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This is more of a comment than a question. For all that the principle of sips has been around since the 1930s, we have found a staggering level of ignorance about them from people who youwould expect better from. At first, just finding builders who were interested in doing the stonework proved problematic as some shied away or I had to explain what sips are to them, even though it's really just like doing it around timber frame. Needless to say we went no further with those ones. Then we found that even our building inspector knew nothing about them & was/is *highly* suspicious of them, querying even their approval status & forcing us to do research for him quite literally every step of the way as well as adding some silly restrictions demonsrating a complete lack of understanding of the system (at least one of which would cause quite a loss of heat if we went along with it). The most recent person has been a window company "surveyor" who has also been very reticent to deal with the build, with some weird ideas (I thus spoke to this big national window company's *senior* "surveyor" about the delays this has caused & had to actually also explain to *him* too what sips are!) At its basic it is simply a much improved form of timber frame of course, but it has been an eye opener at how narrowly educated such a wide variety of the trades are & how nervous at the thought of anything "new". Our builders have just got stuck in, it has to be said, but if I were doing this again, or was advising someone just about to, I'd say to definitely double check that your building inspector had dealt with sips before, ditto any other trades who would be coming on site to interact with the structure - not because there is any issue whatsoever with sips, (in truth a lot of things are actually far simpler with it), but because of how poorly educated the trades from BCOs onwards seem to be about anything beyond brick & block & how nervous they are about anything different & the delays this can cause due to imaginary issues they may develop.

I'm building one! Previous thread for reference: The project is an 8x12 garden building to be used as a standalone utility room for a small house. The ground conditions are solid - outdoor loo removed decades ago, and used as a parking space, then various bits of limestone and concrete put on there over the subsequent 3-4 decades. I personally had two lorry loads of stone put on that side. Approx half is over an existing estd. 100mm concrete slab. Elements (and budget): 1 - Basic building. A SiPs kit from Simply SIPS, which gives an insulated 8x12' kiosk faced with OSB3, with a 5ft wide doorway for £1335. 97mm SiPs with U value of 0.3. Thicker panels not required as it is not designed for full day occupation in winter. Need to fetch it from Spalding - allow £100. 2 - Doorway. I will pay between about £600 and £800 for a custom made and fitted PVCu door and glass side panel to a pair of French doors for that gap, including locks and fitting, with a U-value of 1.5 or so. 3 - Base. Either 2" concrete slabs - £1 per square foot = £100, or 2" concrete slabs on Adjustable Support Pads which will allow me to adjust things after it is built if anything moves by changing the heights. 25 support pads ~ £100. 4 - Rainscreen Cladding. Box section plastisol coated corrugated at £10 per sqm including overlaps. Area required for walls ~ 25sqm => £250. Trims and special screws and things add £100 => £350. 5 - If I choose to batten out the corrugated for air circulation then approx 50 CLS length at £1.80 each => £90 plus £10 for bits and pieces ~ £100. Or 125m of roofing lath 30p per metre ~ £50. May be a better option as this is tanalised. 6 - Roof. It comes with a 1:40 fall towards the back. EDPM membrane. Say £150 including adhesive and trims etc. 7 - Captain Belt 'n' Braces may suggest a breathable membrane round the walls under the battens. 25sqm => not very much to buy. So for the groundworks and the building we are now at £2750 or so. In addition and not included: 8 - Electricity supply requiring FCU and switch in house, then about 2m of armoured cable, garage CU for lights, a ring main to power 3/4 double sockets, a small water heater, potentially a small fan heater for short periods, and a ventilation fan. Need a real electrician as it is for a rented house. 9 - A path down the side. 10 - A privacy fence across the front. 11 - 2 men approx 2 days to build it. 12 - I hope to build it such that it can be easily dismantled and relocated. The only fly I have in the ointment is, I think, that I need to watch the height carefully wrt permitted development. Ferdinand