Another extension cost question!!

[morethanmama]

We want to put a large extension across the full back of our house (the current back rooms are very narrow so we hope it won't turn into a cave in the middle!).

Anyhow, the house is detached and approx 12m wide and we want to come out about 4m double storey. Does anyone have any idea as to what this should cost? I have seen £1-1500 psm quoted but am hopeful that there will be some economies of scale in a big job!!

Also, we need to get an architect to draw up plans. What is a fair quote?

Thanks in advance

The architect can give some idea but best to speak to a builder once the plans are drawn up.

FWIW, our one (not two) storey extension on a house of similar dimension very roughly cost £60,000 including architects costs.

Do you intend to stay in the house during the building works? If not, you have to factor in rental costs.

It is not twice the price to do a two storey extension over a single storey as the second storey only has the extra walls, if you were building a single storey it would still need foundations and a roof. Sadly there is no bulk buy

I am mid single storey extension, mine has worked out to be £1600 psqm but it really isn't just about the cost of the build it is also about what you are putting in the extension.

Mine is a kitchen extension and it is costing the same again for the new kitchen, local fitter, the appliances, new radiator, flooring, lighting etc

So my tiny 3m extension on just 2.5m wide kitchen is 7.5m sq in total and will cost £12k just for the building nothing inside. I'm in Yorkshire so we drive a hard bargain but to be honest £1600 psqm is about right round here.

Tganks for the replies. Wow, 1600 psm just for the build. I had thought that those figures would include basic fitting out.

Surely though for a bigger space there are some economies of scale [hopeful].

We have a budget of about £100k but for that I want to put in new boiler and bifolds as well as ensuite etc. will need a new kitchen too. So very interested in peoples cost saving tips.....

I mean thanks

Blueshoes, did that include the kitchen cost? When did you do your renovation?

morethan, we bought the house in May last year, got planning permission in Aug and moved in Jan this year, with certificate of completion issued March

We did more than just the back extension and so many of the costs (e.g. flooring, decoration gets lumped in with other costs). My £60,000 figure includes all decoration and flooring but I think you might struggle to include the cost of a kitchen in there. Our kitchen which is large-ish with many fitted units was £14,000 but as you know, you can go nuts on the kitchen which we did not. In addition, you would want to add on the cost of white goods as well (like cooker, dishwasher, washing machine ? if you intend to have a washing machine in the kitchen).

It was really hard to get the builder to give a ball park figure though. He would give a quote item-by-item but then I find he did not include other items (like architraves, doors, patio windows, cost of flooring, paint). So you should budget for not only cost overruns but also this stuff that comes out of the woodwork!

Cost saving tips ? my builder, haha. I love my builder ? which is a rare thing even after having used him for major work. I?d sooner give my dh up than him. Where are you, morethan?

Think carefully about whether to rent or live in the house during the construction. If you can somehow cordon off the back to leave you enough room to live in the front of the house, then you can try doing it. What you want to avoid is builders having to clean up every day to make the house liveable for you, because that would be paying builders? wages to do cleaning and would add to the construction time. If you rent, you find that the savings in construction cost might outweigh the cost of the rental. So do have that discussion with your builder.

On the kitchen, we went to Magnet which had a free designing service but then gave the work to a carpenter who gave us a bespoke kitchen based roughly on that design.

You should be able to get economies of scale, after all the architect?s cost (I went for fixed cost rather than percentage of the project cost), the cost of the foundations and building inspector will be largely the same. I am not sure you will get bulk discounts on materials - at the end of the day, this is still a small project in construction terms) - but the builders? time will be more efficiently spent. They charge by the day and so with a bigger project, there won?t be as much dead time whilst the builders are waiting for other stuff to happen? Speak to your builder, obviously!

Sounds like us, the whole house needs redoing plus the extension. Arrrgh it's going to cost thousands isn't it??!!

Sorry as far as construction goes this is still a tiny project so economies of scale really won't be a factor.
How much it could cost is dependent on many things (finish, fittings, complication, ground conditions, drainage requirements, site accessibility, speed of build) so rough ideas should have a hefty contingency.
If you want to meet a local architect who could give you pointers as to the viability of the scheme google Tea with an Architect or Architect in the House which are events run by the Royal Institute of British Architects as part of Architecture week this summer.

It will hurt, but it is a good hurt once the house is done.

On top of the back extension, we did a loft conversion/dormer extension, re-wired the house, re-jigged the staircase, practically gutted the first floor and re-decorated the whole of the inside.

It was fairly no-frills and we kept a beady eye on costs but it still cost a lot more than £60K!

I'm in Bristol. We are desperate to get on with it now as we have been living in a hovel for a year.

Interesting what you say about moving out - yes I think that we would try to. I have 3 under 5 so might be a bit of a nightmare otherwise.

Bristol might be a bit far for my builder, as he is based in Essex and takes jobs in London.

For a big project and with young children, you also need to think about who is going to project manage as you probably won?t have time or expertise. Architects can offer that service but it is pricey. My builder did the project management and so that kept costs down. FWIW our architect was fantastic at the creative side/design but probably would not have been so good at project management, as we felt his practical common sense and organisation was not all that great ? it is a different skill set. But we used an architect who worked by himself as opposed to an architects firm.

Builders dust cannot be all that good for young children, plus the danger of the tools and materials lying around. Unless the rest of the house is big enough for you to spread out into (but bear in mind at some point you won?t have a kitchen) and to cordon off the back construction, I think it is best to give moving out (at least for the period of the worst

...construction) serious thought.

We are just a bit further down the line than you, but planning a similar size extension. Ours is about 11m wide, and going out 4m, but single storey. We have spent out over £1k so far on getting drawings done, and have been given planning permission. We are trying to get quotes - so far these have been pretty eye watering. They are all coming in around £100k + VAT, although we think there is some scope to 'value engineer' the project to cut out some costs. (We're in SE London btw).

One of the added complexities of ours is that we have amended the plans to better suit our neighbours, but this means more complicated steels in the roof, and a more difficult build.

My fear is that we decide to go ahead and then more costs appear - I think we would struggle to afford much over the quotes given. It's a big decsion!

When doing anything that involves a builder, get 3 quotes, take the most expensive and then double it. That way you won't be disappointed when there are unexpected extras. There are ALWAYS unexpected extras. We've renovated a very old listed cottage and put an extension on, and unexpected extras have included, among other things, bat surveys, the footings of the extension needed some really clever work by an engineer due to the combination of clay soil, a spring, shallow footings on the old house, and some tree roots (all of which were only discovered after we had started digging,) and a whole new roof on the old bit due to it being about to fall off! We needed underground pipes and the mains electricity supply (which comes in by an overhead cable) both moving to be able to build the extension.

Don't be hopeful it will be cheap, and you won't get disappointed . Sorry if this not what you want to hear!

On the issue of moving out, you also need to take into account the season/weather. By the time the architects are hired, the drawings done and you get planning permission, would that take you into winter? You don?t want to live in a house with 2 storey hole in the back during winter!

For a ball park, perhaps ask an estate agent?

The house we bought was crying out for an extension (probate case) and all the buyers who had youngish families were looking at the extension potential but needed guidance on the cost. The estate agent came in almost spot on at the total cost of the extension. We initially thought it was high but in the end it did came up to there.

£100k sadly doesn't go far when you have to factor in VAT & Kitchen.

Excluding VAT the spend is circa £80k - maybe take off £20k for a new kitchen so you are left with £60k.
It will take 12 weeks approx - 60 days - my builder worked on approx £500 per day (for a basic team including labourer). That's 30k.
Plant& skip costs are high and run into thousands. Add in the material costs - tiles, bricks, plaster board, electrics, windows, doors, decorating and it soon adds up. Architect fees, planning and building regs are additional.

Also consider what might need to happen to the garden/patio post build and add in costs for replacing patio as we forgot this cost and it wasn't trivial!

I watch the house build program and never, ever understand how they build an extn for £10k..I just can't see how it happens as there are costs you can't avoid.

I think most people under estimate the spend but equally most people never regret the work being completed.

Our 2 storey extension along the back of the house is an extra 100sqm and we've got 3 rough estimates of £150k. I'm going to source the kitchen, flooring, bathrooms, interior doors and am hoping to save £15k, we've compromised alot too - Original spec would have been £170k.
We're also going for a fixed price and time = peace of mind.

We built a 6x6 m double storey extension so 72 Sqm in total which came in at 70 k for the basic bare shell I.e after plastering. This is before vat! Then you have glazing, plumbing, electrics, tiling, flooring, decorating on top plus any kitchen or bathroom fitting.

For your 12x4 m double storey, I would be expecting quotes around the £90k Mark for the basic shell excluding vat. 1St and 2nd fix finishes will vary enormously but you will spend at least that amount again for a modest finish.

Unless you will be doing quite a bit of the work yourself, I don't think your £100k will stretch to a 96 Sqm extension. If you take away vat and fees, you are actually left with approx £77K.

I would also recommend planning your patio when you are having the groundworks done and the digger is there - it'll be more expensive to have it done afterwards so budget for this too!

I feared that we were a bit light on budget.
Having said that, we had an architect round today who thought that the build with a basic kitchen would be 45-50k.

I had forgotten about vat

I know a good builder who did my friend's extension with kitchen and has done lots of work in my own house - let me know if you want details (they are in Bristol). I have no interest in the business by the way, but have been really happy with their work.

That would be great. Could you pm me. Thanks.

Foundations works or any digging down is a total unknown in the building industry. No one knows what is in your garden. My simple kitchen extension mentioned upthread was £1600 psm including VAT.

We paid the builders merchants directly (builder orders, we pay) and we paid the builder a weekly wage. Plus all the sub contractors I pay directly, in my tiny 6m long kitchen x 2.5m my electrician's bill alone is £1200, as we had a shower cable put it, 8 LED downlights (cables only we are supplying the lights) outside lighting feed, outside socket, new cable for 3 outside lights. Plus the usual supplies for the kitchen, sockets, and feeds for oven, hob, combi microwave.

Our kitchen is Ikea, units alone are £3.5k for a 6m x 2.5 m run and I have been researching stuff for over a year. I have shopped around for sinks, taps, appliances, worktops, lighting, flooring, and glass splashback.

I did also research a single exterior door with an internal blind (like bi-fold but only one door) the cost for just supplying one single door was £1300

My house is only 13 years old so no scary oh no look what we found when we removed that wall type discoveries.

I have sort of project managed it because it is so small and we had already made all the decisions before the builder started. I am a SAHM with two children both in school so I have been here for all of it, and a hell of a lot of work goes into a tiny extension. I am 10 weeks in and kitchen fitting starts tomorrow.

In the last year I have designed several domestic extensions - the range of costs per sq metre varied beween £800 for a simple flat-roofed cavity wall 'box' up to £2,600 for a two storey stone and slate double bedroom, ensuite, dining and kitchen 'T' shaped structure with a very high shell and fittings specification on a Grade 2* listed building.

As regards fees, I charged £650 for the former and £11,500 for the latter (but that did include structural engineer and SAP energy calculations).