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I'm thinking about the aggregate version of foam glass so this stuff which can be compacted. Also supposed to be good with moisture so DPM doesn't always seem to be necessary. Price wise I don't think theres much in it between them - the foam glass might be marginally more.

I'm refurbishing the floors on my Edwardian house. I've removed the old timber suspended floor and looking to put in an insulated floor with UFH. I have about a 350mm-400mm void and ideally don't want to dig to far below this. The original slate DPC is about 150mm below floor level. I have two options and wanted to validate what works: Option 1: Foam glass aggregate (bottom up): 250mm Foam Glass aggregate compacted 75mm Sand Cement Screed (with UFH) Total build up 325mm I'm considering option 1 because of the level of the DPC being below floor level and bridging it with any other options - but maybe i'm overthinking it? Option 2: 100mm Compacted Hardcore DPM lapped to wall and above screed 200mm EPS 75mm Sand Cement Screed (with UFH) Total build up 375mm Option 2 does it work without a concrete layer and is the hardcore enough? There are some posts on here that suggest concrete isn't required and the hardcore might be enough? Also what about the fact that the DPC might be bridged in this setup? Any advice and thoughts on these options will be appreciated!

Appreciate the ideas. Going behind the chimney up dormer sounds like the easiest way to comply - will there be an issue with the number of bends required by this? I won't have any other soil vent pipes, the neighbours definitely do have vent pipes. The AAV is an interesting one and would certainly look a lot better. The other thing I was thinking about was moving the vent pipe internally and going straight up to the right of the first floor toilet.

I’m looking for some advice on the positioning of a soil vent pipe (SVP). I’m converting my loft and adding a bathroom directly above the existing bathroom, so there is already an SVP in roughly the right location. I’m also adding a velux window on that elevation. As a result, the SVP ends up very close to the window. From what I understand, that shouldn’t be an issue in principle, but it does mean the vent needs to be at least 900 mm above the window opening. I’ve attached a sketch showing the existing arrangement in blue and the proposed arrangement in red. My concern is that this creates a fairly tall, exposed vertical section of pipe (around 2.5–3 m) near the pitched roof. I can lightly restrain it back to the chimney, but it still feels like an awkward solution.Does this approach work in practice and comply with regs, or is there a neater / more sensible way of dealing with this? Any advice appreciated, thanks!

As an update on this, I managed to get some details designed to push the rafters back and that gives me the option of getting 100mm insulation over the top. @Iceverge your suggested buildup - is this an issue from a condensation pov with having the less breathable material (PIR) above the rafters? This thread here seemed to generate quite a bit of debate and left me a bit confused on how to think about it. I would like to avoid having PIR between rafters given how tricky it is and the detail required. Also what about the VCL in this buildup?

I like this idea. In terms of building it would this raise the height of the roof above where it is currently? Already a bit over with counterbattons as it stands so don’t really have scope to push any further. Also given the rafters underneath will need to be 150mm I’ll likely need what looks like a “reverse” birdsmouth - is that structurally acceptable? Alternatively can I run the osb layer somewhere else maybe above where the existing rafters are maybe?

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?