.

Hope this helps and dispells some urban myths.


Answered 12th Mar 2011

Dream Makers

Member since 6 Jan 2011

No feedback

Your existing footing is not substantial enough.Footings need to be 600mm wide x 1m deep minimum,in some cases depending on ground quality/type,proximity of large trees footings are required to be up to 2m deep.For good impartial advice speak to your local building control office,hope this helps.

Answered 10th Mar 2011

m w building construction and property maintenance

Member since 28 Sep 2008

speak with building control they have the say on that one.

Answered 11th Mar 2011

y,not build

Member since 3 Oct 2009

This is a question which will have every answer possible. Fact is your Architect/building control/structural engr will decide this one.
In my experience building control will be reluctant to remove the old footing as this will disturb a lot of earth.
Kind regards.
NR Building Services.

Answered 11th Mar 2011

NR Building Services

Member since 19 Nov 2009

The depth of the footing is ground dependant. The only way to find out the depth is to consult building control who will advise you correctly at the time of digging the foundations. Most building companies will allow a price for 600mm wide x 1000mm deep but footings do NOT need to be 600mm wide or 1 mtr deep as somebody else has mentioned. This is a new building you are constructing so the old building has to be completely removed, including all foundation and old drainage so that is your starting depth.

Answered 10th Mar 2011

ibuild building services

Member since 28 Jun 2008

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