Guide to house extension costs

[tillson]

Don't forget the DIY and Home Improvement Deals Note

I am in the process of planning a ground level extension to my house 3.5 metres x 4 metres apex roof. Is there a rule of thumbe for estimating building costs? For example £/square metre formula.

I just want to have an idea of roughly where the prospective builders should be giving their quotes.

Thanks

Tom

[BobProperty]

Very roughly £1000/m2

[Eyesparky]

I think it would be worth you buying a copy of "The House Builders Bible" by Mark Brinkley http://www.amazon.co.uk/Housebuilder...309066-0616635

This is a really helpful starting place for any building project or renovation, giving an indication of material and labour costs for most projects (or a guide where to find out current costs). Hope this helps.

[shelly]

We had an extension built last year, slightly larger than yours is going to be, ours was 4m x 5m. It cost £11K all in.
That was project managing ourselves, hubby done alot of labouring...i.e clearing site, digging footings and moving materials from front of house to the rear. Also he did the wiring and plumbing himself. The planning app and building regs cost £500 but vary depending on size of proposed extension. We also sourced ALL the materials ourselves as the builder wanted too much to supply and fit, so we supplied and he fit. Its worth getting a quote for both though.
Definately worth having the tiled apex roof, the difference between this and a flat roof was only about £300 and it looks way better IMO.

Last thing you MUST remember to do is to get a completion certificate from the building inspector. You will need this if you ever sell the property.


Anything else you want to ask please feel free to do so, either on this thread or by PM.

[babyangel10]

Have a nosey at this site too - it's not bad for getting an idea of costings and other things: http://www.house-extension.co.uk

[Gareth Davies]

I live on Anglesey, which is hardly the most expensive place in Britain to live, but when I asked an architect for an estimate of how much the building costs would be to extend our bedroom out over an existing single-storey extension (basically sticking three walls on top of three existing ones and putting a roof on), he came up with £24,500+VAT, and the available space is only 4mx4m.

This sum doesn't include fees for anything else (architect, planning etc.).

From what I've been able to pick up of the Web, this is grossly overpriced, but should I bother getting a second opinion? I could only really even consider going ahead if the price was about half what the architect estimated.

Regards

Gareth

[never enough]

Originally Posted by Gareth Davies

I live on Anglesey, which is hardly the most expensive place in Britain to live, but when I asked an architect for an estimate of how much the building costs would be to extend our bedroom out over an existing single-storey extension (basically sticking three walls on top of three existing ones and putting a roof on), he came up with £24,500+VAT, and the available space is only 4mx4m.

This sum doesn't include fees for anything else (architect, planning etc.).

From what I've been able to pick up of the Web, this is grossly overpriced, but should I bother getting a second opinion? I could only really even consider going ahead if the price was about half what the architect estimated.

Regards

Gareth

Do get more quotes. I had an architect around & we discussed various figures that were so far outside anything sane that I've forgotten them!
Think it was £130K!!! I am after a large double extension, but that's a crazy price, you can build a new house for £60K!!!
Is the current structure suitable to build on, or will it need to be knocked down & rebuilt?

[Gareth Davies]

Sorry - I didn't realise my post had been replied to - I'll look for an option that emails me in future when that happens.

The current structure is fine to build on - in fact it's identical to one on the same side of the house on which we had built, with no problems, an extra bedroom 25 years ago, and is a simple 4mx4m square (or 3 sides of one).

At that time, we had that work done - and a huge extension at the end of the building which exactly doubled the size of the house (which was already quite a big one) - all for £25K!

Our recent experience only underlined the effects of house-building inflation over the years.

Regards,

Gareth

Originally Posted by never enough

Is the current structure suitable to build on, or will it need to be knocked down & rebuilt?

[halia]

Originally Posted by shelly

We had an extension built last year, slightly larger than yours is going to be, ours was 4m x 5m. It cost £11K all in.
That was project managing ourselves, hubby done alot of labouring...i.e clearing site, digging footings and moving materials from front of house to the rear. Also he did the wiring and plumbing himself. The planning app and building regs cost £500 but vary depending on size of proposed extension. We also sourced ALL the materials ourselves as the builder wanted too much to supply and fit, so we supplied and he fit. Its worth getting a quote for both though.
Definately worth having the tiled apex roof, the difference between this and a flat roof was only about £300 and it looks way better IMO.

Last thing you MUST remember to do is to get a completion certificate from the building inspector. You will need this if you ever sell the property.


Anything else you want to ask please feel free to do so, either on this thread or by PM.

Shelly - can I PM you or ask your advice? We are thinking of a move into a lovely 2 bed end of terrace house. But to do so we need to build an extension to give us 3 bedrooms. My preferred option at the moment is to do a double storey extension at the rear of the house. Its an end of terrace so no party walls and good access down a side tenfoot. We need to extend by 4ftx9ft (or about 1.5mx3m)
Questions for you or anyone else:
rough costs of the 'shell building work' for 1.5mx3m double storey, includes taking down old end wall, 3 new windows and 1 new door?

We can do all the work of fitting bathroom/kitchen etc ourselves (have done this several times already) - but how easy is it to get builders to just do the shell?

That will give us a third single bedroom of 6x9ft, a family bathroom 6ft square and a larger kitchen 9ftx13ft. Do people really expect more than 1 bathroom in a terraced 3 bed house or is this just the influence of posh houses/new builds/americans?

We'd be left with a back yard 15ftx10ft narrowing to 6ftx14ft - very sunny and private does the loss of 1.5mx2m make a huge difference (its only 2m as we'd take down an existing brickbuilt outside loo)

Would this fit in permitted development rights?

Is there a price differential between 2bed and 3bed houses? (we're not doing it for profit but its nice to know)

Do we need an architect or can we/builder draw up the plans?

[tillson]

I have started to obtain quotations for the proposed kitchen extension and shower room to our house. I have had detailed plans drawn up by an architect and I have written a detailed specification quoting the finish and services to be provided.

It basically consists of gutting the existing kitchen (Approx 3 m x 5m) demolishing a conservatory (approx 3m x 2.5m) building a single storey pitched roof extension 3.5m x 4.2m (2.5 of the walls already exist), creating a toilet and wet room in half of the old existing kitchen (2.7m x 2 m). The build is to be completed as far as provision of all electrical, drainage and water services in a plastered shell with concrete floor all suitable for tiling or painting.
I have put the plans and spec out to four companies whose work I have seen and know to be of a good standard.

First quote is £35000.00

This does not include the provision of any decorative finishes such as tiles or flooring or the supply or fitting of the kitchen or the supply or fitting of toilet and shower room hardware. Also the wet room waterproofing / creation is not included.

This first quote is about £10K higher than I was expecting. Am I being over optimistic or is this builder trying it on? I am still waiting for the other three quotes to come in, but this first one is a bit of a shock.

[BobProperty]

Where about in the country are you? Home counties / London prices are going to be a lot more than say, rural Lancashire.
My initial reaction is that £35k is a bit OTT but getting it done for £25k is perhaps a bit optimistic. Rule of thumb extension cost is £15k. Also, what are the ground conditions like? Fylde coast is a lot more work than say Manchester (typically).
Sorry just re-read it. It does sound high and even £25k might be OTT. Depends a lot on location.

[Will_it_make_me_rich]

I suppose it depends on where you live as well.
Personally I think £35000 for a 14.7m2 extension is steep.
Our 2 storey extension is in the region of 30m2 and it costing us a few ££££ more than your quote and that includes VAT.

[tillson]

Thanks Bob

I am located in Derbyshire, midlands. Ground in mainly clay based and 2 and a half of the 4 walls that will form the new extension are already built.

I don't won't to screw the builder down to the bare minimum, just a fair price for a fair job. I am still waiting on 3 more quotes so maybe they will be closer to my expectations.

Thanks for your input anyway.

Regards
Tom

[Will_it_make_me_rich]

I'm located in Derbyshire, our foundations had to be 2.2m deep do to the neighbours trees.

[tillson]

The price that you have been quoted for your 30 m square two storey extension: To what extent will it be finished?

For example does it include plastering, plumbing, electrical work, joinery etc?

Thanks

Tom

[darrenkellum]

Hi, i thought i would post in here as well as its the same topic.

I am having quotes though at the moment for a small extension (about 12 ft by 8ft) and converting an existing coal shed into a shower room/wc.

At the moment we have said that we are paying cash and the lowest price have been able to haggle to is £22500 + Vat so £26437. We have had a couple of quotes and both are around £25000. We are in Guildford Surrey.

We are trying to get closer to £20000 but it seems this is near enough impossible. Does £25000 seem reasonable to anyone?

Thanks
Darren

[tillson]

A friend of mine is having a toilet block / wash room built on the end of his business showroom. It measures 16' x 8' has a sloped tiled roof, built from block and rendered. Price for this with plaster finish, with all services electrical and water, excluding tiles and hardware is £12000.

I am going to ask this same builder to quote for my kitchen extension mentioned earlier in this thread. I have not had my other three quotes back, but I am starting to get the impression that £35k is an inflated price.

[tillson]

Just had another quotation for my 3m x 4m extension of which 2.5 of the walls already exist and the internal block wall to form the shower room. £50000. This is basically to provide the shell, so by the time I have added the fitting and kitchen units it will be well over £60000. This equates to about £5K per square metre!

I am no builder, but something doesn't add up here. I have just seen a TV programme where a couple completely renovated a badly neglected cottage and added a two storey extension of greater area than mine, supposedly for £25K.

[Will_it_make_me_rich]

Originally Posted by tillson

The price that you have been quoted for your 30 m square two storey extension: To what extent will it be finished?

For example does it include plastering, plumbing, electrical work, joinery etc?

Thanks

Tom

It includes plastering, plumbing, all electrical work, joinery, fitting new bathroom, fitting new cloakroom suite and fitting new kitchen/utility room.

All we have to do is paint it afterwards.

[shona]

Does anyone have an idea of a ball park figure for an attic conversion per m2? Will need beams moved as are W shaped at the moment.
We wouldn't need a dormer though as there's plenty of headroom - velux windows would do.