Detached Extension - 2 storey

[Homeowner251]

Evening all,

I have just started the process of looking into extending my house. When I say started I mean I have contacted a draftsman who is preparing the drawings (it’s currently a 2 bed detached house, which I’m looking to extend backwards to a 3 bed, with a larger downstairs living room and kitchen) within the 8 metre boundary for planning permission, looks like I just need building regs aslong as it’s same height at the current house (again this is only my research please correct me if I’m wrong)

I know I’m asking how long a piece of string is, but can anyone throw a figure at me please? I have no idea at all, has anyone had a recent similar size extension please? I’m guessing between 30-60k? I’m based in Staffordshire.

Many thanks x

Without knowing the size it's impossible to guess but I'd suggest around £3,000 per square metre without the kitchens / bathrooms / flooring etc.

So you’re looking at a double height story extension? With a new kitchen etc? Impossible to say without sizes and an idea of fixtures and fittings you’re going for but friends in London have just done this and it was just under £200k.

Is it a bungalow? Even single storey your budget is light unless you’re doing a lot yourself.

Thank you both. Apologies for my lack of information! The rear of the house wall width is 15m then I want to go 8m back @jollyjeffrey that’s really helpful 😊

I think you are being optimistic on price. We are in the north and just to convert the garage into a decent extra room cost us £12k three years ago, before the price hikes.

@Dodgygeezer no it’s a house. I don’t need a bathroom or kitchen, so no extras there, an extra bedroom, then the l room and kitchen just extending out for extra room. I was hoping to put a dining table in the extension part, then just a bigger living room really. I apologise profusely for my ignorance in all the extra information I’ve missed out!

@EwwSprouts Right ok, that’s really helpful thank you x

My friend had a kitchen extension a few months ago. Admittedly two walls were moved/hot rid of an a utility room put in.
Just over £200k.

@Butterkist8 thank you 😊

8x15 is 120 m2 , double that for the second storey and that is a big extension? You have got to be looking at 250k ?

@Diyextension thank you for that. Like I say I have no idea whatsoever 🤣 much appreciated x

This sets things out helpfully.
https://www.checkatrade.com/blog/cost-guides/house-extension-cost/

Oof OP, I think you’re way, way off with your price.

We’ve recently had an extension done - smaller than yours, 8 metres wide, and about 5 metres out. We were quoted in the region of £150k+ from several builders (and obvs you should keep around 10% more as contingency).

Your footprint is more than double mine, AND there’s a second floor. That’s got to be at least £250k, probably more. The second floor is usually cheaper than the first as no foundations.

Can I just check though - you do definitely mean your house is 15 metres across??? Because that’s a very wide house for just a 2-bed. That’s almost 50 feet wide?!

I’ve got a really wide 4-bedroom house that is laid out side to side rather than front to back, AND an attached annexe to the side and the whole lot - including the two bed side annexe - is still less than 50 feet!

I think you may need to stop and breathe for a minute.

There's no way your house is 15m wide. And I've never heard of anyone putting on an extension that's 8m long. Do you mean feet instead of metres?

If you're right then the ground floor is going to cost you around £300k - £350k, and then a second story another £150k+.

I’m also a in Staffordshire (a really cheap part😅) and my cousin has had her ex-council extended out and up (so from a 3 bed to a 5) and had a very small extension on the side with a toilet/utility and all in its cost her £140,000 but that is with a brand new kitchen, bifold doors etc

Building costs are literally through the roof, OP, you definitely won’t achieve the extension up you want on that budget sadly.

Just to give you an idea, of how mad the prices of materials are right now, DH has renovated two properties in the last two years, the paint he buys Dulux trade super Matt was £32 for 10ltrs last year, now £50. The tiles we bought, were £12 sqmtr last year now £16 sqmtr, exactly the same tiles. The kitchen in the first property was three times the size, the kitchen from the same supplier, same level of quality were the same price! It is absolutely crazy.

good luck with whatever you decide, but make sure you have adequate budget, the price you are quoted will always turnout to be more, as things crop up. There will be some value in it, if you get the planning permission but decide not to do the works, if you decide to sell. Good luck.

I’m assuming your measurements are wrong. We are in your county and have had extensions previously but not recently. First one approx 15sqm inc new kitchen was around £30k (10 yrs ago) second one upstairs only approx 20-25sqm was around £60k all in. That was 5 years ago. We had quotes for both that were double what we paid. I think building materials and labour have probably pretty much doubled over the last few years so a budget of £60k would probably not get very much at all these days.

I think your measurements and therefore your interpretation of the rules are way off. Please pay the £50 or so it will take to have a pre-application advice appointment with someone at your local planning authority to discuss the proposals, so they can tell you for certain whether or not you actually need need planning permission. Some of it will depend on how much of your outdoor space you will be building over, and the proportion by which it will increase the footprint of your house. Don’t rely on people here, or a builder, to tell you what the rules are. It’s your responsibility as the owner, even if the builder says it’s okay.

OP - the 8m limit is for single storey extensions and even then a prior approval application would be necessary.
The permitted development limit for anything above single storey is 3m - anything more than that will require a full application for PP.
There are lots of other limitations too. You need to either submit an application fora certificate of lawfulness to make sure you don't require full PP for your proposal or get yourself a decent Planning Consultant to make sure. Architects often don't know the finer details of the General Permitted Development Order.

It’s really difficult to say what it will be without more info, if steels are required, to what fix the finish is etc, but I would say you wouldn’t get change from 200k probably.

Ask your draftsman.

Whoever you have engaged to draw your plans will be able to advise you on what permissions you need, and also on a ball park figure for costs. If your draftsman can't do that, find another with more experience/knowledge.

We’ve just finished a ground floor extension 40m2 and a bedroom above a single garage. No kitchen or bathroom, but a good quality build, Yorkshire. Worked out at about £3000 per m2.

I think it would be good if you could attach a drawing, even a rough sketch as a 2 bed house with a width of 15 m is very wide. Adding 8m is also a big extension. My lounge is 4.5m wide. That would make your house 3 times wider, unless you are in a converted barn or rope house then you might need to remeasure.

Show the original floor plan (often found on Rightmove under the House Prices header) and then what you intend to add on.

A 15m×8m double storey extension is huge - and you're only getting one extra bedroom plus a larger living/dining room? It doesn't really make sense to do such a large extension for relatively little benefit.

Also, your budget estimates are extremely optimistic. As a previous poster said, £2.5k - £3k per square metre is typical these days.

Thinking about it, you must mean feet rather than metres. Because 15m would be an insane width for a 2 bed house. And there is no way you'd extend 8m just to have space for a dining table.