Mr Punter

I have one in a student HMO. I have also had the undersink type with storage in an office suite. Neither property has gas. I don't think I would want one at home.

Strip the roof and re-lay. You need MINIMUM 50mm into the gutter. They are fibre cement slates fixed with nails and disk rivets. You could sort out the rest of the woeful bodges while you are at it.

I have done similar using resin anchors to face fix a timber ledger to the wall, then timber to timber joist hangers for the joists. It means you have more freedom in floor height and better airtightness. Your blocks should be fine for this as the ledger will have fixings every 400mm. Cleaning the drilled holes with brush and blower is key to a very strong fixing.

I would just go ahead and do a retrospective if it crops up.

Don't pay them until they get it right.

A more important factor will be the loss in floor area, which if it is 1.9% on a floor area of 160m2 would be about 3m2, which could be worth between £6,000 and £12,000 depending on location.

I have had quotes for this before and they were very expensive to cover the whole house, but can be handy for smaller areas. Get a flow rate / pressure check. You can request a very meaty supply from the water co. just for fire sprinkler purposes. Have it separate from your main supply.

Yes, mineral wool is far better than pir for this.

The res bars are good call. Easy to fit as well.

I have no experience of them but if they are a decent fabricator and you have seen their installations then why not?

Only if he gets caught naked.

Why do you think you need a demolition statement? Who is asking for it?

Well you will be by the time it is completed! Plan it carefully. Incorporate drainage along the back and through the wall. Design depends on height, what it is retaining and aesthetics.

Your builder and their contractors should provide you with RAMS (risk assessments and method statements) for all hazardous works (work at height, demolition, lifting operations, machinery operations, manual handling etc.)

If it is for asbestos, the builder can get this done. What did they quote for?