Mr Punter

That is interesting as the OP did not take in the lodgers until 6 months after moving in. Any idea how long they would have needed to wait before letting to avoid liability?

The shower bath types often have a fixed screen, so no leaky gasket flap thing.

Option 1. Dig a trench down to firm ground about 300mm wide. Compact the base. Layer in some type 1 and compact, then concrete under and haunched to paver as you have shown.

It would be helpful if the plans you have posted were all oriented the same way. Don't plan the bathroom just for your young children. You may soon be at a stage when several people want to use the loo, brush teeth, have a shower etc. at similar times. Morning rush hour before school / work can get congested. We once had a double sink and that worked well for face wash and teeth brush for 2 at once. You may find that a small ensuite or at least a separate loo would be handy. A shower bath can combine 2 functions and save space.

No if your loft conversion was signed off it has regs. If you do other works they will be a separate sign off.

The timber will probably be 195 x 45. I think it is good to centre the steel plate top-to-bottom so it doesn't bear directly on the timber above / below. I think this may be a struggle to source.

Yes I saw those and they look v good value compared to the commercial stuff from plasson etc but we are in a tight space and the plumber suggested Ts from a 28mm. I know not much about plumbing but thought if the purpose designed one leaks you would need to replace the whole thing where with normal fittings maybe not.

I imagine it is fine but we are feeding 8 flats. We have a new 32mm MDPE supply so we are thinking 28mm copper with 28mm x 28mm x 15mm reducing tees to each of the meters. The 28mm will also have a cold water accumulator. Current setup is 15mm spaghetti, so electric showers tend not be too impressive.

I think you will need to change the study window to and escape window

I use a dehumidifier to dry washing in a small utility with no window. Normally I don't have the extractor on. The cable through the wall plugged into a socket the other side is fine, especially if you don't need the dehumidifier elsewhere.

Cutting the openings looks like it was quite a task. Neatly executed. Were they on a price?

I have asked a plumber to make up a manifold for cold mains water and he is suggesting 28mm copper. I will post a picture if he gets it done.

For the floor you can cover it with DPM, then Celotex, thin polythene and top it with T & G chipboard.

Is it the case that the planners will not let you demolish this? It is certainly not pretty. It does have a pyramid vibe though so you could decorate with hieroglyphics.

The studs need to be in a line or they need packing.

You can use either but I would go 22mm. Egger Protect is good.

It sounds like you are renting the flat which would mean asking your landlord to sort this out. He should have ensured that the adjacent owners had the ceiling replaced with one of at least the same fire and acoustic performance.

It is hard to say for certain but it looks like the steel supports are structural. Was this 2 openings? The outside post looks fairly corroded. I think a structural engineer would be best placed to advise.

I don't think there is much in the cost.

If there is a TPO and it is not on your land I don't think that it can be easily removed. If this is just for a garage, do a few cracks matter?

Running copper through joists is tricky. Most builds use chipboard upper floor decking which is fitted before first fix plumb and electrics. If you have a long run of copper pipe perpendicular to joists you will have issues.

Yes. Do you have any photos of just before the window was installed?

I understood that you need Part P if you are adding extra circuits and that moving switches etc in existing circuits is OK.

We did a basement in ICF a few years ago and had a blowout. Luckily we could wedge some timber between the wall and the face of the excavation and the bulge was not visible as we did a metal stud wall inside. Still, I don't like the thought that during the pour there is so much risk.

Normally you would have a cavity tray and weepholes above the lintel to sort out the top then a cavity closer at the sides and the bottom. The main weather seal is between the frame and the outer leaf and is normally mastic or Compriband. Any water getting past this should get stopped by the cavity closer and directed into the cavity.