DIY timber framed extension

[Mallowmarshmallow]

We are looking to build an approx 3x3 extension on top of a ground floor extension we had built a few years ago.

It would be timber framed, clad and flat roofed. We're in a chalet style house so some eves would need to be knocked out.

It would enable us to have and upstairs shower room and increase the size of the smallest bedroom.

My brother is fairly convinced he can build it. He's a tradesman (not a builder) but generally handy, as is my husband. We would use trades for electrics/roofing and plastering.

Has anyone done similar themselves?

I'd want to check it's possible to do first. Can it comply with building regs and will the foundations take another floor. There are companies that do timber frame extensions , is the rest of the house timber frame ?

Yes, we would get plans professionally drawn up and require building consent first as it's second flooring. The precedent on the street suggests it shouldn't be a problem to get consent.

Our downstairs was built when regulations dictated foundations must be sufficient for a second floor to be built on top.

When you built the ground floor extension previously, did you build the foundations deep enough to support two floors? Our local authority inisist on that now, so you may have done already, but that's a good starting point.

Would your brother know and be able to comply with the necessary building regs?

Would your mortgage company have any stipulations around a timber frame extension?

I'd personally be very wary of a flat roof, they often leak. I'd want a company with a guarantee to install it in case anything goes wrong.

This should be very achievable if done methodically and safely. Please make sure that proper edge protection is used when working at height! Sadly there are far too many accidents on small construction sites. A flat roof should be fine' again if installed properly - but a pitched roof might look better?