Starting planning a 2 storey extension

[FlossieFrog]

We want to extend our house with a 2 storey side extension. Basically it means demolishing the existing detached garage and then building the extension to include garage and living room on the ground floor and two bedrooms and bathrooms above. I'm trying to work out roughly how much it will cost before we embark on finding architects etc. So, does anybody have any tips on budgeting? Has anyone done similar and can tell me how much theirs cost? Should I just start finding architects and ask them?

FWIW we're in East Sussex.

We did very similar. Demolished garage at side,built extension which was 16 feet longer than side of house (goes out front and back), also had the front area filled in to create a new hall. The extension is an integral garage, kitchen and utility downstairs, master bedroom, dressing room and en suite above. In addition we had a lot of work done in the existing house, new boiler, windows, doors, chimney removed, etc etc. It is probably more work than you are doing, but we didn't have much change from 150k. As a rule of thumb, you can work it out for yourself at approx 2 to 2.5k a square metre. Our build time was six months. Hope this helps.

@Lucisky that's really helpful, thanks. I've looked at the £2000/sq m calcs and seem to be coming out at £200k, which seems ridiculous. Ideally I'd like to build it for £100k. Did your £150k spend include everything - VAT, all fees etc?

Yes, everything, Inc. VAT (that was a lot!),plans drawn (no architect as I designed it myself), planning, building regs, the lot. For that we have got our lovely extension, refurb of existing house, new drive, new patio, so quite a lot of extras. We saved money by going for a simple spec and mid range fittings. The builder we used gave us a fixed price for the project, oversaw the whole thing, so it was pretty stress free, but I had to wait over a year for a build slot as he is very popular and busy. If you know what you want it is easy to design it yourself, and then get the drawings done. Things like electrics I didn't actually position until we got to first fix, and then we just went round with the electrician saying where we wanted lights and sockets. It is easy to get too bogged down in small details before you have to. As long as you know where any steels may be needed, and where you want windows and doors and internal walls, everything else can be decided as you go. Have a go at drawing it yourself and see how ithe design works for you. Good luck.

Just to add, the cost does depend where you live. We are in the south west, and it actually worked out at about 1.5k a square metre, but this was costed up two years ago now, I think if you are south east or London it is more, and everyone seems to say 2k per square metre minimum now. Don't stint on the build cost, but you can save money on fittings, and a good builder will always try and get good deals for you.