Mr Punter

VAT charged 20% on ours.

Give him a chase - email then phone.

I have a friend who does a fair bit of student lets and rarely has issues. They are jointly and severally liable for damage and repairs and in some instances also for the rent. In any case, parents are obliged to act as guarantor. The sort of behaviour by @pocster's tenants would be more in line with an emergency housing / hostel setup.

With the Velfac system the outward opening ali sash is the same size as the fixed internal timber frame, so if you rendered up to the window you would not be able to open it and nor would it drain correctly. Their detail is to render the returns first, then the window size is the render-to-render size minus 12mm per side and top, and 20mm for the bottom. The window is then fitted with a 15mm cill packer at the bottom and fitted in the opening. The gap is sealed with foam on the inside and Compriband externally. Double check all the measurements as it is easy to mess up.

To be fair to her she did well. She has a better aim than me!

Make sure that in the event of a blocked outlet the water will flow down the stairs, not through the doors.

The rigid full fill boards are a bitch to install and the chances are the brickie will lash them in however they can - upside down, wider cavity, gaps or whatever.

A bit of a change in the weather from setting out to pouring the slab!

If that is the finished value you will need to be very careful that your total costs do not exceed this. There are lots of areas where savings could be made but I think you may need a bit of a redesign. There is currently a lot of wall, window, roof (and scaffold etc) in relation to floor area.

How does the render work with the ICF? You could do the top bit in timber frame with an aluminium coping.

First fix one day for 2 chippies. Would take me 2 weeks. Would take @Onoff 6 months.

Done correctly it will have a door either at the top or the bottom of the new staircase and will have an escape window Velux or dormer. If it is not intended as a habitable room and is only classed as storage or hobby space, building regs are not required. If it is a bedroom they will need to have a completion certificate and failing that they must not advertise it as a bedroom.

And I assume there are bifolds running the length? If so, there is not much you can do. Put lots wherever else and make sure there is lots of ventilation through any cross walls. Oh and I don't know what system you are using but @Russell griffiths had some real issues on an ICF with the concrete squashing the telescopic vents.

No I have recently done a development with lots of external doors, full length windows and windposts and the number of place we could put vents was very limited.

Brighton introduced an article 4 direction for certain areas that they thought were overrun with students, so you need planning consent for HMOs https://www.brighton-hove.gov.uk/content/planning/planning-applications/planning-permission-houses-multiple-occupation

Is this a shared house, where the tenants know each other and are jointly and severally liable, an Airbnb, or what? How much is the rent? In nearby Brighton you cannot do HMOs without planning consent (which they rarely grant).

I read recently about their new Pilingmaster - can go 14m and 600 dia!!

A lorry mounted hiab would also do this. In the meantime just cover the holes with some osb or whatever to stop the rain. Don't cut it to size.

Is this for students? Do any WCs have Saniflos?

I have some tilt turn. They are useful to me as they can be cleaned from the inside but curtains, rails and poles need to be out of the way for them to open. You can fit external shutters though.

Just move the opening along a bit...

Looks neat with the trims around the openings. If it does get damaged by anyone you could use the downstairs dungeon to conceal the body.

Looks very sleek although I think I would be scared to use it. Will decoration, repairs or replacement of the cladding be an issue in future?

The mix sounds fine. You could use ballast instead. You may want to PVA the adjacent bits of slab. I would sort out any iffy connections and thoroughly re-test before concreting.

You could do either but I think 2 skins with 100mm cavity would be simplest. With single skin you will probably need 140mm blocks and you would need to insulate internally or externally.