Mr Punter

The 22mm is annoying but is only 1mm per metre. With the sub structure stuff it will be possible to rectify but I would point out that I expect it built as per drawings. Better to let him know as he progresses than after he has finished. Check the drawings each day and go through with him in the morning where you think he might mess up.

I am hot on avoiding on high risk / severe consequence incidents, so falls from height, buried in a trench, brick on your head, crushed by materials / machine etc.

Timber frame stick built with mineral wool insulation and 18mm OSB internal sheathing. External cladding of your choice. Strong, simple, lightweight and cost effective. Pitched roof would be my preference.

We have used the Kytun Ali trims on natural slate. No issues with slate / slate and a half.

I have not used this one but have been able to get an email address to send Build Zone documents in the past, as at the time their portal had file size limits. Call them and ask what they suggest.

Have you been in touch with the tilers, or was this DIY? I have not used fix-a-floor but there should not be problems with the tiles over such a large area. If it were me I would do a small area and monitor before taking on the whole floor.

You did well to ditch the green roof. Unless the planners included a condition that the house could not be occupied until you have written approval for the roof as built there should not be an issue.

If it looks OK then it is OK. I have a property where the floor slopes 50mm over 1200mm. You only really notice when you look at the plinth.

I understand that Sweet Chestnut is a good durable UK timber.

If you are on clay soil you would need to excavate a vast amount and backfill with the granular permeable base material. You may need to go down half a metre from the finish level. I have laid permeable paving on a fairly thin bed of granite chippings on chalk subgrade and it drains very well.

The boreholes should not be too costly. If they are good designers they may use the information from the geotechnical report for a more cost effective solution for the pool.

Another vote for adding more battens. Just remove any that really mess up your gauge. The extra battens will strengthen the roof a bit. Could you get different shingles to work?

Well you could have a quick read of:

Estimators online are OK. You will need to send a full set of drawings and spec.

You can fit the frame into the timber studwork.

Whoops!

If you go wall hung, get the pan and frame on site before you set up the pipework, as the height of the flush pipe and pan connector are important.

Only the timber cladding would be a concern, as well as the "composite" if it is flammable, especially if the breather paper and sheathing are also combustible.

With timber frame and timber cladding you will not get decent fire rating without further protection such as boards or coatings.

For brands, Dewalt and Makita are good but cheaper brands like Erbauer and Titan can perform well. You will need more than one decent capacity battery and make sure it will fit any other tools you are considering. Go for 18V and batteries at least 3.0Ah. If you get stuff from Screwfix or Toolstation it is easy to return them if they fail.

spirit level accuracy not required but obvs the fall must be in the correct direction.

Be interesting to see the as-built version of the drawings. That is a lot of different products being applied at the substructure level. The insulation could be held in place with wall ties, although you could just use blown beads.

This could be a good application for Compacfoam, so after you have cut out the screed and removed the insulation you can infill with Compacfoam and sit the staircase plate on that.

Get in touch with your floor beam supplier. Tell them the weight of the staircase, the size of the footplate and the type of blocks you used. If they can't give an answer your SE will.

It does look a lot better as a house than a bungalow.