House Extension - extra costs please

[mynameischloe]

We are planning a single story extension, currently early stages.

We are obtaining quotes for the work and I am making a list of all the extra costs we need to consider outside of the building work. So far I have:

Flooring costs (also would need to re-floor the old part of the house to match the new)
Decorating
Blinds/curtains
New dining table and chairs
Small sofa and new TV for small sitting area
Radiators/heating
Any new interior doors

What am I missing please? DH thinks we can stretch to a larger extension... but I want to show him how much everything else will cost which will push us out of budget.

Plus a contingency of 10% and then some more!

Thank you.

On a practical note, there are some ways to keep the cost down. In our case, we have the most structurally simple extension possible and didn’t need steels. We also went for standard white PVC doors and windows. I would definitely say if you can keep it simple, that can make life easier.

Also, the more you can plan out at an early stage, the more accurate your quote will be. We had all the electrics set out on our building control drawings and maybe added in one socket. Really think about electrics and plumbing early on - changing them halfway through is expensive.