How much to extensions really cost...

[Holdmydrink]

Just that really, looking for some input to those who have been there and can give some insight into how it came out as. Single story, double story, or even loft conversions!

I'm going to see a property for sale, which needs extra room and over time would need an extension but nervous about costs!

More and more each year until there's a recession and builders are desperate for work again. But I would factor in £2000/m2 as a minimum (I am SE though.)

We had a 2 storey extension in the NW about 2 years ago now and it worked out at about £2k per square metre, plus VAT. That didn't include the cost of the kitchen, appliances, bathrooms, flooring, bifold doors or any decorating - but did include Windows, electrics, radiators, fitting plumbing for bathroom, ensuite and kitchen. We also paid for drawings, planning permission and building regs sign off separately.

Also our back garden was trashed pretty much during the build so that's cost quite a lot (needed work anyway). We also paid for storage of furniture at a storage unit for 6 months during the work and then obviously spent on furniture/ fitted wardrobes etc for new space. It's all the extras that mount up on top of the actual build costs.

Approximately £1.5k per square metre inc. VAT for our almost finished two-storey extension in the north west, to a plaster finish and excluding decoration and new kitchen. Also excluding architect, structural engineer and building regs fees.

They cost more than you think! That is how much.

Depends on:

• Type of extension (single story, double story, side return, loft etc)
• Access e.g. are you building a side return with zero access or an easy single story with access all around?
• Time of year - will you be delayed with weather? Do you need to pay for a tin hat for roof?
• Parking (it is expensive to suspend bays for skips etc)
• Finish
• VAT registered builders or not?
• Other issues e.g. moving drains or meters (expensive!)
• Other add-ons "whist we are going X we might as well do Y"

Thanks all, I'm in the SW. It's a bit daunting, how long did it all take for you guys?

Shit loads more than I was expecting sorry, not v helpful!!

Our loft conversion cost around £50k as it's an L shaped with an additional dormer above our small office/bedroom, it took around 8 weeks to complete during summer.
We're now getting the same company Builders GB to build our side return extension plus a basement conversion our costs will be fairly high because of the basement works and the additional supports required etc, but the others above are about right it works out to just over £2k/m2 for us excluding furnishing and fitting out.
Costs like moving the drains as SushiMonster has pointed out parking permits, fancy scaffolding and accessibility can add a few thousand pounds on to your overall cost too I guess.
Get a few builders round and gather some estimates, use their brains and know-how to see which type of extension design is suitable for your new place, most will know about relevant planning consents and other bits and bobs that you'll need to consider as well.
Having an architect on board is also a wise move but depends on whether your builders are able to provide a proper design and build service or not.

That's really helpful, thank you.

Alex, your link doesn't work.

Ours cost twice as much as originally estimated. Bear in mind that you’re probably not just building, you’ll be knocking down walls and adding in steelwork too, and that’s expensive.

Is the price per square metre per floor or for the house's footprint. For example, for a 6m x 3m, 2 storey extension, would it be £36k or £72k at £2k/square m?

Footprint. You're only building one set of footings, one roof, paying for one lot of building regs fees, etc etc. General rule of thumb is that a 2 storey extension is 1.5x the cost of a 1 storey on the same footprint.

We've just added a 27m squared single extension with wall removals, steel beams etc. It was near on £2k per square metre incl VAT although we went for some upgraded finishings. That included a floor, fitting of kitchen (not supplied) and aluminium framed large patio door.

No the general perception of cost per square metre is on the actual space you gain so 6m x 3m double storey at 2k per sq m is 18 x 2 x 2 so £72k. For the same size footprint bit single storey you might have to factor in a higher price per square metre so say £2.2k or £2.5k.

We paid about £50k all in for a loft conversion.
Standard one room en-suite with a dorma in SE London. That cost includes carpeting/tiling and shower suite.

Our extension was quoted as 43k which would have been doable, had this encompassed everything but we encountered many snags. Adding a new build onto a very old build has actually cost double! DH wishes I had never pointed this out - the increasing costs in an extension goes up in thousands, not hundreds.

For us, damp and roofing issues - including more feasible skylights - an eye watering 6k for one item - poof went the contingency! extra RSJ's. The 5k kitchen suddenly evolved into a 15k for kitchen inc granite. As namechange says, it's the extras like a new patio as the old one was dug up for the extension and new furnishings that we just didn't factor in. The 12 week promise by the builder actually took over 12 months due to builder spreading himself too thinly over several 'bigger' clients. No washing machine, oven, hob or running water downstairs for weeks and no heating for months was pretty grim.

BUT - everyone that comes over says how stunning my home is, I can't see it as I still remember the bitter, bitter, cold PLUS the frustration of still ironing out plumbing snags 3 years on is now wearing very thin.

£20 single storey extension above existing garage creating one bedroom and an ensuite bathroom.