Redbeard

Agree with @Iceverge. I am a great fan of floating floors (base/insulation/OSB/finished floor, with or without some membranes along the way) but perhaps the degree of 'out-of-level-ness' will have a bit of a bearing. May be hard to level it all out with sand and then not spoil the level as you lay? (Envisages a series of pulleys on ceiling each supporting a piece of insulation, jigsaw-style!)

Did/does BCO require a radon sump as well? The few jobs I have done which required a membrane also req'd a sump.

I take it they are clay tiles? It may be just my eyes but they look wider than 'standard' Rosemarys. I did a porch roof with 1920's clay Rosemarys which had been stripped off an replaced with concrete tiles, which probably won't look as good in 20 years as these looked after 90 (when I used them). Equally I have seen some clay tiles very badly spalled after far less time. My slate roof is 120+ years old, and one I was looking at earlier this week 150+. Both have had a lot of care and maintenance, and I would be pleasantly surprised if a clay-tiled roof lasted as long. But follow the others - close inspection and opinion on more than just the tiles, too.

"Why a cavity behind the plasterboard I'll put my money on air circulating behind the plasterboard." Service void, and yes, if the air barrier is poorly detailed you could be right, but with fingers crossed it could be tight as a drum.

Thanks for that. Well, provided the air-barrier has been well detailed at all joints, perimeters and penetrations you may hopefully have a good air-tightness envelope. Were all the windows and doors well taped in?

@GrantMcscott said: "We have plasterboarded and kitchen is in and some bathroomes but no carpets and some walls still need to be taped ect. When is the right time to do an air test?" I think I'd do it now. I would have suggested doing it before the kitchen was fitted and arguably before the plasterboards went on - when the main envelope was tight but before you'd added enough stuff to get in the way if you found leaks. You mention taping. Are you just joint-filling or full wet plastering on plasterboards? What is the house built of? If it's masonry do tell us it's not dot-and-dabbed plasterboard... please.

Danwood build said: 'DHW?' Domestic Hot Water

Not sure you can stop short of dubbing out. is the 20mm 'out' random or defined? Could you accommodate it with a 10mm toothed coat on the wall and (with possibly some tacky PVA to stop 'slippage') 10mm on the board? Use a nice soft lime mix.

Just taper the joint as @carrerahill says and the plasterer or joint-filler can tape and fill/plaster over it. I did dozens of jobs like this and it was never a problem. If you thought it might be then perhaps do the mitre, paint the 'raw' end with PVA and bed the joint between that and the flat ceiling in something like Sticks Like Sh*t.

Pro Dave wrote: "I fear we may have frightened @Tricky from replying? I do hope not." Yes, me too. Do 'come back' @Tricky. We want to help you get a comfortable home which is safe from the elements.

Think I'd drain everything down. Does the full reno include full re-piping? If so you don't even have to worry if you have not got lowest-point drain-cocks. Just cut the pipes.

@Tricky wrote: "Thanks for the comments. The 100mm celotex insulation was installed last week so no option to change now." Maybe not... Without an outside pic of the insulated shell I cannot be certain, but I guess you have a 37 x 38mm gap on the outside of each stud, and perhaps offcuts filling that gap. If you mark carefully the positions of the studs you could run another layer of PIR on the outside (unless the 6m and 15m dimensions are maxima under Mobile Home law - (later note, just seen a sugg'n that 6.7 x 20m is max so you'd be inside that). Then batten, then clad. I am sure you had checked this already (though I had to check it as I did not know for certain) T'internet says Mobile homes are not required to comply with the Building Regs, with the exception of certain groundwork and connections to mains drainage. Nevertheless it does not mean that insulation to, or in excess of, Bldg Regs standards isn't advisable from a current and future comfort point of view. Accepting that it is too late to do anything about increasing decrement delay you could still 'engineer' significantly more insulation.

What will the roof be? Structure, covering and insulation. Ditto the floor. Do those battens suggest that there may be only 50mm of PIR? I worry that you have a long time to be cold.

Maybe I am missing something, but it seems simpler to me than you feel it is. The WC is forward of that spigot, so there is room between the wall and the connection going into that spigot. Would my idea of elbowing within the wall depth not work? That way the 'Cold water feed for the toilet coming out the wall' won't be coming out of the wall until it's where you want it to be.

Cross-posted with @ProDave

Maybe I am being simplistic or misunderstanding, but if that is a stud wall can you simply not elbow up inside the wall and come out further up?

@AlshamalIf your roof ventilation is at the eaves consider getting your installer to staple some air-tight membrane (best) or scaffold netting tightly under the rafters at low level, so that they can then shove the insulation in to their heart's content without risking blocking the eaves ventilation. It also helps prevent 'wind-wash' or thermal by-pass - cold air getting in between the layers of insulation.

If you are on the wrong side to get to the 'slopey bit' of the latch then that suggests the door opens out towards you. Yes? If so why can you not get a thin wheel in an angle grinder and grind the latch off? Your 'explorations' seem to suggest that the latch mechanism is dead, so no net loss.

Green Building Store fully glazed external door U = 0.85. Cost incl VAT and delivery around £2000 supply only.

Agree with @SimonD. I would definitely go for adhesive *and* mech fixings. Make sure the adhesive is either full coverage or full perimeter bead and 'dobs'. I had a job done for a client and had had the full spec and method statement saying adhesive and mech fixings, only to find the fitters half-way up the wall, 'dry' (mech fixings only).

Sit it on pads, then, even if it is not post and beam. The copy is not great but have a look at http://www.ianwhite.info/THE_SEGAL_METHOD.pdf for the principle. If you are having stud frames rather than post-and-beam you can just span the pad footings with a horizontal 'foundation timber' situated above the splash-up zone. I have built a lot of Segal-style structures and am a rubbish photographer but I may be able to dig out some pics if that might help.

What's the build? Masonry or timber? If timber I'd do it post and beam and sit each post on a 'Walter Segal-style' pad, which could be anything from a paving slab to a paving slab with lois of concrete/crushed rubble below, depending on ground conditions.

What do you mean by a 'regular boiler'? You refer to a difference between a 'regular boiler' and a system boiler, so I think by 'regular' you must mean a combi (instant HW; no cylinder). As a lot of solar-water-heating exponents found in the past you can 'de-combify' a combi, effectively by telling it that the cylinder which you install at a later date is another radiator. As long as the sizing will be right I would, in your position, install another combi now (if I am right that it's a combi you have now) and use it as a system boiler if you want a HWC when you have refurbed.

As ProDave says pics would be good. I'd be looking at height of dpc above surrounding ground level, typical 'splash-up' height in the area (look for 'tide-marks' on neighbouring properties), 'softness' or 'hardness' of the surrounding ground. Have you been in long? Was it fine for years and now isn't? Have any other 'building circumstances' changed recently?

Do you think they leak air? If so do you perhaps have some claim against the manufacturer or installer, and if not, why do you think you need another set? I suspect a channel near the outer edge is more about shedding water tan being another place for draught-stripping. I have windows with a single draught-strip which do not appear to leak, and 3G units with 2 seals on te opening lights which seem tight as a drum.