most cost effective and highest performance method of building an extension

[magicnumber7]

Expert or non-expert views welcome!

Being in the midst of building an extension on our house, I'm perhaps naturally thinking about how I would do it differently next time. Particularly about how to get the best bang for your buck on the build.

The current extension is pretty standard 300mm cavity walls with rendered block on the inside leaf and a mix of rendered block and facing bricks on the outside, cavity has 100mm thermal Rockwool. Trench fill foundations 600 wide and 1100 deep. Steel everywhere (it's a wrap around extension). All fine, but just more expensive than I think it could be.

Anyways, your advice in thinking about the next job is welcome

 

[johnny2007]

Was the steel to structural engineer spec or the architect just threw it in?
In the years I found out that many times you don't need steel, but it seems to have become popular amongst designers.

 

[Ian H]

I don’t like open plan so guess that would make any structural alterations cheaper.

 

[^woody^]

Use a different designer next time

 

[23vc]

Do you have a breakdown of costs? I doubt there’s a fundamentally much cheaper version of the construction techniques you describe otherwise everyone wouldn’t be doing it