Mr Punter

I would want the plots to be separated with no shared driveway. I would not want neighbour vehicles turning in front of my house. All of the design and construction work will fall within CDM regulations and it is your legal duty to comply. You must have a Principle Designer and a Principle Contractor. I assume you are VAT registered?

Who supplied your front door @HerbJ?

You normally have compressible material in the movement joint. The render bead sits centrally on the joint with a wing either side fixed to the substrate. There is no big issue with the bit of brick. The gap could be filled with mortar, render or whatever.

Is it possible to dig a trench on the other side of the foundation and fill with shingle like a French drain to divert the water? With the joint, have you tried CT1? Otherwise could you loosen the screws and put rubber strip under the timber?

It don't see why the existing cannot be safely built over. I would want to know that the OSB or ply on the existing was thick enough to hold the proposed screws. The new firrings need to be very well fixed down, then the new OSB or ply would be best fixed through the firrings, so some very long screws needed near the apex. There is nothing wrong with having the additional void, as you always get one with firrings. I think it would just be a waste to scrap what is there.

You may as well incorporate dormers. You will need a scaffold temporary roof. The trusses will be big and heavy.

The tiling and flashing needs to be complete to make it weatherproof.

Could you do it like this and maybe even have it step in a couple of hundred mm?

Who did the design? At first floor level, why are there are four leaves of masonry and two layers of wall insulation? Also, what is the point of using the pumice and twin wall on the same chimney?

What are the outstanding snagging issues? I hope the crazy gap ridge tile has now been replaced?

No it wont matter as they will have render beads for the gap.

10-16mm is normal.

The use of the grinder at about 3 minutes was, err, interesting. Holding the grinder the wrong way round, nearly cutting the power lead and not securing the work-piece.

Yes. The heat will dissipate downwards.

We did a suspended ceiling in hollowcore and almost every core we drilled held about a bucket of water!

You could probably get a wire between the planks but you will struggle to go across them.

Imagine if the volume housebuilders did it the same as @NickB. There would be lots of very happy customers.

I have always been a bit suspicious about the rules on using the really annoying short twist nails in joist hangers. They seem quite insistent on it but with some hangers where there are loads of holes and no excessive loads I am sure that even dry lining screws would work fine. The fat twist nails are really easy to remove, so I think they could and probably do work loose but that is perhaps not included in the must stick to rules.

With 2 different foundation systems and on clay there may still be some differential movement. Perhaps design in some movement joints between the existing and extension. Stick with blockwork. Maybe use cement based weatherboarding?

I have been looking forward to this thread coming alive again. Please post pictures - good, bad or ugly.

Oh well, congratulations on selling it at last!

When they redo the render are they still looking at the Helifix crack stitching? It seems well OTT and if these are soft blocks I don't think they will work well. I think any settlement has already happened. The old render looks fairly well bonded. Maybe just a coat of RendAid and finish with OCR and masonry paint.

I think these are I joists, so a no-no.

In my limited experience the SE does the connection details. The fabricator produces fabrication drawings with more detail and you can get them OKed by the SE. Never seen an architect showing anything other than suggested steel locations.

I know it is just a simple case of measuring and setting the battens to the measurement but I would not want to batten a roof for others to slate, unless they confirmed that it was OK as I went.