Extension costs critique

[manasota5]

Hi all. Am planning a single storey kitchen extension - 10sqm of additional living space. Trying to avoid a budget disaster. Would anyone who has been through this in the last year or so be willing to critique my estimated costs?

Arhitect/drawing £1500
Party wall surveyor (both sides) £1500
Structural engineer £500
Building work (inc plumbing, electrics and plastering £24k (based on £2k per sqm plus VAT)
Roof windows £4800
Sliding glass patio door £3600
Building regs £600
Permitted dev cert £180
Steel beams £3000
Units and worktop £3000 (probs a bit low, may have to save some more for this)
Flooring £2000
New oven and dishwasher £1000
Lighting £500
Radiators - not yet priced up
Build over Drain cert £400
Total so far: £46630.

Is there anything clearly missing or very far off? TIA.

I think that’s very high. £4800 for roof windows high, steels should be in the cost.

You have priced at nearly £5k a sq m in total.

Find a local architect / designer with links to local contractors and ask them how much you should expect to pay including labour (which you haven’t got in your quotes). Then add 40% for VAT and room for error.

I think you're over estimating. For example paid 4K for 4 velux windows (2 motorised) , 4m bi fold door and 2 other long narrow windows.

We did a 6x6 m extension plus lots of rejigging inside and paid 70k for everything. Party wall agreement was 1k.

I think it's low for the kitchen units/worktop. I had a new (very small) kitchen in 2016 and it was £4000 plus £4500 labour.
Prices vary depending on where in the country you are.

I don't think you're too far off actually. I agree with a pp that the roof window seems expensive and the steel beam and (standard) radiators will often be in a builders' quote although you obviously need to check.

However, a decrease in those elements will be swallowed up by your kitchen. £3k for units and worktops is really low - unless you're having a budget range from somewhere like B&Q with laminate worktops.

Thanks for all the replies. I didn't realise steels would be included in the build cost.

You are very right about the units, I was approaching it with a 'just get it built then sort the kitchen' view. I will try to find more funds for this, or rejig existing. Was going to go for fairly basic cupboards but an expensive-looking stone-based worktop.

Put a few hundred to one side for your next set of utility bills, and take aways while you have no kitchen and I don't think your far off in total but have gone over a couple and under on others in my opinion. Looks realistic for totally finished £ per m².

Flooring seems pretty high for a room that size. Builders get massive discounts at tile shops for example. If we'd purchased ourselves we'd have paid 4 times as much as our builder did for the same.

@ShellieEllie

Flooring seems pretty high for a room that size. Builders get massive discounts at tile shops for example. If we'd purchased ourselves we'd have paid 4 times as much as our builder did for the same.

The extension will add to an existing room, so overall flooring will then be approx 38sqm (8.2m x 4.6m). Want amtico type ie hardwearing nice-looking vinyl.

Will definately try to work with a builder though to get a discount. Thanks for this tip.

We’re currently doing a single storey extension and I think you’re about right. You may not need a party wall surveyor if your neighbours are happy to just sign a party wall agreement (ours have been in both our current house and in our previous house when we extended). I was going to say your flooring costs are high but now makes sense based on your comment above.

Do make sure you get a number of quotes for the building works as we found they varied enormously. I’m now project managing the build myself and getting different trades in as it means we could save a lot of money. Do bear in mind though that the smaller the extension the more expensive it generally works out at per m2.

I think you are about right on costs. Although £2000 per m2 is often mentioned for a small extension it is often higher because you don't have the economy of scale.

We paid about £1k per steel in our build plus fitting. I would expect the windows you have priced for to be quite high end, aluminium slim framed.

You will only get a very basic kitchen for £3k. I assume you have a fridge/freezer, sink, hob, tap, extractor already?

I would add a 10-20% contingency fund in case you need deeper foundations or anything else comes up.

Do you need architect drawings ?
Depending on what you are doing, you may just be need drawings which can be done a lot cheaper ?

I'd up the build cost a tad, have noticed costs going up and the figure of 2k/m2 is more like 2.3-2.7k now