cheekmonkey

@SarahHutch it was essentially a traditional slab style make up, blockwork perimeter with stick on 150mm perimeter insulation strip that also acts as expansion & limits thermal bridge. Slab make up was 100mm rejects / sand / membrane / 150mm insulation / slip membrane / mesh on 40mm feet with UFH tied to it / 150mm concrete i looked at some of the pre-formed systems but they were so expensive & didnt really work so well for fixing the SIP down do, whereas with this system our sole plate is bolted down to the blockwork.

Sorry missed your comment. I'll be honest I'm not sure what app was done when solar was installed but there was never a mention of costs until after the event. I simply don't agree with SSE and their rationale the legislation talks about new connections which ours is not, its just a pv install. The network doesn't need upgrading at all. The only way out is for me to limit my export and reapply which just seems completely stupid logic as everyone looses. Still these things never seem to have any common sense applied

I call polished when it's ground back and polished whereas ours is just floated. Agree on reason to fill cracks but our robot hoovers every day 🤣. It's purely a design detail we like regardless of practicality

No not yet. Osmo do an oil but its quite a faff to do now we've moved in. It's marked a bit in kitchen area from drops of grease but it doesn't really show due to the nature of the natural imperfections in the finish

We've recently done something similar. 150mm powerfloated finish (Not polished - i'm not sure why you would?) mesh in bottom 40-50mm with UFH pipes tied to the mesh. so circa 100mm on top but some places a touch less where levels werent perfect. we have saw cuts made throughout the slab the following day circa 30mm deep, crisscorssing the whole building. we have chosen not to mastic them as quite like them, but have mastic sealed other places as we have the old concrete barn protuding through the floor. most builds probably wouldnt have as many cuts but with the fixed structure with 8 posts we felt safer to cut to each to allow it to crack in all directions we have only got one major crack not down the cut line which is right down our hallway but i think probably due to the hot water supply to the other end of the house running under that bit. although that's even under the mesh at the bottom it must have had an impact

My advice is don't over think it. You're on the right lines. We didn't use Kingspan, we used a system from SBS via our installer NewForest SIP, but have 170 walls & 200 roof. Essentially same as your make up here but only have internal void if req. I deliberately designed service runs to avoid battening all the internal walls so just picked a few. ultimately to just save time & money & also have walls i can fix things direct to OSB like kitchen units. We also have batten & counter externally with 20mm half lap larch over glidevale membrane We didnt bother with vapour barrier or any special taping, i did externally tape the glidevale membrane with their recommended tape but TBH i think it was probably a waste of time. all panel joints were foamed on install & mastic around roof joint. we've achieved an air test of 2.56 (that's even with 14m of leaky sliding doors), an epc of A & the place is toasty warm with no heating on at all. it's very stable temperature, we also have MVHR.

I've had a recent letter from SSEN who state that I'm due to pay 2nd comer charges under ECCR after my recent POV install. (Circa £2.5k fee) When I called & dug into it they said it's because I am exporting & have an 8kw system & whomever put the supply to our & neighbouring plots (It's a barn conversion & the 3 plots had a new supply installed to sell them) are owed a slice of their costs of the install. I stated it's not a new connection as we've been here 18mths, the person who installed the supply never actually connected so we're not really 2nd comers, our neighbours who have about 20kw haven't been charged & so ECR shouldn't be due but they are adamant as I'm "changing the utilisation of the service " I have to pay the fee. I've argued until I'm blue but the only thing they suggest is that I complete a G98 & limit my export to 3.6kw which will avoid the fee. I find the whole thing a bit of a joke as surely the export benefits everyone & there's no network re-enforcement required. the pay back on the pittance you get would take years to clear. Just wondering if anyone else has experienced this at all - it really feels like a mistake but trying to make sense of the legislation isn't really my area of expertise.

We're 5% on supply & fit as we're change of use from Agri to Resi. I'll be using the same contractor to fit: - Solar - Heat pump - Underfloor heating (from heat pump) - General Plumbing (1st & 2nd Fix) Am i right that 'renewables' are 0% VAT regardless but which bits fall into that? Do we need to break up the heat pump & underfloor from the 1st fix hot water etc? Does MVHR also fall into 0% VAT? (different contractor) Thanks in advance

i'd deffo double check the regs on DPC to outside ground level to be sure, our way around this is to bring block to finished floor inside & DPC outside, then bolt soleplate through above that. We will also run a 25mm insulation upstand at least 150 up inside the sole plate & SIP wall to avoid any condensation. basically i think bring your block up 50mm more & DPM/DPC works & then add upstand internally

You shouldn't really need 100mm blinding, but otherwise seems the same as we're doing. depending if the floor goes in before or after the SIP you can 'double bag' with dpm - so we're going to dpm & wrap up inside the sip as floor goes in later & therefore the internal dpm wraps up the wall inside too. don't worry about the bolts through dpm/dpc. it's all out the ground anyway. can't quite see the dpc layer on screen but i believe that needs to be 150 above outside ground level, it's not clear but looks like it is lower

Vertical larch T&G cladding - what are the options for detailing external corners? I have only ever done horizonal before & just fixed nice corner posts & run to that but trying to think of options for when running vertical. Our boards will be something 75-95 with shadow gap (not 100% decided yet) Keen to hear any options & photos if possible TIA

Ahhh ok - i see what you are saying... ours does not carry the walls. I maybe didn't make that super clear. The perimeter SIP wall will be sat on block/brick on a strip footing, the slab is just a slab From my original comments : "my thought at the moment is: - strip foundations with block/brick stub walls that the SIP fixes to."

@George so why is the raft a must? Why not make the slab structural, insulated & have the heating all in one like my idea? That way you have a nice mass to heat like Matt had experienced & ultimately a slightly easier construction as less process.

@mattman thank you very much for the detailed reply. I'm trying to get a all with the engineer today but i've spent a couple of days head scratching & drawing up a layup which is very similar to something I built myself before on a TF building (so really little difference to SIP). Interesting to hear you would try & incorporate to one slab if you did it again - that's what i'm trying to do else you end up with soooo much concrete for a really lightweight build! I've worked out that the floor has to go down before the SIP really as the DPM layer would have to be laid & ultimately would get trashed no doubt. There are risks of damage to floor so we will have to board over it but it definitely makes the concrete guys job easier as they would float an open slab. (have to pray for good weather but the last one i did myself i did in October & managed a reasonable finish to the power floating.) My plan/proposal for engineer is: 150mm crushed sand blinding DPM 150mm insulation slip DPM 50mm meshspacers mesh UFH clipped to mesh 150mm concrete powerfloated We'll see what he says. Really pleased to hear about the UFH experience you have too. We have circa 210m2 floor (plus integral garage but wont heat that) & expect we'll have a similar size heat pump to you for DHW & UFH probably jsut split into 2 zones for bedrooms & rest of house & probably similar size solar set up with batteries. We're used to living in old houses & think we might find the house quite warm without heating on. We will have MVHR also & a log burner just because we love the atmosphere & warmth from them. We're also going larch cladding, basically we're copying you . I was looking at standing seam roofing but our budget is already looking stretched & I might end up going metal sheet profile instead as I can fit that easily with some labour help. I pushed the button on the SIP build yesterday so that will work into slab detail & starting to dig some holes over the next month or so. I must start a progress post somewhere to stick up some photos Thanks again, great to hear such a positive experience.

@mattman i was about to post something later in foundations forum. we want a power floated concrete finish floor in our barn conversion but struggling to work out the slab make up that best works. we have a SIP build around an old concrete frame barn but it has a fair bit of proposed new steel work to hold it up. We have proposed ASHP & underfloor heating (single story apart from small mezz) architect had originally conceived a raft foundation but they expected us to screen the top therefore 75mm - talking to concrete people they say the top coat needs to be more like 150mm. they then said that they dont think that would work with UFH. my thought at the moment is: - strip foundations with block/brick stub walls that the SIP fixes to. (including internal walls) The steels bolt to these walls also, or small concrete pads - slab make up is then hardcode/sand/membrane/insulation/steel mesh/UFH (on top of mesh to in top part of slab)/150mm concrete that's power floated. All this can happen after the SIP is built so in the dry & won't get damaged after No-one seems to want to help advise what's best so i'm at the point to making the choices myself. Interested to get your experience on this & if you followed a similar make up at all. TIA Pete