Redbeard

OK, fair point. I should have said 'my personal preference is for AT tape' and then backed it up with anecdotal 'evidence' (over quite a lot of years) of some quite good, quite strong and very sticky foil tape and some very weak, not-very-sticky, frankly very awful foil tape which was particularly weak in tension and would split when returned round 90 degree returns. A few bad experiences led to a 'once bitten, twice shy' attitude which I retain for my own work. I'm just off to comb my torso now...

I think the IC analysis 'thought it was OK' as it ignored the 'interstitial plasterboard' and assumed (as all IC analyses do AFAIK) that the VCL in the insulated plasterboard was perfect and taped at all joints and perimeters. The nature of insulated plasterboard makes this impossible. I have a strong suspicion that the musty smell is the paper on the 'trapped' plasterboard 'festering'. There will almost certainly be other issues to sort too, but I think you need to remove the insulated plasterboard, remove the original plasterboard and VCL, apply PIR (if that's 'to your taste') 'in the raw' (not as a plasterboard laminate), tape all joints and perimeters with air-tightness tape (not cheap fragile foil tape) and then batten, fixing through the battens to the TF wall to hold in the PIR. If you are a pessimist (which with water vapour I think you should be) pre-fill the holes, gun in silicone, and wind the screw through a 'silicone grommet'. Nothing is perfect but that is going to be the best chance you have of a somewhere-near-perfect-ish VCL. I am sorry this will not be what you wanted to hear.

Although some have done it I am not happy with the idea of trapping gypsum plasterboard in a sandwich between insulation and insulation. So to clarify, the timber wall is the original, yes? If so I think you should have taken the plasterboard off before adding the IWI board, and only have done that if an IC analysis said it was OK (although I think you did do that IC analysis and it suggested you'd be OK if I have read that right. Obviously the IC analysis software and I don't agree re a plasterboard sandwich!). @Nickfromwales has posted while I have been typing, so off to see what he advises.

PIR is a mixed blessing as many will tell you. V hard to get a perfect fit and as humidity changes a 'perfect fit' may not be one any more. I like flexible wood-fibre, but it is not cheap and will need just short of twice as much as PIR for the same U value. The main thing with UFI is that as you warm up the room you cool down the floor structure, increasing the risk of condensation. Excellent cross-ventilation (no 'blind' areas) can help a lot. Beware that UFI does not always appear to obey the laws of Building Physics!

I have no idea about the cost, I am afraid - it depends on your local 'market' - but I would engage a structural engineer first to prepare a specification. I cannot see clearly what goes on under the stairs. Is that a door or pair of doors to an 'undercroft'? I assume that 'rusted beam' is over a door or doors. Is the space inside the doors a WC, perhaps, or just a store? Is it necessary? Could the structural support be made simpler by infilling the 'void'/store? But then what about the risk of transferring damp to the ground floor room adjacent?

Yes, it will be slow, but it will begin as soon as you have moved the 'pre-conditions' as described above. I'd leave it to do its thing and use the de-humidifier you referred to.

Ah! Thank you. I could not see its base-plate.

If the world is really quiet I can hear my 3 CV2s. If it isn't (and it usually isn't) I can't hear them. Even when I can it is not bothersome.

What is the pipe? How will it be protected and how will it interfere (if at all) with the integrity of your foundation?

No, don't even consider DPC injection!!! Everything worked well (as far as you have said) before the builder put a hard surface above your DPC. All that needs to be done is to remedy that locally. As @ProDave said, probably take another half-block away so that you have a 'trench' of 200-225mm wide. *However, what is retaining the edge of the driveway? Assuming it is a standard block paving job and bedded in sand then probably, 'as-built', the house wall will have been the 'retainer' which stops the sand running out from under the blocks, and the blocks 'drooping'. If this was the case, then removing half a block as the builder has done, and another half as we have suggested, could (if no other method has been provided) lose you your 'edge restraint' and gradually the sand could wash away and your blocks drop 'into the ditch'.* The Building Regs require a minimum 150mm (6 inches) between external ground level and the DPC. That is based on an assumption that rain will 'bounce' 150mm max. No-one has told the rain where I live that it is only allowed to 'bounce' 150mm, so it goes for 300 instead! At very least you should revert to the former (we hope) position, of a minimum 150mm down from the DPC to any surface. Ideally you need a soft surface (the gravel will do), and it needs to be far enough away from the wall that rain won't bounce onto the wall above the DPC. In certain wind conditions, your 4 inch (100mm) gap won't be enough to stop rain hitting a block and yet still being able to wet the wall.

Just for clarification, 'my' parge coats are approx 6mm trowelled lime plaster. I know others here use a brushed-on weak(?) sand/cement mix, but mine is not that. Where old lime plaster in good condition with good adhesion still exists, and there is no impermeable coating, I leave that (probably c 18mm) and simply augment where it never was.

I've done lime parge coat on GF and FF walls and in the ceiling/floor space, tight around the joist ends. Leave plaster to dry thoroughly, prime plaster and joist with air-tightness tape primer, then tape. Usual tricky spots are at joists parallel with flank or external walls, where you cannot get in to plaster, prime and tape. Probably one of the 'gunges' or FM330 in those spots.

Yep, looks pretty straightforward. Good luck!

Agree with @Conor's concerns. If I understand that 'spaghetti' right then the 'resting' water level in the trap will be above at least the smaller of the flexi-wastes, if not both. No wonder the dishwasher isn't draining properly (again, if my 'reading' is correct).

Hi. Suspended GFs do not always appear to obey the rules of building physics! Having tried on a few occasions to use passive stacks to ventilate sub-floors I think I'd be tempted to add a fan somewhere in your plan (and a sump/drain in case of lots of WV in the 'stack' running back as condensation.

I don't know how renowned the MCS HL calc is for accuracy, but if it is 'within tolerance' and the contractors are quoting to provide 21 degrees to Zone 1 (living room(s) and 18 deg to all other spaces at whatever the low-end assumption is for external temp *without FF bedroom heating* then you are probably OK, and have 'provided (for) heating to those rooms'.

@JamesPa makes a good point. @Rudski, you say: Have you had a full-house heat-loss calc done? If that shows that the proposed provision (with no rads to bedrooms) *will* achieve the 18/21 desired temps in all rooms then I think you have met the requirement which @JamesPa refers to, as long as the quality of workmanship means that the actual meets the plan. If you are relying on a 'gut feeling' then I guess MCS/the installer do not have to have the same gut feeling as you.

''Posted 15 minutes ago (edited) ''@LaChab, Google translate suggests that Rahmenaussenmass means 'external frame dimensions', suggesting (to me...) that that 85mm section is inside. But perhaps I am misunderstanding. Edited 14 minutes ago by Redbeard'' No, I got that completely ar*e-about-face!! @LaChab I think you must be right and I am wrong. So they are inward-opening?

@LaChab, Google translate suggests that Rahmenaussenmass means 'external frame dimensions', suggesting (to me...) that that 85mm section is inside. But perhaps I am misunderstanding.

Ah... Are they inward-opening? I had assumed they were outward-opening, but I cannot find confirmation of that.

Just searched for what KF520s are! Looks enough space there for what I have described but I may be wrong, or you may just like to see a lot more frame than I'm happy with.

I guess it depends how much of the stile you can 'lose'. Usually you can 'lose' up to 20mm without the end result looking stupid. If I had the set-up you have I'd maybe use 2 x 9.5mm plasterboard and once 3mm skim was on you'd have more room for tape.

Most window-taping I have done has been onto the inner face of the window (by less than the depth of the plaster or plasterboard) and thence onto the masonry. It was done after the windows were fitted.

I have seen very poor taping done by contractors and very good taping done by householders. There will also be lots of crossover, of course. Not sure why the Profil would necessarily show on the inside. What shows (or doesn't) depends on the depth of the reveal finish. Pro Clima Profil is designed with a split backing-tape specifically for windows. Equally there is no reason for the split tape if you are good at applying tape, so you can use Tescon Vana or similar from the same manuf'r.

Yes, if there's enough frame left at the top. Look for 'uPVC window repairs' locally and you'll probably find someone who will do it.