4m Small Extension

Question

We are doing a small extension (4m2) and wondered if you can guide us on depth of footings necessary for a single storey extension, with flat roof, on a concrete slab. There are two perpendicular walls to build as it joins the main house. And would you suggest an expansion strip at the wall joint or Key in to existing brickwork? Thankyou for your help.

Lewis · Accepted Answer

Are you using building control? Because usually they decide on the depth of footings depending on what the ground is like, but usually it’s around 1m deep but could be deeper if there’s trees etc. You can furfix the new brickwork against the old or tooth it out, but again usually building control would tell you what they prefer but if your not using them you could do either

Wesley · Answer

"The depth depends on what the ground is like you have to dig to solid ground. For a single storey building strip foundations will typically be 450mm wide and at least 200mm deep, and for two storeys 600mm wide and 200mm deep.

Ali · Answer

30cm width
1.5m depth
May require reinforcements

Matous · Answer

Hi there you are looking around £12,000 with the material.

Steven · Answer

In clay.  1 metre deep x 600mm wide.  
On sand 750mm deep x 600mm wide   But dependant if trees are within 5 meters of the build. 
Building are unlikely to allow toothing in but use a firfix/crocodile ties to attach the brickwork/blockwork to the existing house.

Charlie · Answer

Generally, the required depth of a footing for an extension is a minimum of 1 meter deep depending on the ground you are on. Sandy ground or clay 1m is fine.

Aurel · Answer

The footings for an extension are usually 1m deep and 60 cm wide.

Jason · Answer

The depth is determined by the ground conditions and building control, they would normally want you to go as deep as the original house footing and as said depending on the conditions maybe deeper, as regards the walls just use the wall tie starter kits, their really good and perfectly acceptable

Amos · Answer

Firfix against existing property foundation same level as existing property thanks.

Tom · Answer

You do have to go down 1 Meter for a curtain for a porch or a extension with either a flat roof or a pitched roof and if you do need any more help their contact Greenacres landscape and general building

4m Small Extension

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