How much does an extension cost?

[Effjay]

We are thinking about putting a two storey extension on the side of the house, knocking down existing garage. New upstairs bedroom and ensuite, with walk-in wardrobe, replace existing bathroom, and downstairs a new kitchen, laundry room and toilet. The current value of the house is c.£1m so needs to be reasonably high spec and I'm probably going to have an architect design it. In my head, I'm budgeting £100k - is this realistic? We're in Surrey.

Marking place as in a similar situation

I think you are underestimating the cost - you could spend £30k on a high spec kitchen alone and your build costs for a 2 storey extension will be more than £60k. VAT at 20% is a killer too.

I would allow £5,000 for drawings/structural engineers fees/build over applications/party wall agreements if all applicable

Then you should be able to bring the actual build in for £100,000 incl VAT with budget for kitchen and bathroom fittings on top of that.

You have not mentioned the size though.

Check the other thread about quotes. i think you would be talking double in the SE, as insane as that sounds.

Having just had quotes for an extension - I think if £100,000 is for the basic shell without including VAT or fittings / new kitchen / bathroom / perhaps bi-fold doors or whatever / flooring, then that might be do-able. If you're expecting to do the whole thing for £100k including VAT and all the extras (which is obviously only£80,000 plus VAT) then I'd say you're way off (sorry!). Even without going OTT on a kitchen / bathroom, you'd be looking at another £50,000 at least I'd say.

Ok, thanks, might need to postpone it for a few years to get a bit more cash together. Its looking like I'm under-estimating it - thanks for your comments though.

We had a single storey kitchen/diner extension last year plus some remodelling/taking out structural walls. Including kitchen, bifolds, utility, flooring, alcove units and furniture all to good spec, we spent £95k (in the south west).

Depends on the size, where you live and whether your local builders are in demand.

However, as a very very rough rule of thumb, try using £1500 per square metre of new building using the external wall measurements rather than the internal room size. So, for example, an 8m x 4m single story ext. would be around the £50k mark, 100k if it's two storey. That should get you the basic plastered shell with power, water and heating. You then add in the cost of supplying and fitting things like the kitchen, bathroom, flooring etc. together with any other non-standard things like funky bi-fold doors or unusual windows, under floor heating and so on...

That lot should give you a ball-park figure but don't forget things like architect, structural engineer and local authority fees - say 5% of the cost.

Think you need to double that tbh. £180 - 200k (going from friends experiences of the same). Also in Surrey.

We have been told £800 per m2 where we live (plus fittings) but we are in Shropshire and cheaper here I guess.

We're half way through a small extension to our kitchen, reorganisation of the interior to create a shower room and utility room. It's costing around £65k all in, but no decorating. Kitchen is about 22 m square, so not huge.
That includes bifolds along the front of the kitchen.

Also in Surrey!

Just echoing others really.. More than 100k. We're in the NE and recently had a basic two storey side extension, two bedrooms upstairs, two rooms, wc and utility cupboard on the ground floor so almost no fixtures at all. End cost was circa 53k (plus extra for some additional maintenance that it was easier to do during the build). We got the cheapest builder we could be sure was going to do a solid job but by no means a high end one. In the SE and looking for a high end finish I would be looking at doubling your budget too.

For what it's worth, we live in East Dulwich and want to do a wrap around kitchen extension, re jig of utility, under stairs loo, and bit of shelving for an office area. Our three quotes range from 167-190k inc vat, excluding glass, sliding doors and kitchen. That's on top of the best part of £20k to get planning, structural engineer drawings etc. We're a big flabbergasted.

I wrote this last September:

"The rough guide of 1,500psm is probably fair outside London however so much of a kitchen is variable - one could spend 5,000 or 15,000 on kitchen units alone. I assume by your dimensions it is to be a flat-roofed 'box' across the back of your house?

In the last 2 years I have designed 8 of these, all approximately similar areas to yours and all bar one attached to modern(ish) 'estate' type houses. Costs varied from 18,000 to 43,000.

Cornwall prices, local and well regarded small building contractors who supplied all materials and employed sub-contractors.

The 'other' one was to a 16 century cottage and was completed for a very reasonable 72,000! "

Since then there has been quite a rise in building costs especially in areas of high demand like the south east of England so I agree with other contributors that £100,000 is on the low side...