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Thank you. Keep bays as square as possible, ideally 1:1 to 1:1.5 and no worse than 1:2. UFH pipes stapled to insulation are common and fine, but they do not control cracking. Saw-cut joints to about one-third depth and cut early so the slab cracks where you want it to. Avoid adding water on site, over-trowelling or closing the surface too early, delaying saw cuts, skipping curing, or pouring long thin bays. Get the joint layout, timing, and curing right and the UFH will cope with normal movement without issue. You could use a macro fibre but it will not fix the basics. Used correctly, they are a support measure, not a solution.

I have spent decades working across ready-mix, precast, materials testing, failure investigation, and standards compliance, gaining hard-earned experience that comes only from solving real problems on live projects under commercial and regulatory pressure. Locally plots seem just to appear on planning, planning is rejected then a forsale sign appears on the plot. I am either searching in the wrong places or just late to the party.

Thanks guys. Would you advise doing the pointing before spring if there is X days / hours of dry weather forecasted? How many hours/days would you recommend? How much mortar do I need to rake out and refill? If you could point me in the direction of a useful guide or video that highlights best practice that would be appreciated. Thanks again

Will grab some better ones tomorrow but here’s a hastily cropped and zoomed version. The buildup on top of this includes Actis BoostR Hybrid - for insulation and airtightness. So ideally the DPM gets lapped up, taped, BoostR stapled and taped, battened, and then clad / render depending on area.

The entire brick facade (either side of the bay and above) are as one. That’s how the upstairs brickwork is defying gravity. The first floor joist probably carry on and protrude out through gaps in the brickwork, like fingers, which forms the structure that makes the canopy. Other option is that there’s just a timber framework fixed to the brickwork, like a tent frame, and the downstairs bay forms some of the structural strength. A lot of these types of arrangements often used hardwood window frames to bear loads, and then they got cut out and replaced with uPVC, and then these show signs of failure associated with weight bearing on them (which they can’t cope with).

To wrap this up……. ”No” 👎

Have you got some pics of the ‘affected’ areas? Lapping it up may harbour water so we need context for some better answers

Percy-verance. Lol. Gotcha. 😉.

Hello everyone. I’m doing a few ‘keep busy’ jobs over the next week until my crew are back on site. One of them is tidying up the DPM flaps that are hanging everywhere. My build is timber frame, over blocks on slab. DPM is between blocks and soleplate as per usual - and currently extends out anywhere from 15cm to 40cm. What should I do with this? Original idea was to lap it up the breather membrane on the OSB (DPM flaps cut to a uniform length first) and then tape. Is that just the standard detail?

Im not sure I agree with your interpretation of the thermal imaging. That pattern could definitely be consistent with ground-contact brickwork below bridging cold up. Do you think then that this isn’t the culprit and it’s the frame threshold? Ie a manufacturer issue?

Why make life difficult for yourself. Just do normal, why reinvent the wheel? Future proof is normal stuff, not novel. Leave DC to cars and and small boats.

Me too. Big time. I’ll take and post some pics tomorrow but you really should get out more lol She has served, and hopefully will continue to serve, with distinction. Bless her. I’ve become quite attached.

I've started to do something similar. Found down to about 5 degs normal WC is just fine. But once I get into defrost mode, battery takes a bit of a pounding, especially with a couple of days sub-zero. So set the WC curve to stop at 5 degs, my old UFH controller has an outside temperature reference. So use it as a cheap rate boost controller, so when its 5 degs and below outside and below 20.5 inside, it activates a second set point for the ASHP and allows a higher boost flow temp, for cosy cheap slots. Rest of the time the ASHP ticks away at a low flow temp. Use the same amount of energy, get similar CoP, but moves the majority of the energy usage to the cheaper time slots.

I agree that installers are not expected to redesign an entire building, and I’m not suggesting they should. Where I differ is that the interaction between a supplied product and the existing building fabric is part of the installation outcome, particularly where that interaction creates an internal surface that repeatedly drops below dew point under normal conditions. The difficulty with the tyre analogy is that in this case the installer didn’t just “fit tyres to an unknown suspension”. They surveyed the opening, specified the product, chose the threshold detail, and installed it. I didn’t instruct a brick-to-brick threshold or ask for zero clearance beneath the sill - that detail arose from the way the installation was measured and executed. On the thermal imaging point: if the brickwork were thermally bridging up the frame as the primary mechanism, I’d expect a more diffuse vertical gradient extending into the room and along the uprights. What’s actually observed is a consistent cold band at the sill/frame junction with intensified cold signatures at frame junctions, which correlates with where condensation and mould are forming. That pattern points to the threshold/support detail being a significant contributor, not just the general floor construction. I’m not asserting fault by default - I’m trying to establish whether the outcome is an unavoidable consequence of the existing building fabric, or whether the threshold detailing has unnecessarily amplified the cold surface at that junction. That distinction matters, and it’s why I’m seeking independent review rather than relying on analogies or assumptions.

PS. Regardless of economy polystyrene is so nice and easy to work with - the spring in it means you can easily get it really tight - for me that makes it worth serious consideration. PIR May have a better lambda but the better fit of polystyrene must compensate a bit methinks.

Good question - the condensation and mould are localised, not distributed across all frame members. They occur at: the internal sill / lower frame junction, and the lower portions of the vertical frame members where they meet the sill, particularly at the junctions between the main door frame and the side panel frame. They are not present: higher up the verticals, across the mid or upper horizontal members, or elsewhere in the room under the same conditions. Thermal imaging shows a consistent cold band along the internal face of the lower frame/sill junction, with a sharper cold signature at the side-panel–to–main-frame junctions. That correlates exactly with where condensation and mould are forming. That’s why I’ve been focusing on the threshold detail rather than the frame sections generally. If the frame profiles themselves were underperforming thermally, I’d expect condensation higher up the uprights and more uniformly across the frame, which isn’t what’s being observed. On reinforcement: I haven’t opened the frame to confirm, but given the door size I would expect steel reinforcement at corners/uprights, as is typical. That said, the condensation pattern doesn’t suggest a corner-only or reinforcement-only issue - it aligns much more closely with the sill/support interface and local thermal continuity at that junction. I agree that the floor/threshold interface is likely playing a role in cooling the lower frame below dew point; the question I’m trying to resolve is whether the way the sill is supported and detailed has unnecessarily amplified that effect, given the resulting persistent condensation and mould.

I was dead set on 250mm of polystyrene with the DPM effectively sandwiched in the middle. Our slab however came up higher than planned so we ended up with 240mm of space so we converted to a PIR layer atop the polystyrene. I sort of priced various options using online prices and almost ended up designing by spreadsheet. Then I talked to my favourite building supplies bunch. A few mildly confused emails led to a clarifying phone call and it being pointed out that if I used 120mm of both then stocks are held locally and a good price could be had. Suddenly it got easier. We got prices matching or beating the best I could find online. So given my experience I’d have a coffee with the most helpful local dudes and see what they suggest. I would not contemplate a step in the DPM. I’d put a flat layer of polystyrene down then the DPM then vary the above later. I found to get good straight cuts in PIR I had to saw and 120mm is not much more nasty than 50mm. Both I found horrible. But I did notice that when the foil face became detached the sheets were much weaker and had to be handled more carefully. I suspect one gets less horrid dust with foil faces too.

The installer is not responsible for the installation outcome in so far as its interaction with your existing building fabric. They are responsible for installing the door correctly - not for correcting or redesigning a thermally poor threshold detail that pre-exists the installation. Their response doesn’t seem great from a customer service perspective and as others have said they are responsible for foaming, sealing etc in so far as it relates to installation of their product. This will improve things for you no doubt. However, Unfortunately I think your camera shows the brickwork thermally bridging UP (not across the threshold which would imply no thermal break in the frame)… it’s a bit like fitting new tyres to your car.. you’d expect the fitter to balance your tyres and get the pressures right. But if your suspensions fundamentally out and the car pulls to the left: whilst it’s not the ‘installation outcome’ you’d like, It’s not the tyre fitters fault what they’re fitting onto isn’t fit for purpose..

On my system am I pushing the weather comp curve down a few degrees (ie applying a setback to flow temperature, not room temperature) during peak: https://www.earth.org.uk/heat-pump-16WW-control.html#current I am actually on a flat tariff, but I did think about how I might make this work saving cash and carbon with Cosy: https://www.earth.org.uk/heat-pump-16WW-control.html#Cosy For our old gas combi I did indeed have the space heating entirely off for 4pm to 7pm.

OP, forgive me if I have missed this, but where do you see the mould and condensation? Is it on the main frame members (perhaps the bottom of the uprights and on all of the horizontal members) or perhaps only at the very bottom of the bottom members? The former could suggest that the specific frame sections are much less well-insulated than many of us thought* and the latter that it's perhaps the cold floor cooling the frame and taking it below the dew-point, in which case replacing the course of bricks immediately below the cill with Compacfoam could arguably warm things up enough to address (I hesitate to say 'cure' as we do not know enough about the specifics) the worst 'manifestations'. *Do they still use galv steel reinforcement at the corners of bigger frames?

Then he’s talking nonsense. You always insulate all around the frame and that includes the threshold when necessary. It doesn’t need to be foam, Compriband would be good enough.

There are no benefits or advantages in DC light systems in a residential property. LEDs might be DC, but the drivers and controllers are relatively cheap, reliable and available. Overall I2R losses make it inefficient.

Your wish etc, fire up the X1C man! https://www.thingiverse.com/thing:4274516

I don’t think I’m missing that point - I agree that uPVC frames are inherently more insulating due to their chambered design, and I’m not alleging a defective product. My concern has always been about the installation outcome, specifically at the threshold detail. Where I differ is that I’ve already tried to resolve this reasonably and practically with the installer. The installing team have attended multiple times, and the company owner himself has visited. On those visits, the issue was repeatedly dismissed as “normal” on the basis that heat rises, that the bottom of doors is always colder, and that condensation is caused by breathing or clothes drying indoors - which I made clear we do not do. Beyond additional sealant, no attempt was made to investigate or improve the threshold detail. I’m not disputing that installing onto outer brickwork is common practice in typical UK builds. I am questioning whether, in this specific case, the resulting internal surface temperature at the sill/frame junction - which is cold enough to repeatedly condense and grow mould under normal occupied conditions - is an acceptable outcome of reasonable care and skill. If insulating under the threshold is the appropriate mitigation, that’s exactly the sort of conclusion I was hoping to reach collaboratively. Unfortunately, that option was explicitly ruled out by the installer, who stated insulation under the sill is not required and that nothing further could be done. Given that, it seems reasonable to seek independent or regulatory review rather than continue a circular discussion where the issue is acknowledged in practice but dismissed in principle.

My advice is to take on board whatever @craig suggests. Unless your agreement with the installer included improving building fabric to mitigate existing cold-bridging, then you only have some minor snagging issues that you could probably have resolved yourself with some expanding foam and sealant in the time taken to craft your comprehensive and eloquent posts!