Double storey extension

[HahaHarrie]

How much would it roughly cost to do a double storey extension of 3m x 8.2m (10ft x 27ft)? I am in Surrey - London border.

Also how long does the build take?

Many thanks

Almost impossible to guestimate as so many variables, but we had something similar done in a comparable area and cost in the region of £150k.

It took about 8 months in total, but then it was a reasonably complicated extension. Hope that helps.

150K?!!! That sounds insane to me. I would be thinking more around the 70k mark.

1,500 psm on the ground floor and 1,200 psmfor the first floor. That's just for the building work roughly. What are you putting in there? If its a kitchen extension, you'll need to add flooring, kitchen etc. Also, that's for a pretty basic spec, if you want underfloor heating or bifold doors etc, it will be more. Unless you extension is very small it will probably be more than 70k, especially once you add in design fees, engineering drawings, planning etc.

About £50k for the basic build, plus costs for any finishing (painting, carpets, kitchen/bathroom etc). Although it depends how much of a hurry you're in - decent builders are booked up well in advance and will give a high quote if you want it done soon.

Blimey. We paid £30k in North Lincs for one large room downstairs with folding/sliding doors the full length of one wall and a bedroom and bathroom upstairs plus the whole extension and the old house being re-roofed.

Thanks everyone, that's very helpful. I'm thinking about a ground floor extension the length of the back of the house. Increasing the size of the kitchen and living space. Tempted to do the second storey at the same time (funds permitting), to enlarge two bedrooms, the bathroom and add an ensuite. It's not a massive extension but it all adds up. DH might take some persuading too.

We did something a bit bigger in London (zone 4) for about £80k not including fit out. Ours was side and rear though, 9m by 9m by 3m deep round the outside of the house.

It has taken eight months. So far.

8 months! That's a long time - or maybe not, that's just how long it takes. Did you move out for the renovation? Our is a new house purchase so we'll continue renting until it's time to move in. I'd rather not be paying rent for 8 further months but might have to factor that in to the costs.

We had similar done about 10yrs ago , cost about £90k for everything new kitchen, flooring to whole of downstairs and 3 bedrooms upstairs etc etc. In Hants.
It took approx 10 weeks and we moved out for 5 of them I think.

included new windows to whole house as well

By coincidence I wrote this on another thread (about design fees) over the weekend:

"Some recent single storey flat roofed extensions I have designed have worked out at between 800 and 1800 per square metre - basic build cost - (sorry pound sign not working on laptop!!). Cheapest rate was rendered blockwork on ex-council house, top rate for stone and sloping site on listed building. South West rates."

"My fees (architect) ranged from 650 to 2000 for survey, sketches, advice; and production of the building regs application drawing, which contains existing and proposed plans, elevations, site plan, location plan, basic section and notes."

"A builder could use this type of drawing to prepare an estimate but a full tender package including a specification would cost another 600 - 1000 or so."

The second storey would typically cost around 50-70% of the ground floor rate depending on the roof type.

Add another 30-50% to the lot for being in the south east of England (my rates based on west country).

Time? If you mean just the construction then you are vey much at large to an extent because it all depends on the builder and the local market however I would be unhappy if I was supervising a project of that size which took longer than 4-5 months.

If you mean the whole project from initial chat with the architect to handover (and cracking the champagne) then allow an extra 3-6 months depending upon if planning consent is required.

Hope this helps and best of luck.

Yeah, don't try and do foundations or block work in the wettest winter in recent years. That will hold you up a bit...

We had plans drawn up in December 2012, planning permission applied for in May 2013, started the loft conversion in July and the extension in September, so I suppose it didn't take all that long. We moved out for two weeks. Builders would have liked to have us out for much longer, and it would have been quicker, but just not possible for us. And frankly they needed a fair amount of supervision from me, or really stupid things happened. Like a sink right in front of the door. Or radiators taken off and water spewing into the room below.