Mr Punter

It is a pain to fix counter battens through thick sheets of insulation to a roof as you are aiming for a rafter less than 2 inches wide and about 5 inches down. The fixings will be 160mm and need to be corrosion resistant. May be better to go for most of the insulation between rafters and, say, 30mm underneath, taped with ali. Easier and safer to fit.

Well done for getting the roof fall towards the outside. Much safer.

Depends on budget and current / required finish. Floor paint is cheap. Porcelain plank tiles are hard wearing and look good.

The paint is really expensive and you have to coat it lots. Doesn't' the ceiling give it 30 mins anyway?

Firstly, well done to your builder! Probably less than 1 in 10 would offer these options. I would go with option 1 but perhaps negotiate on the money. Option 3 seems a bit of a bodge. They will need to penetrate the existing membrane to fix the firrings and new deck.

Unless the existing structure is showing signs such as cracking, doors and windows not fitting etc. the existing footings are probably OK for what you propose. A trial hole later will confirm.

@recoveringacademic what is the external wall finish? It may be that this needs to be installed before sealing the windows, which can be done with Compriband or mastic. Compriband is vapour permeable so I understand that this reduces the risk of condensation forming between the window frame and the wall. An airtightness tape sealing the window to the wall structure on the inside reduces the risk further.

The windows were Velfac. IdealCombi do a similar looking system. The doors were another make. The lower part of the windows was obscured due to planning / overlooking constraints.

Do you know what materials you want this to be constructed from? Do the louvres need to be variable or fixed pitch? Do you need access to clean the windows? I can't see why these would be tricky. Can they not sit on the ground at the bottom? Have a chat to several potential suppliers then send some drawings to price. Get the price to include detail design drawings and better to do supply and fit. If the cladding is not yet complete all the better as there may be more fixing options, but this looks like a second fix item to me.

We did these horizontal ones in powder coated alluminium. There is a bracket at each end and one in the centre behind the slates which fixed to the outside of the timber frame with several coach screws.

Although it can make sense in a commercial building to have a main service duct / core, for individual houses the service runs are more ad hoc per service.

Often the people supplying the MVHR unit will do a plan showing unit and duct locations. They can also do a take-off of what ducting / connectors you need.

It is worth being very careful that your warranty provider is on board with your proposal if you use external insulation on a timber frame without a cavity. The Diffutherm system (no cavity, like @ProDave's) BBA states: "NHBC Standards 2008 In the opinion of the BBA, the use of the NBT Diffutherm External Wall Insulation System for use on Timber Frames, in relation to this Certificate, is not subject to the requirements of these Standards." Where the ventilated systems all state something like: "NHBC Standards 2016 NHBC accepts the use of the Jubizol CR External Wall Insulation System (Timber), provided it is installed, used and maintained in accordance with this Certificate, in relation to NHBC Standards, Part 6 Superstructure (excluding roofs), Chapter 6.9 Curtain walling and cladding."

A lot of the systems I have seen have a drainage channel between the insulation and the timber frame sheathing, which I would have thought would not be great thermally. If you choose to do this make sure the system has a BBA cert and that BC and your warranty provider are on board.

If it just sounds hollow, it may be fully adhered over much of the tile, so I would either leave it (preferred option) or break it into pieces with a sharp blow in the centre. What adhesive did you use and do you have UFH?

We used pink mesh cloth. You apply a thin coat of LAC and bed the mesh in while it is still wet. You can get very thin corner beads as well. On one plinth we did the LAC / mesh cloth, then tiled with slate strips fixed with tile adhesive, which looked quite good.

I have used Weber LAC. First thin coat with mesh bedded, then second thin coat floated / sponged to a sanded finish. It sticks to anything. Paint with masonry paint.

It is a bit annoying they didn't use 1:60 firrings but it won't make any difference to you. The roof will leak if the membrane fails, whether the fall is correct or not. Correct membrane install and upstand detailing is what is important here, not fall.

No. They are more expensive.

Brickwork often works out a much cheaper option for external skin.

If you have space and one of the TF crew can drive a telehandler this may prove more useful and cheaper.

You may want to consider demolition of the existing building. This will free up some potential design restraints, make the construction simpler and you will be able to reclaim the VAT.

Tilt turn are good on upper floors as they can be cleaned from the inside. Downside is they will clash with curtains or blinds. To clean outward opening windows from the inside you need either top hung reversible or side guided, where the hinge slides towards the middle of the window to allow cleaning.

The people we use do outline and elevations of the nearby buildings as well which is helpful in setting out and if you need context elevations. The survey information forms the basis of all other drawing information. Later we get them back to set out on the foundation concrete the corners of the walls, the centres of soil pipes and steelwork, wind posts and baseplates, all marked with a Hilti pin. They are very accurate.

This is something that makes sense but I never see it happen on site.