Mr Punter

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.

You are probably in the best position to work out the completed value which will be between the semis and the bigger bungalows. I think you mean either 55 square metres or 550 square feet. You may be able to build this for £110k.

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!!