Anyone built an extension with SIPs (Structural Insulated Panels)?

[Crumbelina]

Bit niche!

We're hoping to build a double storey extension (9m x 5m kitchen on the ground floor and 4m x 5m on the first floor). We were originally going to use block and brick but we're now interested in using SIPs (instead of blocks) and then stock bricks for the outside. We realise that SIPs will cost more, but I think it'll be worth it.

We've sent out a request for quotes and already had a few rejections (not a big enough project for some companies and one has cited an access issue as we have a detatched house in SW London with a 1m side alley and they like to use a crane).

Does anyone have any experience with using SIPs, or any thoughts on them?

I've never heard of them being used for domestic buildings, but know they get specified a lot of larger scale structures.

I wouldn't have thought you would get the economy of scale on your extension for this to be practical. Plus you'd have an interface with the existing structure so not sure why you feel it may be worth it? If it's additional insulation properties you want you could go for extra insulation in a standard cavity build?

Thanks both. We did have a chat with one company last year at Grand Designs Live who said that it would (just about) make financial sense and gave an appropriate estimate of around £15k (although I'm sure the true cost would be higher).

We're going to be project managing the build ourselves (with DC2 due late September) and so we were swayed by SIPs because of the quicker build time, we'd be slightly less reliant on the trades and the SIPs company would be able to advise and help us with the structural drawings and building control.

This may all be wishful thinking!

We have a single storey SIPs extension. I had reservations whereas DH was very enthusiastic. The panels themselves go up very quickly, so you have an actual roof and walls within days of the groundworks, etc. being finished. I was worried that they'd seem flimsy compared to brick, but I was thankfully wrong; insulation and sound wise, it's better than the rest of the house (Edwardian semi), in fact the SIPs extension has improved the warmth of the house as a whole. It has been 5 years since it was completed and we have no issues, but I do worry that it will be difficult to find easily find a builder to carry out works, should there be a problem...

Oh Plock, I think you've made my day! It's so good to hear from someone who has used them for a domestic extension. You must be so pleased that things went well and it's improved the warmth of the house. I'm not expecting miracles but I'm hoping they might help warm up our Victorian detached house which leaks like a sieve.

Can I be cheeky and ask a few questions please? Namely, what company you used, what size is your extension, what external materials you used (brick slips or something else?) and if you had any access issues during assembly, e.g. if the company needed to use a crane?

Sorry, that's lots of questions!

I'm so glad that I've made your day, Crumbelina! Ours is 4m x 5m and is a covered in some sort of polymer render (my recollection is hazy) in white, which is water tight, breathes and never needs painting, apparently. I like the idea of brick slips; would you be able to match these to your existing bricks? We had no access issues as there is a passageway at the side of our house. The company we used are no longer trading, which causes me to wring my hands occasionally!

Wonderful - thanks so much for all the information! It gives me hope that we'll get some quotes in the next couple of weeks (was getting a bit worried as we got a few rejections and one company said that they would need to use a crane as opposed to our side alley and couldn't quote).

I like the idea of brick slips if we can match them to the London stock bricks we have. I just need to have a look at the sound proofing qualities as our gardens are quite small and it's a bit built up at the back so I don't want our neighbours hearing us and vice versa. As an alternative we might go with normal stock bricks as it could be less controversial with the council/building control.

I've been waiting for 2.5 years and counting for this extension so SIP assembly day will probably be the highlight of my year (oh dear ).

Thanks again!

I've stood outside knowing that the DC are making a terrible racket inside and whilst I can see their mouths moving, I cannot hear their screams .

It's amazing to go out in the morning and return home to find walls where there were none. I'd be surprised if they needed to use a crane, ours were just carried down the side passage. We spent quite a long time marvelling at the walls once the builders went home that day!

My neighbour just finished using this company for a garden room (in sw London), using SIPs, might be worth chatting to them about extensions.

www.bespokesheen.co.uk/extensions

Thanks Plock! Definitely worth me investigating brick slips now if a render/SIPs give great sound insulation. One of the key conditions of permission from the council is matching the brick so I'll see if it's possible.

Madeleine, thank you so much for the link! They're pretty close to me so definitely worth me looking into it.

Interested to know if you are going ahead with the SIPs Crumbelina? Sorry for arriving late and hijacking your thread! I'm interested in a SIPs extension. Like you we have access issues, there will be no cranes or heavy equipment involved!! We also, delightfully, have the neighborhood sewer flowing beside, and possibly under our site! I was wondering if a SIPs build would help get around that problem as it is a lighter construction so shouldn't need such extensive foundations, not sure if I'm right about that.

sara if you are building within 3m of a sewer, you will need a build-over consent from the water company (Thames Water in my area). If the sewer is running parallel to the line of the foundation, it's going to be a tricky little problem for your structural engineer. SIPS are lighter than than traditional B&B but for a single storey domestic extension this probably won't make enough of a difference to affect the build over one way or another.

Ooh, didn't expect this thread to be raised again! I definitely have advice but have to go to bed as toddler loves a 6am wake up. Will update tomorrow.

Just coming back to this. We didn't go with SIPs in the end. Lots of companies refused to quote citing access issues for the large panels and a few wouldn't quote as the project was too small to be worthwhile. The few quotes we did get were very expensive (one was £80k+!).

We then moved on to Timber Frame and pretty much all companies we asked were able to quote. You can find contacts on the website of the Structural Timber Association. I'd recommend going for one that's relatively local (within an hour's drive) so they can come and do site visits, e.g. initial visit, check the foundations are ok for the frame etc.). In the end we can't even go for timber frame panels so it has to be stick build. That said, it means they can start earlier, are less reliant on the measurements being 100% correct and the build still goes up very quickly (1 day for the ground floor!). We're paying around £23k for a double storey extension of around 60 square metres. We commissioned the demolition and foundations from another company (£15k) and after the timber frame is complete we'll be using a brickie to do the external walls, tiler for the roof, window fitter for the sashes, sliding door company etc.

It's a lot of effort, learning and coordination as we're project managing it ourselves but we're in London and this build will cost just under £100k (with a high spec kitchen, appliances, slimline sliding doors, polished concrete floor, underfloor heating). If a builder had quoted for the lot then we'd be looking at over £200k I think!

Just wondering, what region are you in and is it single/double storey? Do you know how many square metres it will be?

Agree with socks - the foundations won't make much difference. We still needed them to be 1m deep for a light timber frame. We've just received a form from Thames Water re the sewer and need to look into it to see what kind of consent we need. Probably should have thought about it a bit earlier!

Hey there. Just came across your thread and wanted to find out how you're getting on? We are looking around something your size including the second storey. I've been looking at SIPs extensively, general build costs have come up at around 150k + vat plus kitchen which is insane. Would love to hear back :)

Hi Cava, happy to update! Off to bed but will post tomorrow ...

Our builder currently recommending SIPs for our single storey extension; we are still waiting for a full cost breakdown but very interested to see how much more expensive it could be...

Cava, we didn't go with SIPs in the end due to access issues (our house is detached but we have a narrow side alley). We've gone ahead with Timber Frame stick build - happy to update if you're still interested?

Looks a bit like this at the moment!

Hi Crumbelina, sorry for the delay. I did not get notified you had replied, sorry about that. Yes, I would love to know how you are getting on and what the progress is like too? Still trying to work out the costs and they are insane.

I would have thought the tight access would have been ok, considering the SIP panels are relatively easy to move :)

Do you think you will reach the 100k budget?

We're getting on well! The timber frame is up, the roof is in progress and the brickwork is complete. I think we're still on course for £100k (it'll be my expensive taste in kitchen interiors that'll tip it over if we do!).

This is a rough outline of our costs (noting London prices, but also that we've shopped around hugely and don't have a builder or project manager as DH is doing all.

Demolition and foundations (15k), timber frame (23k), brickwork (6k), brick materials (5k), roof (5k), huge rooflight (3k), slimline sliding doors (8k), polished concrete floor (7k). Lots of other costs excluded, e.g. planning, architect, portaloos, materials but I think everything for the external build comes to around 67k. Then we have around 20k for the kitchen interior which is doable. I'll be splashing out on appliances but DH will do all the plumbing, electrics, insulation, underfloor heating and fitting plasterboard. The only trade we'll have internally will be plastering.

Unfortunately we couldn't get most SIPs companies to quote as the access is a 1m wide alley and they would be impossible to manoeuvre. Maybe a crane would work but that would be £££. In fact, the timber frame had to be stick build as even the timber frame panels wouldn't fit.

Would you hire a builder and project manager or do it all yourself? Also, which part of the country are you in as I could give some recommendations if needed?

Hey there,

Apologies for the late reply.

How are things coming a long? I did consider doing it myself, but I just don't have the time and or, the full experience. Based in Surrey.

Would be great to hear how you are getting on, with the deadlines and proposed costs vs actual costs.

Many thanks,

Gabi

Things are going well (ish), thanks! Dealing with trades (even those with dozens of good reviews on My Builder) is an absolute nightmare so I think you're making the right choice to not do it all yourself. You need a huge amount of time to be on site and make sure that trades aren't cocking up left, right and centre or taking short cuts to rush on to the next job. Can you tell they aren't my favourite people at the moment.

Timings are ok and we hope to finish the kitchen in May, although we got side tracked by doing work on the garden and spending far too much on having a brick wall built, which is a real indulgence. Will be fabulous in summer though.

Costs are a bit scary! We'll still come in around £100-110k although we've probably forgotten a few things on top of that. Even something like plasterboard and plastering will be around £4.k for the kitchen and bedroom. How are you getting on with your planning?

It's official, I am rubbish, takes me ages to reply, always busy. Dealing with trades can be hard work, specially when so many just take the michael. Not all, but a large amount. The worst thing is when you employee friends, or friends of friends, I won't be doing that again.

That price isn't insane, specially where we are, had some crazy quotes, for a lot less work. Planning is all sorted, just need to find a descent builder.

I changed jobs and that has created some complications in terms of funding, additionally with a single salary it isn't the easiest of things, but should be ok :S

Any pics of your place, sounds great !

Really keen to get started, need more normal quotes and finalise the finance though :)

Again, apologies for the delayed reposes, again.

Best wishes.