Nickfromwales

With a cyl stat mounted low on the UVC and the ashp heating it on demand you really should never struggle for DHW. Both tanks will have to be depleted before immersions are considered, so if you went for 300L a piece on the cylinders you should be fine. @joe90, the sizing would be different for you as you don't have / intend to ever have pv?

Plumbing the ashp direct to the UFH is not the issue here. You can, and without issue, BUT you then have to consider the peripherals. If using the HP for DHW you'll possibly be into defrost cycles for a part of the year if not more, dependant upon your consumption / usage patterns etc. With a buffer you have a stored body of water that the HP can suck back for defrost 'assist' therefore leaving the UFH loop volume unaffected. Also, as @TerryE and @JSHarris have recently discussed in cross talk, the ashp may not be comfortable modulating that low plus it will then be very likely to short cycle. @DeeJunFan if you want a design then refer to my first which is ashp to both cylinders accordingly ( 38oC to buffer TS and 55oC to UVC respectively ). Pv divert to DHW only and 2 x 3 kw immersions in each cylinder so you can run both space heating and DHW in the event of ashp failure in some reasonable capacity. Sizing of cylinders is down to space and intended consumption, which is largely to do with DHW, so perhaps elaborate on that a bit more first .

For the grief with the stove installation, unless you intend to use it a lot, I'm with him. I completely disagree with him about driving the preheat into the DHW tank as that's nonsense. If your Pv is generating at all, then your likely UVC ( proposed TS ) temp will reside ABOVE the low grade temp range of the ashp 'pre-heat' ( aka high CoP ) yield, so basically you'll be COOLING the cylinder with the ashp and that's obviously not the way forward. The only way to link the ashp to the DHW tank is to accept the hit on the CoP and drive it at 55oC. Essentially with your new guys proposal you'd never get the ashp to supply any heat to the TS unless it was switched on from cold. As it would prob never get that cold it'll never ask for low grade heat input. Regards to the recommendation for the TS instead of the UVC then it's a bit too difficult to just say it's a good / bad idea. The primary tank for low grade ( in previous chat ) would sit at a temp low enough to not give masses of unwanted latent heat loss, but will then allow you to reduce the size of the UVC. The UVC will be the tank with the higher, possibly nuisance, latent heat loss so that's the one to focus on. If you change to a multi input single TS, it'll be very high temp ( 70+oC ) and it'll need to be a biggy. More losses, less efficient, more ( *) connective pipework to leak heat away, and zero opportunity to preheat ANY DHW from the ashp, ( * ask @Declan52 about the importance of keeping the pipework related losses under control for real life feedback ), plus you'll need to keep boosting it with electricity to max out the correct temp, as, even at 55oC, the ashp is not at all suited to directly and singularly running a TS. ( IMO ). Pointless in going to the efforts you have done with insulation / airtightness etc and then have a horribly inefficient heating and DHW system. Sorry for the headaches

Sealer will work, but you'll have to keep re-applying it in a high frequency area such as a shower. Prob once every 6 months at an estimate. It takes minutes to do a shower area so no real grief TBH. Regular light cleaning will pay dividends.

Clear CT1 is excellent stuff. I did a couple of bathrooms with Mermaid panels and used my router to do all the cuts, scribing perfectly to the shower trays etc. The base trims they sent were utter crap and a PoF for sure, so I binned them and devised my own solution. Basically a half inch bead of clear CT1 with absolutely no voids at the foot of each panel and then the panel dropped into / onto the bead. The panel then displaced whatever it didn't need and the excess was tooled off and cleaned away with a combination of masking and cleaning ( with wet wipes first and CT1 MultiSolve spray ) afterwards. The result is a clean sharp edge and a neat, near invisible watertight seal which is also an adhesive bond. CT1 also doesn't suffer and degrade like most silicones do, but you do then also retain the option of retrospectively siliconing over the CT1 to give a purely cosmetic seal, ( with a colour matched silicone for eg ) which can quickly and easily be removed and redone every few years if so required. Fwiw, regular non abrasive cleaning will massively decrease the intervals between the silicone needing replacing / redoing.

Fwiw, a cheap decorator will make it worse. Use a good decorator and they'll work miracles. My decorator did a ceiling for me instead of us skimming it and I remained sceptical. The following day I genuinely looked for the seams and couldn't find them without really searching for them. Customer was over the moon. Cheap enough to do and looked great. As always...... "It's all preparation, Pet" .

Smooth with filler and then lining paper? Nothing on a roller will do anything to flatten and level walls, they'll just be a way of bulk loading the wall with a filler compound 'paint' which will then need sanding or rubbing back to achieve an even finish.

Everything plaster / render / brick / stone I meant . A lot of people will do all the heavy work and clean up and then mop all the floors / floorboards with a weak pva solution to 'size' all the surfaces and lock the dust down.

Have you included a buffer or TS to compliment the boiler setup? Quite essential if the heat requirement is low as the boiler may never end up condensing ( if feeding th Ufh directly ).

A great site with a poor owner. Ah well, at least he's getting his beers paid for by keeping a dead body alive.

Pva for everything . Just different dilutions, through to neat, to suit each situation. If you want to go mental you can use "blue grit" and that'll stick anything with everything. Link

Woodchip wallpaper is your friend

Oh, and welcome to the forum. . Feel free to start as many varying threads as you wish The info gathered here is priceless, and we'll never grumble about hearing and documenting what went wrong, how to put it right, and from 'new-to-building's favourite...., how not to do those things in the first place . That's my favourite excerpt Chin up, and crack on. ?

Just ask either @PeterW or @recoveringacademic ( Ian ), our Admins, and they'll update your blog privilege .

After all your hard work, and the fact it's timber frame, I'd deffo go for a skim coat as it'll be the icing on the cake. Nowt worse than seeing everything under the paint 'coming through'. .

I got a bit lost here . If your going to PB the walls and PB the reveals around the window, but you want to tape and fill / join ( what I would call dry line ) then you can buy this reinforced paper tape corner. Just cut to length and it 'snaps' to form a perfect edge which you then blend out with a quality bulk filler such as Gyproc Easi-fill. Hows that sound?

Last extension I did was TF and PB with a full skim coat throughout. Absolutely showroom finish with lots of praise from the customer. Even more praise and thanks from my decorator who had to make the existing house blend in, ( which was all 'taped & jointed' aka dry-lined filled and sanded ) where you could see EVERY board junction, EVERY door frame head, and was just dire in comparison. Difference with me is I'm mega OCD on the finish, as if the paint ain't looking a million dollars wtf was all the effort up until then for ?

The amount of time and effort that will go into that, for what I believe will be a far inferior finish vs PB, just isn't practical imo. The ply will have indentations where you've screwed it on the curve and PB just covers so well it's a no brainer for me. I think you'll put a lot of effort in and kick yourself afterwards with painting ply TBH. Plus if you've got a PB surface adjacent it'll stick out like a sore thumb. PB will give the clean sharp look your going for, ply won't. You might get away with bendy MDF but I wouldn't even quote to do that for someone as it'll be a can of worms that looks good one day and all cracks and opens up with time.

I've never heard of anyone anywhere filling and painting ply / osb TBH, regardless of location. How will you form the external corners of each window 'bay'? If you have PB on the face walls then how would you transition between the differing materials ? Skim / taping & filling is done countrywide, that's a discipline of its own right, and commonplace, so I fully understand that it can be done, just not over bare timber afaik. At the VERY least I would get some 6 or 9.5mm PB and get the ply covered, but in your instance I'd just pack out and PB first as last TBH.

You can't plaster directly on to timber .

So you can plaster?

Everyone's favourite kind ?

Browning is pretty good for bulking out actually, so I'd second that. Get the second coat on when the first goes hard, but not when the first is dry otherwise you'll have to PVA between coats.

Sorry, yes. No need to guess if things will line up that way, and you can then squeeze max fall out over the distance .

Plus one to just doubling up the layers. I did a 2 layered garage roof as the customer wanted to be able to walk on it when coming out of a upstairs French door. With 2 layers you could park a car on it.