Mr Punter

This is one I had fitted in a project about 17 years ago.

If you only need to wait a year for the charge to be wiped out, what is the issue? Is any money owing under the charge?

If it is airtightness you are concerned with, some mastic or tape would help. I don't see the point in insulation there as it is too small a gap. When I have had bigger gaps under sole plates they are normally chocked up, then we will fill with mortar from a pointing gun.

Roof trusses may be better. Lightweight and made to measure. https://www.tailormadedesigns.co.uk/products/standard-truss?variant=46720881426712

All of it. It is to do with fire risk and high rise buildings, not what level of insulation you have fitted or how much water the building uses.

Yes 32mm treads. No MDF. They are well made.

RICS don't share your view. https://www.rics.org/news-insights/building-safety-act-faqs

These were communal stairs for flats, so 250mm going per tread and lower pitch. We also used chunkier materials to hopefully mitigate noise.

The Building Safety Act focuses on building structural safety and fire safety only, Nothing to do with your u values. It is aimed to prevent future Grenfell tragedies, so high rise buildings and fire safety. It will not apply to any of the works discussed on this forum.

If you add your stair to the basket in stairbox it will show the weight. I had 2 flights, 1 was 150kg, the other was 200kg. They were commercial spec.

I am very impressed that you managed to cut a new drip groove.

Warm roof is best but the Velux windows are too close to the deck. Could you lose any ceiling height?

It did not strike me as being a sales pitch, just an academic research questionnaire.

It may be different in Scotland but we in England we only do sound testing for compartment walls and floors - between flats and dwellings.

Of course they claim it is normal because they are unwilling to accept responsibility and they would rather lie. It looks wrong to me. Where did they source the glass? Find out who manufactured it. Get it replaced.

As long as they are separate there is no issue. Moisture will not jump from one to the other.

7.3N Aircrete blocks will be fine. Don't shotfire the soleplate into them.

Can you allow for 225mm above the slab to get to your new level? That would give 150mm insulation, 55mm flow screed and 20mm floor finish.

They don't need to be the same level. Also you can have more than 1 DPC if needed.

Yes. They use a different form. https://www.gov.uk/government/publications/registered-titles-part-transfer-tp1

Are you thinking to drop the render down by 300mm as well? Draw it on the elevations and see what you prefer.

If you use the quote function instead of the Greater Than symbol, @DevilDamo will get a notification. Anyway, I think it is just how much you increase the floor space.

You will need your mortgage provider to agree your scheme. You can then go on to build the new house, sell your existing house as a new title, retaining the land on which the new house is built.

I know you have already started work, but did you explore demolish and rebuild? You save 20% VAT and do not need to compromise. You could even reuse the stone.

The cost of keeping the borehole / pumps / sterilizing will outweigh any water bill.