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I suspect that perimeter strip would do more good than the Thermalites. Look up the u value's. I would do both. Your XPS detail is same as I had originally specified. I let my builder convince me to drop the cavity tray and blown EPS to the bottom of the cavity. Seemed reasonable at the time, but what I hadn't anticipated was how much the cavities would get filled with dropped mortar. No matter how many times I asked them to be careful... With hindsight a cavity tray would have caught the droppings which the brickies would have had to somehow clean out. Maybe that was their real reason to suggest no XPS and tray...

Given the choice between 50mm push fit and 40mm solvent weld, what would be preferable?

Up to 4m. Could use 40mm for most of it, just want to do a gd a job as possible.

The four biggest builders merchants don't, and a couple of the larger plumbing suppliers don't either. Mustn't be what's done round these parts...

Hi folks From browsing this forum it's fairly clear that for waste pipes buried in the floor and in ceiling voids 50mm solvent weld is the way to go. However, I am seriously struggling to source any solvent weld pipe an fittings in NI (exception being screwfix abs pipe, some of which is described as overflow pipe, and a little pricey and limited in fittings available). All the local places only carry push fit, and mainland GB supplier don't want to know. Just spent some time putting in a large order with Plastics Express only for them to then cancel it 2 days later saying that they can not send out items longer than 2m! So, at least I can get the fittings, but not the pipe. Now starting to wonder if push fit would be ok, there's going to be some buried in insulation under the screed, and in service voids under pre-cast slabs. Thoughts?

But of a risk of plaster board screws missing the batten and going into the cable?

I spoke to the electrician that the builder wants to use yesterday. He's never done a job with a 25mm service void, and didn't know what I was on about when I tried to explain that we want passivhaus level of insulation and air tightness... So, can anyone recommend an electrician in NI? Also, what is the best method of hanging wires in a void under vcl anyway?

I think most of the lights mentioned in this thread are deeper than or need a clearance than means a 25mm void is insufficient. So yes, making a pocket in the pir is an option, but if the vcl is between the void and the pir that means a cut out in the vcl and too and somehow sealing up. I know you can get plastic mouldings to help with this, but wouldn't it be easier to have the vcl on the other side of the pie?

Yes, tho I was more concerned about having to penetrate the vcl at each light if it sits more than 25mm back.

That all makes sense. Only thing I'm thinking is if the VCL is between the battens and 60mm then fitting recessed led lights might be tricky. I was otherwise planning on cutting a disc out of the 60mm PIR where there are lights so that's there's a localised 85mm void. A v slight comprises on the insulation, but overall a tiny %.

Hi all Part of our roof make up is to be, from inside: plaster, plasterboard, 25mm service void (25mm battens) 60mm PIR, air tightness membrane, rafters with 125mm PIR between. Builder questioned this as the air tightness membrane will be punctuated in multiple places by the fasteners that hold on the battens, 60mm PIR and the membrane itself. Is this a fair point or will it all be ok as the screws/nails self seal the holes they make? Thanks

Hi folks Our first floor is pre cast hollow core which will have a screen over it, no UFH. My understanding is the purpose of the screed is purely to provide a level floor surface, particularly as the slabs are supplied slightly convex. Is there any recommended minimum thickness other than enough to creat a flat surface? Builder wants to put down nominal 50mm, but I think we can get away with much less. Want to keep it thin to scrape back a few mil of ceiling height. Thanks

Just to add, the brickie had already built the blockwork and left out the pumice bits (who knows why...). Suggestions was made to fit twin wall stainless flue inside the blockwork, but I'm not convinced this would be a good idea. Poor access and I don't think would meet regs.

Hi folks. This is the intended detail for how the twin wall from wood stove feeds into the more traditional chimney. All signed off by building control. However, builders have suggested bringing the pumice out at 45 Deg into the attic space. Seemed like gd idea to me, easier to attach the twin wall to, or at v least better access. What do we think?

So, I spoke to the roofing sub contractor, who uses Proctor Roofsheild which is a breathable membrane which will be fitted with no sofit vents. So in effect giving a slightly ventilated cold roof, in as much as the ventilation is through the membrane. He also insists the counter battens are not needed.

I've been wondering about this too, specifically whether 'underground' pipe and fittings can be used above ground if boxed in. Much cheaper and more fitting options (and I have a few spare bits) being my reasoning. I would imagine that the above ground stuff has additives to minimise uv degradation, but that would hardly matter for a boxed in installation. Decided to phone our local building control office (in NI) today to see what they though, they said no particular reason to not use underground parts if boxed in.

Thanks for the replies. Enough to convince me to counter batten. Perhaps in the vid (which I'll watch this eve), what is the best detail for taping the membrane at its lower edge? Does the membrane not needed to somehow dispense any water into the gutter, but needs to seal to the inner leaf of the cavity wall?

As much out of curiosity, whats the difference between a solar and a heat pump tank, that accounts for £521 difference in price? Both are 500l, the cheaper has 2 coils https://www.cylinders2go.co.uk/shop/renewable-energy/telford-tempest-500-litre-twin-coil-solar-indirect-unvented-cylinder/ https://www.cylinders2go.co.uk/shop/renewable-energy/500-litre-telford-tempest-heat-pump-cylinder-twin-immersion/

Our drawings states that the whole slate covered roof should be battened and counter battened. This was the advice from an architect friend as best practice. However, the builder has announced that he only intends to counter batten the warm roof sections as there's no need for the cold roof parts. What are the thoughts on this? Should i insist on counter batons everywhere, over both cold and warm roofs? Thanks.

"Is that a timber frame above ground level? Looks like very thick walls" It's block cavity walls, with 240mm cavity. Yes, nice and thick.

This what I intend. Our cavities only go two courses below the floor level so not really much to build up. The 100mm of structural insulation below the door will be foamglas.

Everyday's a school day. Perfect, thank you.

Just got some decking planks to make steps for the static caravan. There's course grooves on one side, fine protruding ridges on the other. Wondering which way up to put them? Don't care about asthetics, just concerned about grip, esp in damp winter conditions. Thanks

Thanks markc. Yes bottom chord is 138mm wide so good bearing area. I'll see what steel plate I have about the place, think there's some 6mm I could use.

They're getting paid fixed price so I'm not paying by the block, thankfully. And, there was quite a bit of rework that produced a lot of waste (builder's mistake) as a couple of walls were redone. So a lot of what you see has mortar on it.