Mr Punter

Could you stick on a bit of stainless steel? Maybe fill sand and paint the end?

I have not seen the whole design. How is the fall achieved? I cannot see any firrings. Often the adhered coverings need OSB to be stuck onto and there is none shown. I am not sure you could fix EPDM to Celotex. I sometime see the tissue faced insulation specified but it is very costly. I would make the upstand out of 63mm x 38mm treated cls with 9mm osb sheathing nailed to the outside, insulated with 50mm Celotex. Be much stronger than the tile batten and better insulated.

I fitted Airflow Icon fans with delayed start timers, so they do not come on if you only have the light on for a short visit. They do a mixed flow one which will easily cope with a long duct run. You can duct through the ceiling or surface and box in if the joists run the wrong way.

I am not sure what your threshold detail is, but I would expect the EPDM to lap up the 30mm at the bottom and almost into the room. The cill should be well bedded down on mastic and sealed to the EPDM. Even if you do not have much fall there is no reason water should be getting in. This seems like a combination of poor design and detailing and poor installation. If the water is coming in through the door, remove it and fit it correctly.

I would avoid damaging the cavity trays when chasing in the flashing. The very small amount of residual exposure on a rendered wall will not be enough for any water to penetrate. So the left hand looks good.

Really you need professional advice on this. Have a browse through the VAT section https://forum.buildhub.org.uk/forum/174-vat-reclaim-queries-guidance/, but pub to resi VAT rules are beyond a bit of light reading.

Hi and welcome. There are some complex VAT rules on conversions. Be aware of time limits on the sale for SDLT. Are you going to be hands on?

I have done sleeper retaining walls with C and I section (PFC and UC) structural steel and sleepers slotted between. No trench needed. Sink the steel at least 750mm in the ground and concrete in. Use some terram or similar membrane on the back of the sleepers.

New build is often cheaper per m2 than conversion. Obviously a lot depends on how well the current building is constructed. A fair few commercial buildings have far better spec foundation and structures than dwellings do.

I like the design. It looks quite expensive and has some complicated junctions but you have obviously thought it through. Any sharing of GIA and budget (excluding service connections and fees) would be appreciated but really I am just being nosey.

Not a clue about PV but I am really interested to see the project as it progresses. Will you do a blog?

They sometimes have a screw at the front at the base that winds the rear leg up / down. RTM.

I have seen studding with 20 degree twist over a 2.4 length. Sometimes it is so bad even short off-cuts are useless.

We used treated timber here and fixed the cheapo Screwfix Turbofix coach screws to the other side before fitting quick and easy self drilling with a decent impact driver. Concrete locks it all in.

As per @Vijay, threaded bar and resin would be better but as you already have the shield anchors, try them. If they start to fail, use the resin fixings.

@NSS has had this fitted a while ago and may be happy to share their thoughts.

The neighbours house looks very neat and tidy. When home "improvements" get bodged...

He did it all in a single sentence without full stops which may be why his is finished and yours is not. In addition to his full time job as well. I don't think anyone working for @nod would mess around. I would not last a day!

If the concrete is sound, leave it in place. Hopefully the tiles are non-slip?

It would be better and safer to make the hallway and stair protected. I would not fancy jumping out of a first floor window over 4.0m to the ground in the event of a fire breaking out on the ground floor. Have you considered over height or even storey height internal doors on the ground floor? They may look quite impressive with little additional cost. Big double doors opening into the hall would resolve the fire protected stair and also give the option of dividing the space / providing privacy so that your delivery person does not get to see the whole living area.

I thought IR heating was restricted to outdoor smoking areas, manned warehousing etc.

A floor plan with a North point and some dimensions would be helpful. Also target budget. The big slope up to the rear garden is a pain if you want to increase floor space in the main house. If you do not have plans and cannot do them yourself, get an architectural technician to draw some. Shop around, it should not cost much.

The suggestion by @DevilDamo seems the simplest and best. You would need a gallery landing to join the hall outside bed 4 to the bottom of the 1st to 2nd floor stair. Have the same landing / void arrangement as the first floor. There would be future potential to make this floor a master suite / teenagers / au pair accommodation and would be of value when selling. The sections you have do not seem correct.

You could also use stainless staples to attach some cheap dpc to the faces.