4m Small Extension

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.

Asked by Tracy on 7th Jul 2021
Expert Trade Answers
"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"
Answered on 7th Jul 2021 - Member since Nov 2020 - report
""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."
Answered on 7th Jul 2021 - Member since Jun 2021 - report
"30cm width
1.5m depth
May require reinforcements"
Answered on 7th Jul 2021 - Member since Feb 2020 - report
"Hi there you are looking around £12,000 with the material."
Answered on 7th Jul 2021 - Member since Dec 2019 - report
"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."
Answered on 7th Jul 2021 - Member since Nov 2017 - report
"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."
Answered on 23rd Aug 2021 - Member since Aug 2021 - report
"The footings for an extension are usually 1m deep and 60 cm wide."
Answered on 4th Aug 2021 - Member since Mar 2020 - report
"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"
Answered on 20th Jul 2021 - Member since Sep 2020 - report
"Firfix against existing property foundation same level as existing property thanks."
Answered on 9th Jul 2021 - Member since Jul 2021 - report
"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"
Answered on 10th Jul 2021 - Member since Nov 2020 - report
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