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How much for a 2 storey extension?

(13 Posts)
boardergirl Mon 27-Jun-11 14:45:55

We have looked at an older 3 bed semi with a detched garage (about 6-8ft away from house).

It has adownstairs bathroom so I was wondering how much roughly a 2 storey extension with an intergral garage would cost. I realise we'd prob have to knock down existing garage, they have a small extension to the side of the dining room would we have to demolish that too?

The extension would be a single garage with a small room behind and 2 bedrooms or 1 bedroom and bathroom above and a pitched roof if that makes any difference cost wise.

Also what kind of costs would we have to figure in for planning permission and creating an upstairs bathroom (just the plumbing we would probably fit the bathroom itself)

Pendeen Mon 27-Jun-11 15:38:35

Unfortunately there are so many factors to consider when estimating the cost of alteration / extension projects without seeing the site, the locality (e.g. central London would be much more expensive than the north of England) and so on.

A (very) rough rule of thumb is: the smaller the job, the greater the cost in £ per square metre. For a two storey extension you could be looking at between £1,200 to £2,500.

Architect's (or other building designers) fees are negotiable but for planning consent drawings, producing a Design & Access Statement, buying a location plan, etc I would usually charge @ £800 - £1,200 providing there were no "oddities" - for example conservation area, national park, flood risk area etc.

Drawings for building regulations approval and construction would be extra.

Flat roofs are usually cheaper than pitched but most councils will not tolerate (quite rightly IMO) two-storey flat roofed buildings or extensions.

Planning fees and a lot more useful stuff is here: planningportal

Not sure about your last question - is this a separate job?

SherlockMoans Mon 27-Jun-11 15:51:08

This is really a "how long is a piece of string" question depending on what you want. Do you know anyone who has done similar work locally, could you ask their builder for a quote.

We used a local architect both times we built and tbh he saved us time and money - he know roughly what the planning dept would accept and managed to avoid us having to put in an extra telegraph pole the 2nd time (saving us more than his own fee)

Think carefully also about the effect any extension will have upon light into the existing house (an error we made in the past)

You should be able to get details of the planning costs from your local planning department website - you do have a certain amount of permitted development before you need to plan but its a while since I did this and there are exclusions.

I would say also allow 10-20% MORE than what you are expecting to pay for the unexpected it takes a lot of stress out of the situation as it never costs exactly what you think it will.

Oh and use good people, not cheap - not saying that someone cant be both but the quality is way more important than the cost long term.

SherlockMoans Mon 27-Jun-11 15:53:24

Im quite jealous actually, I really enjoyed it...cant do any more here and often look longingly at houses with tempting gaps to the side of them grin I probably need to get out more

SherlockMoans Mon 27-Jun-11 15:55:37

Hmm just realised you said "older" also be careful, friends of ours decided to build onto their older property but when they started realised the house effectively had no foundations so had to start with some kind of underpinning before they could start.

boardergirl Mon 27-Jun-11 16:55:16

Thanks both of you for your detailed info

Pendeen do you mean roughly £1,200-£2,2500 per sqm for each floor? I suppose bathroom would be separate job.

SherlockMoans do you think its worth using an architect even for a simple job? The house is fairly cheap on for £189k for 3 bed so will not be a luxury 4 bed when possible extension done.

I also spend toomuch time looking for houses with side gaps/garage potential!

Pendeen Mon 27-Jun-11 17:11:34


No, it would be the area of the ground floor.

As to your second question (not to me but I will be cheeky here) obviously I would say "yes" but not only because I would like to keep my fellow architects in work!

Good design is about so much more than drawing a plan. Find a sympathetic and friendly architecht, use their experience and creativity and you will probably find that their fees might be quickly saved by careful and imaginative design.

SherlockMoans Tue 28-Jun-11 11:56:11

We used a local architect both times and personally I would always go that way. We needed drawings for both the planning process and for the builder and he suggested problems and ideas that we had not really considered ourselves.

The only time we didnt use the architect we ended up making the house too dark!

boardergirl Tue 28-Jun-11 12:11:50

Thanks will be finding architect if wedecide to offer on this house

SparklePrincess Wed 29-Jun-11 18:42:28

In general, unless you plan on staying there forever, it is not financially viable to put this form of extension on a semi detached house as you will never recoup anywhere near its actual build cost.

Pendeen Thu 30-Jun-11 14:28:04

I wasn't going to comment on the value vs cost isue but I think Sparkle is quite right.

That is often the comment I offer to prospective clients: think hard about the cost and the disruption before going too far. I have lost count of the number of potential commissions I have talked myself out of. I will never be a millionaire at this rate!

A valuer (Chartered Surveyor) could offer advice on the likely increase in property value.

boardergirl Thu 30-Jun-11 22:58:30

Had been thinking that myself sparkleprincess.

Not sure about this house, partly cos of downstairs bathroom and partly cos of lack of space around front of house.back onto rightmove I think!

Pendeen you seem a very honest architect!

SparklePrincess Thu 30-Jun-11 23:35:33

The best thing to do is to buy one somebody else has already extended. Thats what im hoping to do. smile

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