MortarThePoint

Under the stairs I think I'll struggle a little for height as 6 steps to the half landing this will be under. That means only 1200mm of space and the bottom of the manifold needs to be 600mm above FFL. Here's hoping the stair timber will be 200mm or less. I could mount (hori or vert) a couple of pieces of 4x2 to the wall and then put the manifold on that. This could allow a tiny bit more height, or if needed remove the top bit of 4x2 when installing the stairs and then screw the manifold to the stair timber.

I'll just be screwing my manifolds to the walls. In two places this will be blockwork walls so I anticipate using masonry screws like the ones below with some appropriate steel washers. When mounting on a studwork wall, should I use some form of vibration isolation as I could imagine the plasterboard acting as a sounding board. Screwed to the studs, but still. https://www.screwfix.com/p/easydrive-pan-concrete-screws-6-x-60mm-100-pack/9665r https://www.toolstation.com/masonry-torx-frame-fixing-screw/p16209

Purenit (link) looks like good stuff. It's a bit late for me as I'm not sure I'd have space for anything over about 10mm thick sat as a bridge over the cavity and then masticed under the sill. Mocked up below. The Purenit would probably need to be bedded on something which would add an additional ~5mm. I don't know whether 10mm of Purenit would be stiff enough. I think the back of my door sill will be approximately 30mm behind the cavity edge and so the sill would cantilever 30mm and so the screed cantilever 70mm (100mm cavity). I'm looking at having a 50mm screed now, so maybe adding a small strip of mesh would be good. If there is a product like bed joint reinforcement that adds strength in two dimensions, not just one, that would be good to embed in the top of the screed to help with tensile strength.

Thanks, looks like a good arrangement. Is that a timber frame above ground level? Looks like very thick walls.

I asked and never got an answer about this from the Thermabeam guys Seems like everyone does some form of bodge where they rely on the screed to cantilever over the cavity a bit. LABC drawings call for a structural cavity closer or a reinforced cavity closer, but talking to cavity closer manufacturers there doesn't appear to be such a thing. This drawing shows a way of doing it, but still relies on the flexural strength of the screed as the cavity closer isn't structural: https://www.slideandfold.co.uk/alumina-low-threshold-with-cill.pdf Good luck drilling the 'External Brick Work' that close to its edge.

My Cavity closer should do that for me as the door frame won't extend further back than the cavity closer (will it)

Was that effectively covering the area I have shaded red there?

This doesn't make things much clearer, but I think it's saying there should be DPC under the door to stop rising damp https://www.labcwarranty.co.uk/blog/spot-the-defect-damp-proof-membrane/

I'm not sure what I should be doing at the door thresholds in regards the Cavity Tray. Below is a photo. You can see the floor membrane which goes on to bridge the cavity and all the way to the outer face of brickwork. There is a cavity tray above the membrane and you can just see some of it jutting out of the blockwork (circled RED). The cavity tray has been cut to lie flat on the membrane in the door threshold. A 40-50mm thick screed is going on top of the membrane and the timber you can see is there as stuttering, with subsequent perimeter strip to be added. What should I do with the DPC? Should I tuck it out of the way so that I can then lay it onto the screed, or should I cast it under the screed? The plan will be to later use slate or something to cross the cavity under the door frame and then fill any gaps with Self Levelling Compound. Does this sound sensible, or is there a better option. The thresholds are not level, with a step up from the patio of around 125mm. That is except for the front door which is level, but under a porch so should be dry. As it's not a level threshold and will be under the sill I don't think this DPC really matters does it?

Looks good and very neat PIR insulation

Easy when you know how! I'll have to avoid crossing over like you have as I don't have the mesh, but where I have serpentine pattern I can just go between two loops. I see you have put your sensor at the hottest point (B from my original post)

Cool, that allows fixing them if they break which is good. Can you recommend a type of pipe to use?

I've been getting my bits from WUNDA and wondered ( ? ) if their floor probes (aka Thermostat sensor) are any good? Being something that gets cast into the screed I can't change my mind later. Also, in terms of placement within the room. Should they be placed near the start of a floors circuit (B) or mid circuit (A)? Near the start makes sense to me as the purpose of the sensor is to protect floor finishes and so the hottest point needs to be detected, but I may be missing something. Finally, I also assume that the Thermostats can only take one temperature sensor input. @Nickfromwales Is the doctor in session?

This is cool, literally. If just looking to cool the floor, is it just a matter of having the right ASHP? Sending 15C water through the UFH pipes feels pretty low risk from a condensation perspective. If concerned by condensation on the manifold, one can always run a separate dehumidifier nearby or perhaps just a fan blowing over their surface.

What flow temperature do people use to cool their UFH? I'd imagine wanting to use a higher temperature (to avoid condensation) than an air blower would need.

Those are around 1.4 kPa of screed weight.

I agree and the leakage is what will allow it to 'breath' and push air in and out of the living area. Yes, it's nothing. I'd prefer that to the air going in and out.

But unless there is a sealant, it's going to leak out. If not, it would raise the floor by approximately (1/20) * 25ml / 7cm * 7cm = 1/40 mm which is admittedly tiny, but probably enough to open up an air leak to release the pressure.

I hate working this sort of thing out as sometimes ignorance is bliss. For a gas, pressure (P) is proportional to temperature (T) in Kelvin for a closed volume. Therefore if there is a dT there is a resulting dP. With the UFH off for some time the floor will be at the same temperature as the room. With it on, the temperature will rise above the room temperature by dT (e.g. rising to 36C giving dT=15C=15K). That's going to create a pressure difference of dP = (15/300) * 1Atm = 1/20 Atm = 5kPa in any air trapped below the floor. The weight of 50mm thick screed is around 2.4kg/m3 * 0.05m * 10N/kg = 1.2kPa. Presuming a continuous air gap under the screed that would lift the screed if it didn't leak out, so it will leak out. That's tiny you'll think, but most castellated panels increase the volume of air involved greatly. The volume of the castellation and ridge per unit cell is probably around 25ml (a shot glass) per 70mm x 70mm unit cell, so 5.1l per m2. So, a 20m2 floor will breath 5.1l per cycle. So what? I don't know, but I thought it was interesting. I had planned to glue down my castellated panels, but this makes me think of the air going in and out pushing out any warmed up fumes from the glue. Probably no biggy as the temperatures aren't very high. Has anyone thought about this before? @Nickfromwales you normally like talking sense against this sort of nonsense.

My manifolds are all going to be in cupboards, so is there any point in putting them in manifold cabinets? I can see them being useful if in a rental property (locked) or having the manifold in a room not inside a cupboard. The only reason I can think I could justify using one is to save the manifold getting knocked by someone tossing Henry (or Harry) into the under stairs cupboard. I don't think it would stop spiders of dust. Does it look unprofessional not to have one? What did others do?

So just to be clear glue only, no screws or bolts?

Poor guy, but hopefully he saw the funny side eventually.

I just found this link too: https://www.sunamoon.com/articles/fix-down-toilet-without-screws.htm CT1 looks good. I had a friend you sat on the toilet and it sank through the floor. When he subsequently flushed it went everywhere. All round at a new girlfriend's house. Didn't put her off though as they are now married.

Can a glued down toilet weather the storm?

Unless you're Jim in American Pie