Cost of extension - ball park estimates

[bungalowroofonit]

Has anyone got any knowledge of extensions costs that they could offer in relation to the following:

We're looking at extending a small semi-detached bungalow - upwards and outwards.
The rear outwards (single storey, flat roof with veluxes in for light) extension - 24 square metres - will span most of the rear elevation and have some sort of french windows, sliding/bi-fold doors aspect with kitchen plumbing connection down the side where the exsting connections already exist. Other than that - nothing dramatic.

The loft extension will be a hip to gable roof re-alignment and have a new staircase rising from an existing living room. The loft will have 2/3 velux windows to rear only and will be one bedroom with ensuite shower and loo.

The existing footprint of the bungalow is about 50 square metres - I don't imagine the loft bedroom being more than 12 sqmetres - ish - plus the ensuite (built above the existing bathroom)

Planning wise - other bungalows have done different variations of this work - one or the other type of extension - only one other has done both.

We're hoping at £60,000 or less for both together - naturally as much less as possible - so that we could then buy kitchen white goods and maybe get a small driveway done.

Is that a crazy underestimate? So far we've been going by budgets on TV programmes - have no extension building experience at all but have done a couple of small redecorations/refurbs of flats.

It may depend on where you are but £60k could be on the low side. An extension is around £40k including VAT and windows and bifolds. Ready made stairs can be £400 but if bespoke stairs are needed then the costs rise to around £2k. A loft extension requires structural work so difficult to estimate as it depends on the individual house but steels with calcs could be about £3k. Are you planning on raising the roof - does it have 2m clearance now?

You will need to set aside fees for plans, planning, building regs and steel calculations. Architects can charge anywhere between 2-5k.

We are going through a similar project and the costs of materials for rebuilding are surprisingly - insulation can be thousands, cost of skips have increased and builders in the SE are very busy so can charge high daily rates.

Have any neighbours did something similar? If so you might be able to get a view of costs from them. Also could you phase the project over a number of years os that you spread the costs?

Thanks newstart15 - lots of stuff to think about!!! We won't be raising the roof - the apex is higher than 2m - not sure how much exactly but a fair amount and other neighbours in same houses have done similar lofts so we're fairly happy than it can be done - it's just what price can it be done at!!!
The house is so tiny that we couldn't be in it at the same time as builders so we want to do everything that needs doing (it hasn't been touched apart from a new boiler a couple of years back) in one fell swoop - and hoping that approach makes it a more appealing project to a builder.
We're hoping to get one builder who will do the lot rather than employ separate contractors - we suspect that may work out more expensive but less traumatic - not sure - what have you done?

I don't know where you are in the UK but sorry to say the rear extension alone before fit-out in the south east would be in excess of £60,000.

Thanks for the feedback @concernedabouttheboy - what kind of figures are you basing your thoughts on?
All the internet stuff I've read gives estimates of £1000 - £1200 per sq metre - even if we built 40 sq metres at £1500 per metre it still only comes to £60k!

Obviously real life is different to the internet and I'm not a builder, so any real world figures/costs you can give would be a great help.

We have recently had a rear extension and remodelling of existing rooms at the back of the house. The costs were roughly £47k to builder, £8k for bifolds and widows, £4k for floor, £15k for new kitchen (all inc vat). We are in bristol.

Basing it on quotes we have recently had for our rear extension. £1000 psqm waaay too low for south east. Ours will be 7.5m by 3 m, some steels, no bifolds, no interior fittings included in that.

Sorry I forgot the important bits- the figures!

Our quotes ranged fron £70,000 to £130,000 for a fully managed build but the latter figure was still without the kitchen + small bathroom sanitary ware .

A standardish loft conversion down here would be around the £40,000 + mark. Several friends have recently had theirs done.

Not expressing myself very well today. The £130000 was for a fully managed buikd, £70,000 was managing it ourselves.

Many thanks @ concerned & @ marmite - wow! those figures are really staggering!!! I'm in the wrong line of work - that's for sure!

Having angsted over costs and spent a few hours in the loft going over measurements, we've decided to abandon the loft conversion aspect - we'd probably have to bend down to get past the end of the bed!!!

What we'll go for is as large a ground floor extension as possible and insulate and board out the loft with light and power, a decent ladder and maybe a couple of velux windows - make it possible for someone to use it as a functioning hobby room/small office - but nothing more adventurous that that - no hip to gable conversion business alas.

In terms of costs - the rear extension is really going to be not much more than a big room with base level kitchen units on one wall incl cooker and sink. All the practical stuff/white goods will be kept in the existing kitchen which will become a utility room. The other side of the room will be a large ling area. The walls will be painted block finish over a standard wood floorboard floor. There'll be a flat roof with a couple or 3 large veluxes in the roof. Don't know about bifolds but definitely as many glass doors as we can afford.

I can't imagine spending more than £3k on a kitchen - this is a 2 bed bungalow and will never be big enough for a 'family' - most would only ever be 3 people and the area wouldn't justify huge outlay on uber jazzy kitchens or finishes.

Surely 20 - 30 square metres of that can be done for less than £60k ....

I think if you are not in the south east that will make a huge, huge difference. For comparison, my parents had a kitchen extension done (about 4 x 4 meters), completely new kitchen around the 8 k mark, new flooring, some internal walls removed etc., and it came in around £25 k I believe. They are in the midlands. We have seriously considered paying their builders to come down here and us put them up in a B and B for the duration of the build. This would still be cheaper than us getting local (to us) builders to do it. It's a mad, mad world.

I'll be surprised if our house renovation and two storey extension comes in less than £350k no matter what the builders are saying. We are in London, so everything is £££ and I've watched too many property programmes to be fooled by a low quote....

£60k inc VAT for a single storey extn would be more possible although I'd just thought I'd break down the costs as it's easier to see where the money goes. We were told £65k for our basic build by architect which was way, way too low. I suspect if he had said actual estimates we may not have gone ahead!

• Fees - architect, planning, building regs - minimum for council will be £1k but you will then need professional fees to draw up plans and building regs. We had quotes between £5-10k
• Basic build of extn - look for any inhibitors such as main drains which can drive costs sky high. Foundations are now dug deeper than older houses which add costs.
• Windows and bifolds - you can shop around but from memory the bifolds were around 1.5k per metre width.
• Kitchen - a very basic and small kitchen can be 2k but you need to include appliances and tiling. Granite is popular but typically >1k and fitting is not cheap as it requires specialist skills.
• Boiler and new radiators?
• Electrics - rewire or new fuse board?
• Patio/driveway - if you are building over existing patio then factor in new patio costs.
• Flooring & general decorating - we spent 3.5k for supply & fit wood floor in kitchen and extn and it was midrange.

Building costs have really escalated in recent years - steel costs go up on a regular basis due to worldwide demand. We are having a loft conversion and the insulation alone is £2.5k! that's the trade price to the builder. Another example are Skips which are now very expensive due to recycling requirements.

I think some housing renovations programs seriously under estimate the costs and it does lull people into false sense of what is actually possible.

that breakdown is really helpful @ newstart - exactly as you say, having watched the £100k house on bbc2 recently (dealing with renovations all under 100k) we've certainly felt we could do a lot for £60k - it's clear though that many mumsnetters have whacking great houses or small houses in lovely areas and with lovely budgets and we're probably talking about different 'milieus' of house and build - I've probably not given enough information for people to judge.
The house we're in is a pre-war 2 bed tiny semi-detached bungalow built for tiny pre-war people. Although we're in the south east, the area and type of house would mean that the average price for a 2 bedder outside of Whitstable is under £200k probably nearer £180k sooo our £60k budget would represent a third of the value of the current house which might be worth £250 when finished.
Of course, materials cost what they cost and labour costs what it costs regardless of the type of property but it's reasonable to say that a builder working on a £1million pound house in the same area would charge more for the same project than they would for our £180k house - economies of scale, perception, and expectations and what it's possible to charge - the difference between the cost of the project and the amount the builder actually charges will vary according to what the builder thinks he can get while still doing the work and making a living - no builder will think they can charge £350k to extend our house but they might charge that to extend a house in Dulwich even if the 'cost' is the same as on our house - human nature innit!!! Least - that's what I hope!!!

The rough guide of 1,200 - 1,500psm is probably reasonable outside London / SE England.

A flat-roofed 'box' on the back of a bungalow is generally a fairly straightforward job apart from waterproofing the junction of flat roof to existing eaves which is sometimes quite tricky.

In the last 2 years I have designed 8 of these, all approximately similar floor 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! :)

Have you approached any architects yet?

@TrevaronGirl - that sounds like the kind of figures we had initially conceived of/imagined - at the moment we're trawling through local builders' websites and generally researching and establishing/fine-tuning what we want/can afford.

One builder whose website/work gallery looks good offers a 'drawings' service - is this adequate?
Do you think small builds like this warrant an architect - I wouldn't know how to choose one or really what to expect or how much we could reasonably expect to pay.
They make me feel like solicitors - you never quite know when the clock is ticking and the bill rolling upwards....
Would an architect 'price' the work and recommend a builder? Or do they project manage/oversee a builder? Or just provide drawings for a builder to interpret/work from?

If you can ingaine what this semi-detached bungalow was like before any of the work (no loft, no extension) then that's roughly what we're working with

www.houzz.co.uk/photos/13479985/craigleith-contemporary-exterior-edinburgh

and we'd love to have the sort of extension that has been achieved here but it would be way beyond our budget and proximity of neighbours and our design preferences would mean no glass walls to sides of extension and budget means no loft conversion but we can dream - we're aiming for the scrimpers version of this - so pretty much mainly a box with some kind of glass doors to the garden and velux windows to the roof.

The old kitchen will become a utility and we'll try to replace all the old radiators (we have a new boiler), rewire, redecorate, board loft and maybe get a driveway put in..... all for under a tenner!!!

if you can imagine...

It's worth having a look on your council's planning website and see what others have done - the names of the architect/planner used will usually be listed as well. If you are planning on an extension then you could get some builders quotes. The clearer you are about what you want then you'll get more accurate costs.
An example - would you go for skylight in a flat roof or a lantern design. Do you plan to live there long term or resell? Sometimes it's best to have a few features as a 'cheap' extension can be very obvious. We spent more than you thought we would on our wood floor but it is fab and always get positive comments and will definitely help to sell the house.

bungalowroofonit

Would this warrant an architect? Well you never know unless you ask... :)

I have been in practice for a few years now, however when I started on my own I would often take on almost anything, charge a ridiculously small fee and work for hours and hours creating what I fondly imagined would be something "wonderful to surprise and delight' the client. More often than not the client would be surprised but thoroughly not delighted because my vision and creativity had produced an unbuildable and wildly overpriced extravagance. "We only wanted a simple cheap extension!"

Needless to say I became a little disillusioned at times. :(

Nowadays I am much more pragmatic and although I take on almost any type of commission I do 'vet' my potential client to ensure that we have some sort of rapport and are at least likely to find some common ground and work together. This I do by offering a free hour or so ( the "or so" means I like them and they provide nice coffee and cake ). During our first meeting I use the time to explore not just what they want, for example an extension this big with a kitchen here and a wall knocked through there but what they may need - more space for growing family, an office to work from home, or simply tired with the current facilities. This enables me to understand their situation and the potential changes and thus with discussion, a few sketches (and more coffee) I can usually offer some alternatives to their original ideas.

Sometimes this backfires and I end up recommending that the best possible course of action would be to avoid the months of waiting for planning and building regs consent followed by further months of construction activity and move house. This of course means I talk myself out of a commission however I take the view that embarking on the wrong solution would be bad for the client but worse for me although, when desperate for work and the potential client is adamant that "this is what I want", I have on some occasions simply gone along with their wishes, prepared the drawings and taken my fee with a smile.

Oops, this has gone on a bit hasn't it? Sorry :)

Short answer - if you ring around a few local architects it is likely you will find some local Trevarons who will come round for a free consultation. Other possibilities are, yes builders do offer drawing services but usually this will be just to translate your proposals into an application and there are also others who will provide drawings - architectural technicians (sometimes called technologists) or 'architectural consultants'. Non of these are architects but quite able to handle an extension (and possibly cheaper as well). Building surveyors are another alternative. Or look in the local free paper for 'building plan drawers' often quite fast and cheap but be careful...

The other questions?

Fees – well I have charged as little as 600 and as much as 7,000 pounds, dependent upon on workload, complexity, and whether or not I just prepared the drawings and stopped there or designed and managed the whole project.

'Pricing' the work – well from past projects and sometimes using services like BCIS or price books / websites like Spons, most architects can provide a reasonable budget figure.

Hope this has helped!

I should have added the following disclaimers:

1. We are completely renovating and extending a four bed house, two storeys

1. The house is in rip off London, worse, in an affluent suburb where every builder and architect is seeing £ signs as soon as I contact them

1. We may have to relocate a tree

1. We definitely have knotweed to clear

1. We need a new roof

1. We need all new bathrooms, kitchen and wiring, plumbing, insulation, underfloor heating, all new furniture etc

1. We need to relocate the staircase.

1. We are dealing with a draconian conservation area who I gather are not likely to make it easy for us.

So this isn't a simple extension, and hence the big estimate. That's not an estimate for anything very high spec either. I'm budgeting £2000 psm and that's only because we know the builders we will likely use.

@ Apatite1 - I don't envy you that - there's a peculiar relationship between builders and punters - whatever end of the market you're at somehow builders are always able to price at more than you would expect/anticipate regardless of the job - there must be a punters bank account psychic reading course (Rightmove Sold prices) that builder's take - just so they can pitch a quote above what you want to pay and then make you feel grateful by dropping the price a smidgin, as a favour, even though it's costin' them!!!

@TrevaronGirl - thanks for the essay;-)
And I can see the point when you put it like that - after all, we've all had builders round who offer 'advice' on where to put this, that and the other, suck their teeth and 'advise' against something else and in the end, sometimes only after it's finished, you realise that the tail has been wagging the dog and you've got a job done which is to the limits of their abilities or interest rather than the job which is possible or what you really wanted - it's disappointing.

So often they tailor what the recommend to what they can or want to do rather than what can or should be done - especially if it means they should pass the work on to a more able contractor.

There are aspects of what we're planning which are causing us problems - such as we will have a huge new living area but still two tiny bedrooms without much room for wardrobes - but how do we change this without knocking down every internal wall?

We've dismissed these kind of changes as they seem unachievable on our budget - but as you say - how do we really know until someone with knowledge and a creative eye looks at it - not someone who just agrees with what we've come up with - very interesting - thank you Trevaron - case well made for consulting an architect!!!

I would recommend an architect however it can be difficult to get the right one for you so do invest time speaking to a few. My friend had an architect who recommended moving the front door on her build, it was such a clever idea and changed the whole feel of the house. I think you need to consider how long you plan to be there and what the options are i.e £60k gets you xyz but £100k would get you abc

We used an architect and I am so glad as she came up with really good and creative ideas. We had her back a couple of times during the actual build and again she came up with some minor changes that made a big difference to the end result