Structural engineer for foundation design only cost

[KayleyH]

Hello, we are doing a 48m sq extension.  We have the architects drawings and the oak frame company we are using are providing the frame structural drawing etc but not the design for the foundations.  Has anyone used a structural engineer just for their foundations and what was the cost?  Many thanks.

[jayc89]

Our SE has no interest in our house foundations. He is designing our garage foundations as it's so close to a tree, he's quoted £500+VAT for that

[George]

Unless you have ground investigation information, it can only be a specification based on informed guesswork, not a 'design' as such.

 

For a that best guess for traditional foundations (concrete strip or trench) I'd maybe charge a few hundred pounds - basically looking at what information is available on the British Geological Society, maps and borehole data, specify minimum width and depth of the foundation based on provided loadings and any tree influence zone. (edit - plus reinforcement design for pads etc)

 

Because traditional foundations are specifically covered in the Building Regulations, the main person will ultimately be the Building Control officer. They are able to instruct wider or deeper foundations within the limits of the Building Regulations. Thankfully they should also have local knowledge of the ground. (edit - but they won't do the foundation set out for you especially with an oak frame with point loads to consider)

 

They might say traditional foundations are unlikely to work. Then other common options for domestic construction are rafts or piles.  For a relatively straightforward reinforced concrete raft foundation, I'd be looking at best part of a thousand pounds, mainly because the drawing work is more intensive. 

 

If it's pile foundations then you are best going direct to a specialist contractor who can do the design and install.

 

 

Edited July 28, 2022 by George

[TonyT]

60m2 extension 

 

£900 included two sites visits after trial holes were dug also included drainage design. NE Fife

front of extension was 2.4 m concrete deep

[KayleyH]

Thats great, thank you.