Search the Community

Just getting my plumbing done and noticed ( after it was done) that the 22mm copper vent pipe to my unvented DHW cylinder is a “ hole” in my airtight house. I suppose I could create a trap by using lots of 90’ bends but even if I filled it with water it would eventually dry up as no water passes through it regularly ( I hope?). Any good ideas out there?.

I get that masonry wall floor joist hangers are favoured over traditional in-wall fixing of joists in the pursuit of airtight homes but can these hangers cope with 100 years of cyclical loading? Here is my beef. Driving a metal nail into a brittle masonry block to attach a hanger feels like an abuse of such dissimilar materials with long-term failure designed into the fixing. Next add 100 years of 80kg cyclical loading as humans walk around inside the home, stir in some thermal expansion and contraction loads on the hanger attachments and surely after a decade or two the hanger nails will start wobbling in the blocks? Then finally for a laugh apply that process to light thermal blocks. Are my concerns unfounded? The no nonsense commercial builder of a plot nearby has fitted his metal web floor joists direct into the inner blockwork and these blocks are heavy structural blocks I think.

That's the thing about building a house; there are too many choices. And I'm at the bottom of yet another really steep learning curve. Hence this post. We need to render the internal space between the ceiling and first floor to make sure this area is airtight before we fit the POSIs. At this stage in our decision making process, I usually turn to the online version of SPONS and look at what's available. Comprehensive though the section on rendering is, there's no mention of rendering to provide simple air-tightness. For this small section, the look of the render and surface finish is irrelevant, and thickness is only important in so far as air-tightness is concerned. Waterproofing isn't relevant. I've come to understand that this process, however humble it may be, is key to keeping our future living cost down. So it's important to get it right. Could you just give me some starters to help me widen my research, please? So far I have Looked through SPONS for trade names and researched those that I found : Tyrolean Finish, Cement and sand, SIKA waterproof render, Sto External render, Armat Classic Basecoat, K-Rend. Done an internet search and come up with this interesting article: maybe we should simply render over an airtight membrane. Visited the GBF and read this article, but it's mainly about air-tightness tapes: it raises important issues though about finding plasterers who are keen on attention to detail. Knotty one that. Found out that there's stuff called undercoat plaster......... This hill is steeper than I thought. Ian