Where do you even start with an extension?!

[IToldYouIWasFreaky]

I want to look into having an extension. I have a three bed semi with a tiny kitchen and conservatory that goes across the back of the house. The conservatory is quite old and has the usual problem of being freezing in the winter and boiling in the summer so it's not really a usable living space.

My ideal solution would be to extend into the current footprint of the conservatory to create a large kitchen diner. Actually the really ideal solution would be to do a two story extension so we could have an extra bedroom and bathroom upstairs but I don't think we'd get planning permission for that.

However, I am so confused about where to start! I have spoken briefly to my mortgage advisor, to see what we can afford, but he really needs to know what we want to borrow. And I've also spoken to a project management person, but he wanted to know what our budget was. And I have no idea how much extensions cost! The situation is also a further complicated by the fact that currently the mortgage is in my name only. DP owns another house outright which he currently lets. So we can either re-mortgage in my sole name, add DP to my mortgage, sell his house to fund the extension, etc etc.

So yeah, where do you start when you want an extension? Do I need to get plans drawn up first?

Industry standard is about £2k/ new build, so if you are adding a 3m by 4m extension then START at £24k, which is shell only and doesn't include making good the floor or new electrics or whatever you are putting there (like new kitchen). There's drainage and fees to consider too (planning, structural engineer, building control, party wall agreement and so on)
Renovation magazine has some sort of calculation thing to help.

About £70K before you put in a new kitchen. But all the above you'd need to factor in too as maofteens says.

We got a builder we'd used before to come round and do a really rough quote for mortgage purposes. Also an architectural technician we'd used before. This was 2 years ago before building went mad and people became unobtainable.

The architectural technician gave us a rough idea of costs too so we drew up a pretty detailed budget for ourselves. When the tenders came in they were pretty much in that range.

I've read the a 2-story extension is cheaper pre sq m but for a single story i would budget at least 50k before kitchen.

Not sure how anyone can give you a figure without knowing the size of the extension .

I think the £2k per sq/m has actually moved on now, I'd be surprised if you can get an estimate for that but it does depend on where you live. I'd work on the basis of £2.5k per square metre, plus VAT. If you're thinking of double storey, then the square metres will double.

You then need to think of the extras - most quotes will include the basics such as windows / doors, electrics and plumbing that you'll need (i.e. the services that go behind the walls) and then a plastered finish. You'll need to add on flooring / decoration / kitchen (and fitting), lighting and then anything you want to upgrade (e.g. chrome plug sockets instead of white ones, nicer radiators, nicer internal doors etc).

Once you've got that figure, add on about £5k for fees / planning permission, and then approach the lender / broker to see how you finance that.

Then its a question of deciding if you want to go ahead - get drawings prepared and submitted. If you go on your council's website, you can see what houses in your road have applied for and usually on the drawings, they have the name of the architect that has prepared the drawings. You can contact them to see if they think you'll get planning / what their costs are etc.

Oops I'd read a size somewhere...

Most planning departments are surprisingly helpful if you wanted to ring them and ask about possibilities for a 2 storey extension.

Oh and add in some for reinstating the garden - ours got totally wrecked.

Thank you - there are some great tips here! I especially like @Africa2go suggestion of looking for the architect by viewing drawings - I had no idea that was possible.

Good point about the garden. It's in dire need of a full overhaul, and we've got a huge shed to remove which will to come through the house so that needs to happen before any renovations.

If you're not going beyond the existing footprint (and not the 2 storey) it will be much less than what some are quoting above. We did exactly this converted existing conservatory into part of the kitchen-dining-room.

Ours was under £35k all inclusive. Feel free to PM me if you want some information as it sounds like a similar project.

Does the fact there is an existing conservatory mean some groundwork is down already, or does that not really make a difference? I too had though would be more around £35000 so am horrified at the thought of £70! I could not spend £70 on the house and ever expect to make it back due to ceiling price in the area.
Some prices must vary considerably depending on where in the U.K. etc? (Clutching at straws here!)
But I'm still unsure, like the OP, who you start with - architect and drawings? Builder?

My architect gave me loads of advice before I committed so maybe start there with some enquiries?