Mr Punter

I have not made a section 75 claim but will be interested to see how you get on. It does seem to favour the consumer. Please let us know how it progresses and what you had to do.

The foil tape on the joins will not last long, especially if the boards have any dust from cutting etc. Thin polythene will work fine. 150 is tricky to cut but if it is one big area may be OK. I would buy foil faced. Unfaced will turn to crumb / powder when walked on.

Those plastic sills are never brilliant as thermal breaks but I suspect the issue may be that the floor adjacent to the doors is not sufficiently thermally isolated from the wall. Do you have a thermal image of this area? Also, do you know what insulation is under the floor? Door thresholds are often a real thermal weak point.

Normally you would have the meter and stopcock near to where it enters the property but I don't know the layout for yours. UU are keen that the pipe does not freeze, hence the 750mm depth.

Is it the tiles or the plastic cill that are not right? If it is the tiles, @MikeGrahamT21's overcill looks good. You could put some packers along the back to give it some fall.

Where we are the water company want to inspect the open trench or we record the depth with a tape measure and photos. On your job they should be able to get the 32mm pipe to work without much trouble. I see that UU will accept a video of the pipework using their app and they have a proposed arrangement for shallow entry pipework. Depending on the layout, you may have to abandon the existing pipe and start again. Can you have the meter near to an outside wall?

The draughts are to do with airtightness, not insulation. Externally you need to run sealant between the frame and the brickwork and under the cill. Get a nice tooled finish on the sealant. Add extra sealant between the cill and the base of the frame. If the floor adjacent to the doors is cold it may be because of air leakage, insufficient insulation or no thermal break, such as a perimeter upstand of PIR.

What is going on the floor?

Yes triple glazing is about 31kg /m2, so the 4m2 window would be about 124kg. Even if the glass was 6mm in all 3 panes they would weigh about 186kg. It is easier to ignore the frame and just use the overall window size. I think the 350 - 450kg was maybe for a different size but again did not inspire confidence that the OP should be doing this.

The project is a new build block of flats and the OP does not seem sufficiently skilled and competent to be responsible for window installation.

Th comment was for the OP, not you!

Hawthorn is high water demand. Maple is medium. If the hawthorn is existing, they will calculate on the fully grown height, so best clear completely ASAP.

If you have to ask the question here, you are not competent to undertake this work.

Hello @frslam. This seems to cover most of the ground already explored in your thread earlier this week. A small gap between slates is good as it reduces capillary action letting in water. I understand that you considered that your roofer has not done the roof to your satisfaction and you have parted company, finishing the roof yourself or by others and you are now looking at who may owe money to whom? I am not sure how this new topic will progress things.

Agreed. I would want the horizontal centre of the TV to be in line with the mantelpiece. To the right. You could easily conceal all the cables and kit in the alcove.