Mr Punter

It looks like one of your runs starts outside your plot boundary. Also you may need to be careful with scaffold and eaves overhang with the neighbours. Roof area looks about 50m2

You cannot use the combination of rise and going. 2r+g must be between 550 and 700 Reduce the rise and add another tread or two. 2400 for first floor ceilings is a bit mean.

Basements are fairly high risk and you need to consider ground conditions, safe excavation, ventilation, daylighting, retaining walls and waterproofing. Given the FRA I am not sure why you would bother. You would need a minor material amendment application for this. You could only use the basement for non-habitable purposes - cinema, gym , store etc.

You can get a tray like that which is only 30mm deep and sit it on the concrete. You just need to box out the bit for the waste. You not notice the 30mm step. Get one that is slip resistant and easy clean.

For timber , concrete and steel beams or joists on a residential project, 4m spans are fairly economical. Much more and it is worth looking at additional midway support.

The joins need to be filled to achieve the fire rating.

That is a very good price. What was and was not included?

I think you could get it for £22.5k but you may have to mess about with just using their approved installer. Yours are coming out at about £1,000 per m2 and you should be able to get similar for £700. You u values look a bit crap too. Get a proper window schedule done and use this to shop around. You don't need to get all from one supplier, so you could have doors from one and windows from another. Have you tried IdealCombi?

I think you will need an engineer to check the design. They may be able to advise where you can economise with materials. Will your welder do all the required fabrication? Here is one we had made and it used a central rectangular section. You could do similar and use 2 sections spaced apart a bit which would help stop any twist.

They are a real pain to deal with in my experience. They keep on phoning you.

A very interesting idea @edsr Regarding how this is structured, have you formed a ltd co with shares for each potential self builder? Already allocated plots? Worked out SDLT etc? What if you don't gain pp or shareholders want out or die?

Nobody dies from that

Tape the edge to the celotex, as well as taping the laps.

I think the 600 x 600 are a good call as there won't be too many grout lines. The corners are often the weak points. I think some of the tanking systems have tape that you can use. Make sure everything is completely dry before tanking.

I had an email from one of our contractors saying they had changed bank accounts and could I pay the outstanding invoice to the new number. We phoned them before paying and found their details were unchanged and it was an attempted scam. I think banks are trying to clamp down on this fraud by making sure the payee names match, whereas they currently only look at the account and sort numbers.

Just had a look at the SageGlass site. Very impressive. Any idea of the per m2 cost? It looks jolly expensive.

I'm sorry. That is a shame as I like the design. Can you find out the actual planning reasons for each of their grounds and perhaps modify the location or show in context / justify or modify the materials etc? Often a few small compromises is enough.

I think if you fully foam around the windows and have a quality sealant between the render and frame, plus an air seal internally from frame to reveal, there should not be an issue. What type of windows are you having?

My first thought would be to reduce the amount of glazing as a wall be be cheaper and more thermally efficient without glare. If the architect is any good you will still have loads of natural light and the place will still look sexy.

If you are fitting the windows up to the existing render I would just foam the gap between the masonry and the frame and run a small bead of sealant between the edge of the render and the frame on the outside. Compriband not required.

Good idea. If there is an external breather paper you may want to make this fire retardant too, as lots of those membranes really flare up, especially in a strongly ventilated cavity.

I am sure many people don't do any prep on liquid screeds - certainly not many developers - but they should be sanded and primed if you are tiling.

You don't need to do any prep before you tile it and if the screeder is good it is smooth and flat enough to lay any flooring (LVT etc) whereas sometimes you can get little ripples and bubbles with liquid. https://www.ukscreedsltd.co.uk/preparing-liquid-screed-floor-tiling/

If they are good I would have sand cement. I thought 70mm was standard, not 60mm. Does it have fibres?

I am not sure that it is big enough for access. Maybe only 450 x 600 which is too small to work in. It may need proper rings.