Dunc

Roof on and fully functional. Windows in. Basecourse of blocks under the sole plate have been rendered. Only have breather membremane and battens on the walls; timber cladding not done yet. There is some damp at sole plate but I suspect this is water getting behind the breather membremane at windiw level (no cills yet so water puddling where the cill should be) and running down behind the membremane. No evidence of condensation or trickles of water down the radon membremane updstand though.

Hadn't thought of condensation! Although the upstand of radon membremane is dry to the touch. Obviously no idea what it was like overnight. No puddles outside.

I hope everyone survived the storm! We have some areas of slightly damp concrete around the edges of one room. Can anyone advise if this is a concern? Buildup is Mot1, radon barrier, 150mm reinforced concrete slab. (Eventually there will also be 200mm PIR, slip membremane, UFH pipes and 50mm screed.) I can only imagine that the radon barrier is compromised somewhere around these 2 walls. Only fix I can see is dig up the slab. Which isn't ideal 😞 Other ideas could be lay another dpm over the slab and tape to the existing upstand? Advice greatly appreciated.

Sounds like a similar situation to me: Timber frame on blocks. We've just had the blockwork rendered below DPC (well, after they finished I went around with a cold chisel and made damn sure ALL the render finished below DPC, not just "most" of it 🙄). Vertical timber cladding stood off the timber frame ~62mm will hang down ~50mm over the render. We're just leaving it natural colour. I'm concerned that as the render permanantly exposed to damp (wicking up from the ground) any paint may blister off with time...hopefully the render itself won't blister!

@JohnMo ~150m2. MBC passive kit, but not slab, so insulation and airtightness are passive-ish. Themal bridging not perfect though. Heat load calc from ufh supplier gives 4.7kW at -9. Plumber recommended the 8.5kW pump. Have to confess my calcs using the J. Harris spreadsheet give 1.7kW so there is a decent discrepancy.... If the 4.7kW value is correct then a 5kW pump would struggle to provide DHW in the depths of winter?

Well thanks for the recommendation to check MI @jack. Intreaguingly my installer was half- right. >=100mm from adjacent side walls but >=200 (or 300mm for the 5kW unit - why more for the smaller pump?) from a back wall (https://library.mitsubishielectric.co.uk/pdf/book/EcodanPUZ-WM50-60-85-112VH-AA_Installation_Manual_BH79D849H02UK#page-6-7). So it can sit in snug, but I think we'll bring it forward a good 500mm anyway. What I handn't realised until I read that, is that the big grill and fan are the outlet side of the pump. AFAICT warm air is drawn in the "back" of the unit. In my ignorance I assumed that was intake. So the ASHP exhaust air will be expelled outside the alcove area. Given we're in northern scotland and it's windy 99% of the time, especially in winter, I'm reassured that it'll mix with amient quite rapidly and the MVHR should be fine. I'd love to have had it modelled but as others have said, seems too complex to achieve. Fairly unconcerened about MVHR outlet condensate - it'll be minor compared to atmosphere most of the time (coz it's always raining up here )

Hi all, thanks for the thoughts! Lots to ponder. Just to try to address some of the thoughtful comments: Nothing is fully fixed in position yet but I need to cast the slab for the ASHP soon and the MVHR needs to be installed soon too (so it is a bit too late to make larger chages). The original ASHP position was architect driven and I suspect just because it looks tidy on the plan. ASHP ideally should stay on that elevation as the plant room with DHW cylinder and UFH manifold are just the other side of the wall so giving shortest pipe runs (as @Iceverge just hinted at). The ASHP can certainly move outwards from the alcove; my plumber/installer was the one who said minimum 100mm off all adjacent walls...I upped that to 200mm coz I'm paranoid. But sounds like others may feel more gap is better. Will check Mitsubishi instructions. Another option may be to rotate the ASHP 90 degrees? Bit ugly perhaps. Similarly MVHR box is in the same plant room so shortest runs for intake/exhaust pipes is into that alcove. That wall is single storey so intake can't move any further up. One proposal from CVC is to put the intake on the wall left of the alcove, same elevation. But really this only moves things ~900mm and introduces a world of pain installing through the garage/house dividing wall which of course must be fire resistant and airtight. And the timber claddign on the external wall of the garage is already in place . Interestingly CVC have only suggested moving the intake and don't seem to be concerned about the exhaust. The combigrille is interesting but if we are arguing the ASHP will move a lot of air around having intake and exhaust closer may increase rather than decrease the problem? lots to ponder!

There are several threads which discuss the loation of MVHR intake and exhaust ducts relative to eachother and/or ASHPs but I haven't found an example of a case similar to mine so would appreciate advice: The ASHP and proposed MVHR intake/exhause are set in a small alcove, about 600mm deep. The ASHP will be stood off both walls at least 200mm. MVHR intake is proposed at ~2000mm above ground level, so about 1000mm above the ASHP. Any risk that the ASHP could create a cold microclimate due to the alcove whcih would adversely affect the MVHR?

Just installing ours right now. Envirograf CV strip significantly less expensive than the Tenmat offering. Got ours from www.lifelinefireprevention.com Probably worth checking with BCO exactly what they would want to see; the regs are pretty general and your individual building may not need "everything".

I bought Boss, but second hand from these guys: https://www.jeescaffoldtowers.co.uk/ A bit cheaper than Lewis new and way less than new Boss. Website isn't great, but the guys on the phone were excellent to deal with and the kit, while clearly used (i.e. covered in paint and plaster splashes) appears good and solid.

I think it's quite common to do this joinery first, but we haven't. Just need to make sure all the levels and overhangs are set correctly so that the roof covering drains in to the future gutter location, barge boards are covered by the overhang, etc. And that there is reasonably access under overhangs to be able to place fixings appropriately

I hope someone can enlighten me on the need or otherwise for pumps in a wet UFH system with ASHP. Does each manifold require a pump? Is this in addition to or instead of the ASHP's own circultion pump? If in addition, how is this set up in the @JohnMo style using just flow/return temps to contorl the heat delivery with no thermostats to put a call on each manifold pump? If not, what parameters do I need to check to make sure the ASHP pump is up to the task. If specifics are useful: I have 1 manifold on each of GF and FF (lets keep any discussion of need for upstairs heating for another thread!). GF is 10 port supplying circuits of 40-100m lenght. FF is 6 port supplying circuits of 23-78m length. ASHP 6kW Mitsubishi. thanks.

Required in the void between the breather membrane of the timber frame and the external timber cladding where there must be a ventillation gap but also fire control. Vertically can be solid timber as no need for sideways ventillation however horizontally need to allow air flow but have fire stopping at first floor level, eaves and above/below windows/doors. Apologies to @kelvin for thread drift; back to the very impressive chicken housing 😉

@Kelvin can I ask what you did re: intumescent fire barriers behind your timber cladding? (sorry I can't find a previous thread you commented on) I'm guessing you put intumescent strip around at FF level and above and below windows. Anywhere else? Anything at foundation or eaves level?

thanks @JamesP so you took the DMP up behind the external insulation? No option on dropping the medite vent board - that's how it came from the factory. I might be able to put a fillet over the sole plate, but that's a lot of mucking about if it's not going to do anything beneficial. Option A: bring the breather membrane down to render level & ahere it (and the dpm?) to the render. Cladding over the top. Unsure what adhesive might work. If adhesive fails sole plate could become exposed to splash. Option B: take the DMP up behind the breather membrane. Breather membrane cut off at render level. If breather membrane fails or there is condensation behind it, this could run behind the dpm and affect the sole plate. But with the DMP lapped upwards, no risk of splash of the sole plate. In both cases unless I put a fillet of something over the sole plate, the membranes will have a bit (38x12mm) of free space to flap in.

Yes, photo is current condition: dpm under sole plate. Flap of breather membremane above. So if I cut the dpm fush, the breather membremane can flap over the sole plate. Maybe taped to the render?

So you'd just leave the sole plate exposed, other than the cladding?

Can anyone advise on how to tidy up the membranes at sole plate level on a timber frame? I will have a 10mm render applied to the block work under the sole plate. DPC & radon barrier flapping over this. Breather membrane covers the external board (Medite Vent board) of the timber frame. This external board overhangs the sole plate by it's own thickness (12.5mm). Architect suggested folding DPC up under the breather membrane then bringing the breather membrane behind the render to tie it down. Feels like a mechanism to allow water between the blockwork and render? Any risks with folding the DPC upwards? Frame will be timber clad with vertical counder battens then horizontal battens. Obviously the vertical battens will pin the breather membrane at the bottom of the external board, but not to the sole plate, unless I pack that out...wondering if that might be a good idea? any advice greatly appreciated

Wow! You seem to have dealt with a very very difficult situation calmly and extremely rapidly! Chapeau! Puts my stresses over having to get my window fitters back for a day's worth of snagging into a stark perspective - which is very helpful for me. So thank you, and best of luck!

Anyone able to help with this? Thanks.

I have a 45° pitch box profile metal roof which will intersect an EDPM-covered flat roof. The metal roof will be supported on 25x50mm counter battens and battens (to provide ventilation) on top of sarking boards. The EDPM laps up the sarking a good 500mm and my roofing membremane on the sarking laps onto this. To avoid screwing through the EDPM too low, how far up can I set the battens? i.e. how long can the unsupported end of the box profile sheet be? I can't find anything in manufacturer installation guides.

We're mid-build with MBC. They were the most expensive but the guaranteed airtightness was a big plus in my mind. However, the "integrated offering" of insulated raft, frame, and windows turned out not to be possible for us in the end. Early interaction with sales was very positive. The erection team were astounding to watch. Swift, without being rushed, and appear to be very competent. They should be having been at it for decades! It's not been completely smooth sailing. Communication with the design team had some slow patches (I suspect they were working at full capacity when we were in that phase). There were some areas of overlap between architect, SE and TF company which no-one seemed to really want to own. I had to push rather hard on a couple of things. There have been two structural/production errors that I identified post-erection. The measure of a good company is how they deal with these. So far solutions have been proposed with no wriggling or excuses, just a clear solution and timeline, which is as good as I could hope for. Overall, happy and would recommend. But for ANY company you go with, make sure either you are all over every little detail at every moment. It's astounding what "slips through the cracks" particularly during the design and engineering phase.

they are concrete bars which raise the reinforcing mesh to the required height within the poured slab. Yes, they just stay put in the slab.

That's the slab you can see there. There will be 220mm PIR on top then screed with UFH. Now that the timber frame company has left and it's just me and the Mrs, the build is progressing at glacial pace...slating is very very slow when you don't really know what you're doing 😆

No battens - this is nailed direct to sarking, as appears to be normal practice in Scotland.