Nickfromwales

Hi, and welcome. A word of advice.... IF you do find a plot, tell NO-ONE until you own it! London is so densely populated, apparently the rats are saying amongst themselves "You know, you're never more than 5m from a human being"

Just make sure you zip tie the ducts tight to the lower chord so the cellulose goes over the top of them, bringing them into the insulated envelope.

Whack the ducts in, install a good quality airtightness membrane, hold the membrane in place with service battens at 300mm o/c's, and pump the bugger full of cellulose.

Happy days. The external was an "if" so don't panic about that. All looks good, but lets delete the assumptions All voids in the actual upstand need to be packed solid with rigid PIR. Foamed and foil taped to leave zero gaps. The joist depths are to be filled with rockwool / other?

Yup. Something like Marmox on the outside would help, but not essential. If you can get a 10mm board outside then do that too. The only thing I'd add is some continuation over the upper timber of the upstand, as you don't want any (ideally) of that meeting room temp. The issue is exaggerated here because heat will rise, plus moisture, and they'll both be trapped here and fighting it out against anything 'cold'. More Marmox with a chamfered tuck into the angled section would be beneficial.

Relax, we promise to not let you feck this up The worst cold bridging would be between the timbers at the top, and the plasterboard. Easy solution; use Marmox at 25mm thickness instead of the plasterboard and plaster it directly. Stuff everything with rockwool immediately surrounding the upstand, and Bobs ya Uncle. Not a single mention of Fanny, that would be rude!

Yup. You catch on quick, Sherlock.

Yes, the rotating waste is (was) a revelation. Have you looked at Diamond wetrooms? They have a clever tray which you pick up and rotate 180o and the trap moves 'sides' of the joists.

A decent tiler can make just about anything work.

You can do the same with regular tiles, just the cuts have to be a bit more inventive. Also, depends on whether you've gone for linear trays? Not too late to change and mosaic? Or is your preference for large-format tiles only?

All the area around the actual shower former (Wedi) is slightly elevated compared to the perimeter of the former highest point, eg so I could bench the mosaics in and have a fall all the way from the towel rad to the drain.

Eh? You cannot tell where the former ends if it's being tiled over?

I'd say that's possibly the slates cooling down each evening. Probably be worse while we have some sunshine, and almost disappear during winter. May settle, as new houses do tend to do these things.

Flow will be flow, regardless of duty, so the energy in the pipe gets preserved and delivered where it needs to go to.

You just bench the missing 100mm in with tile adhesive and an off-cut of cement board / other.

One pipe leaving will be flow at the manifold temp, and the return loop will obvs be at the lower temp. Deciding which pipe runs where offers some minimal but additional manipulation of this distribution. In a PH or thereabouts it does become almost moot as the slab will almost completely uniformly acclimatise and there will be very little difference between the two. I only insulate the pipes going to the far side of the dwelling from the manifold, mostly to keep whatever is in the pipe, in the pipe, until I want it 'out'.

You can't cut a 1300mm tray down to 1400mm?

Why aren't you putting formers down and tiling over?

I have no idea, just the only thing I ever hear that's reported as doing what you are hearing / experiencing has been the roof. Mainly SIP's roof and with metal standing seam. That's the only bit of the house that heats up and cools down (expands & contracts) quickly enough to generate noise. Do you have tiles / slates / metals?

Not in any of my experiences. BCO walked the job, warranty folk wandered around behind him taking notes.

Would be a good guess, seeing as it took so little to provoke this into leaking.

That's what I did on a build in Gravenhill. MBC TF so only a 35mm service cavity to lose the tails within, and SWA just would have been impossible to get where I needed it to go. Flat bar from B&Q iirc, and shows up well with a stud / metal finder.

If it's daily, then it's probably more closely attributed to heat / cool of the roof structure. I very much doubt your masonry walls are on the move!

Surface contact (cross sectional area of the pipe > surrounding concrete) determines how effectively the transfer of energy is, and if you want to effect cooling this becomes a valid point of consideration. Heating is barely worth talking about and almost manages itself; just look at examples of folk on here at all ends of the spectrum, some at 100mm o/c and other at 400mm o/c, some with a buffer / some without, and so on. Nobody has yet yelled for help as their system is 'out of control' for heating. Closer o/c means the slab will be more reactive and pipe is cheap as chips, but I also cannot experiment in my clients homes! Belt & braces (for the cost difference vs risk) will always be my choice. Cooling is the 'enemy' as the input flow temps need to avoid condensation risks, ergo you can only effect a certain amount of 'change' over x period of time, and the less CSA and volume, the worse (more elongated) that becomes. Further to this, the dwelling type has further effects which need to be factored in, and then you also need to understand if auxiliary cooling via AHU's can bolster the effect and manage the times between the slab coming into useful play. Cooling likely needs injecting at the small hours, so as to have some kind of momentum for the sunny morning to midday, and the kick in the knackers there is only some of it can be dealt with from PV then. One client uses the cooling 'long & low' (so nigh-on constant flow of "cold-ish" water through the UFH)but I also specified an intelligent AHU which speeds up the MVHR fan speeds when it detects cold water input into the heat exchanger, eg to increase the volume of cooled air (heat energy) conveyed, and I'm still gathering feedback / data as to how that works out in an occupied dwelling but controls seem to be the bug bear with this type of flip/flop setting. Trying to get something simple and recognisable to hand over to Joe Public is a challenge! I am very impressed with the Steibel Eltron ASHP we installed recently, but more so with the controls. DHW goes direct off the ASHP and cooling / heating of the UFH goes through a digital blending set (fed from buffer when either warm or cold) which then goes direct to AHU. The advantage here is that I can send 7oC water to the AHU to max out its cooling capabilities vs minimising air flow speed rates, and the blended sum goes to the UFH so I can decide that to be 16oC, simultaneously. I think a few of the more boffin-like members on here have come up with the same solution, but this one is out of the box and more 'fit for human consumption'. I just wish there were more hours in the day so I could read everything written on here about the subject! In the meantime, I may just go on to recommend and employ the (very expensive) Steibel setup, as it actually works out as being value for money when you look at it as a holistic and comprehensive turnkey heating and cooling arrangement.