SBMS

@Dave Jones - would only one row (deep) of marmox across the cavity be required for a 186mm deep sliding door track? With your detail above most of the doors and track are bearing down on the PIR?

Hi @Dave Jones Is the below right? Detail 5 or Detail 6?

We also have a flush threshold - so our track is sitting so its flush with FFL/screed level (adjusted diagram below). You've got me thinking.. Is the majority of the thermal bridging from the 'back' of the door track, and would the following detail - which is a variation of detail 1, help reduce that bridging - effectively reduce the cavity to the known bearing width of the door track and then do detail 1 with a PIR upstand adjacent to the screed: I don't know where the majority of the bridging would occur.. obviously the track would still suck up heat from the concrete, but would transmission be limited with the PIR behind??

Detail 3? With the marmox blocks on top?

Thanks @JohnMo - got it. My challenge is that I need 150mm clear above the roof deck so will need to do a 150mm + 20mm compacfoam above, but that should be fine. The detail for my roof light needs a rebate in the compacfoam as below: This is where I am up to with my detailing: Two questions: 1. Does insulated plasterboard on the internal face of the aperture deal with my VCL as well, or would it be better to run the VCL up the face as well and then put regular plasterboard on? 2. Would GRP adhere to the outside face of the compacfoam, or would it need to have OSB screwed to it? Thanks Matt

Just detailing my fixed flat roof light upstand and following on from a conversation with @JohnMo (sorry for my persistent questioning John!). In that other thread John suggested a timber frame with compacfoam on top for the upstand. It's going to be made out of compacfoam for the upstand - the rooflight will sit on this. On a warm roof with 150mm PIR. Can I run the PIR right to the edge of the aperture, and then form a 150mm upstand on top of the PIR? Roof light will weigh about 250kg - Detail 1. Or do I need to do two layers of compacfoam as per detail 2?

Is this sufficient support for 9m of aluminium triple glazed sliding doors to sit on? The PIR/Screed won't cause undue deflection? Also, if building from scratch, can you not just finish the inner block at that height, rather than breaking it away?

I think this might have been done to death, very often with no good conclusions, but we've got a significant amount of door thresholds on our ground floor (quite a bit of glazing). I'm trying to solution the different options and have summarised three possible details (traditional brick and block with a 200mm cavity - blown EPS beads, not that that matters). Can anyone comment on whether any of these options are not recommended, or whether the additional effort/cost, say, of running marmox or compacfoam (Detail 3) outweighs the potential heat losses from thermal bridging? Does option 2 work (with the doors effectively bearing onto PIR and screed)? This is to allow bottom fixing and support for a 160mm triple track slider system, and also sitting into the cavity as much as possible.

I get you. Could I make the upstand out of two layers of 150mm compafoam instead of a timber frame?

@JohnMo this detail would be okay for non ground floor.. but on ground floor there won’t be cavity insulation under the door.. with a 200mm cavity and potentially a 160mm door track, what’s supporting the track over the cavity? Would you recommend a structural cavity closer? Or take the floor insulation and screed to the outer brick skin (dropping the inner block a course or so)? Is PIR and screed enough to carry the weight of the doors?

Thanks - and in between the studs of the timber upstands goes compafoam (my section view 1) or could I infill with the PIR?

@JohnMo thanks for this - am still a bit confused with the makeup.. Is it like the below (tried to show it from a few angles). So build a tinber frame around the aperture, then fill between studs with compafoam with levels as you mentioned?

Thanks @Onoff. He probably does have a mate, just wanted to make it as frictionless as possible. And if I can pay a few hundred quid to get it inspected by the BC at the end that’s nice and easy?

Also - is the compacfoam effectively infilling the frame around the top of the aperture?

I’ve often heard Sparky’s don’t like signing off others work - could this cause an issue finding someone or could we just get an EICR report from a third party as sign off?

Thanks! So it sounds like there is a mechanism for them to inspect. We will be using a private BC so will need to check with them

Would there not be thermal bridging that we are trying to avoid where the timber frame connects to the roof deck? is the roof light aperture to the left in your section diagram?

I wondered whether BCO would accept a third party EICR post completion, if they did ask?

It’s a possibility, I just wondered if there’s a possibility for BC to sign off.. if you were competent enough to do it yourself for example but weren’t able to self certify can BCO sign off?

Father in law is a retired electrician (retired last year) so no longer able to self certify. Was considering him doing the electrics on our self build. I know that another electrician can sign it off on their behalf (which is frowned upon). Is there a mechanism where building control will sign off the electrics without the need for self certification?

Do you mean build a frame that’s 100mm away from the aperture around the aperture. And then on the ‘outside’ of this frame the PIR butts up to it and the inside the compacfoam? struggling to visualise what you mean

Thanks @JohnMo got a video of it online. This looks like a great idea for our upstand. One problem is that we are doing warm roof construction so putting 165mm insulation on top. Compafoam looks like it’s max height is 150mm and I think regs state the upstanding needs to be 150 above the finish roof level. Would you do 150mm compafoam then a 165mm timber frame on top or two layers of compafoam to build a 315mm upstand?

Is the whole of the upstand made out of it? Have you got any pictures or details? cheers

Ah damn, now you’ve got me thinking of insulated up stands - never even realised this was a thing…

Anyone got any recommendations for a cost effective flat, fixed roof light for our flat roof that achieves 1.0 u value or lower? We need two and they are each 2800mm x1300mm.