amin

Coming up 400mm from the joists was partly because it feels like I’m doubling up on VCL with the foil face of the PIR which I would want to tape up - I’ve assumed that provides a good layer of airtightness still? On the counter battens you’re right to point out the counter battens issue - at 25-38mm it will definitely be a build up. But this in my view will barely be noticeable from street level vs adding insulation layers on top? On solitex it’s a diffusion open membrane so venting above should be allowed - I’ve stuck to the pro-Clima product given the intello membrane inside. Sounds like there no way round getting a/t membrane in will just be a PITA and no shortcuts I’ve got the house back to brick so have flexibility on the room below. @Redbeard how would you approach it if you were to design it?

Not sure if this is the right place to post, but I’ll start here. I’m rebuilding my roof as part of a loft conversion and also installing MVHR, so I want to make the roof as airtight as possible — ideally all the way from the eaves (where I’d like to run ducts between the eaves and dwarf walls). It’s a solid brick Edwardian house. Also in a conservation area so can’t do a warm roof due to the build-up and have to preserve what it currently looks like. My planned build-up is full-fill mineral wool between rafters, with PIR insulation underneath. What I’m struggling with is where the airtight layer/membrane should go, and how to detail it around all the penetrations from rafters, joists and the joining it back down to the wall from the room below. What’s the best approach here? I feel like it’s a huge puzzle piece trying to get that membrane in and I must be missing something simple here. I’ve attached a detail of what I’m aiming for (apologies for the rough SketchUp drawing!) mineral wool roof.pdf

The internal wall I may have to rebuild parts anyway because of supports I need for some steels that are going in - so dropping that wall may be on the cards regardless. Worst case I can tie the joists to the timber on the other side which is still intact. On the external wall side the joists just sat in the well pockets. Joists have a 250m void below with 100mm joists.

My worry with taking out the wall plate is just how much of it there is and just not being able to take parts of it out. EPS beads is one I haven’t come across. How would that work with the wall plate where it is - that would still end up being on the cold side?

I’m looking into replacing the original timber suspended floor in my Edwardian house with a solid floor - to support UFH and also insulate it better. While lifting the floorboards, I’ve found timber wall plates embedded in both the external and internal walls - these support the joists and sit just above a slate DPC. To move to a solid floor, I’d need to remove these wall plates throughout the house otherwise they'd end up in the build up without ventilation. Has anyone tackled this before? Is it realistically doable - or not worth the hassle?

I’m doing a loft conversion and adding a flat roof infill as part of that. Due to head height issues, I can’t go for a warm roof, and I want to avoid the issues of cold roof ventilation and PIR fitting between joists. The Siga “compact roof” and Partel unventilated roof systems seem promising as space saving, insulation-between-and-over solutions. They also seem to avoid the need for ventilation and allow for continuous insulation. I’ve attached some images of the build up. Has anyone built this type of roof? If so a few questions for anyone with experience: - What products have you used for the intermediate waterproofing layer shown in these types of diagrams? - Are there any practical issues I should be aware of when building this type of roof? - Is there a reason this roof type doesn’t seem to be commonly used?