saveasteading

Quite so. I've just reread the original post. Concrete cracks, steels corrode. Newish walls can be removed again. The managing agents were not technical people, so their comments are probably irrelevant. So the residents' trust perhaps need to get a fund together and start from scratch. A good local SE will be a starting point. A free first visit for a quote. Then a solicitor (there are construction specialists) to formalise the process, get insurance etc. Then sort it. The value of all properties will then increase by more than the cost, esp for those who can't sell. OR. Is there a local big developer/ landlord who might buy the lot and sort it out... takes the risk and makes money?

To put it into real life context, in the Steading we left a significant proportion of 600mm original wall exposed internally. This was for aesthetics and a historical nod. That would never pass Passivhaus which is an extreme target. I have no intention of sacrificing lots of money and aesthetics for the certificate that comes with a few % energy benefit. But many do and it's their choice and money (never regained in £ payback). We did get respect from the bco who agreed it was a good design feature, and we balanced the insulation by extra elsewhere. You are building all new, so can more easily tweak the insulation. Should be easy enough esp with a proper analysis with expertise. You say lots of insulation. What products?

Premature use will damage the surface and make it too wet. Leave it too long and the surface dries before it sets. There are rules about not pouring in cold weather. But for hot it will depend on the mix, the thickness, time of day. I've never used sprinklers but I see the advantage as compared to single use polythene. Curing spray may be optimum.

Its not complex. A screwdriver which shouldnt go through, and a wire brush to remove the surface. More technically, a drill to look for inernal shiny bits.

Building control were fine with me using grano dust as the top layer. So they should be. Sand is often used far too thick to overcome poor levelling of the sub-base. Then it picks up footprints and other shapes which the concrete has to drag along if it shrinks while curing. This is textbook stuff apart from a couple of things which reduce your mark to 99%. Well done. 🏆

I think some presenters have something to sell, but they can't fill 10 minutes with the facts so exaggerate. The less they understand it the more they exagerate. It's as if those prescious but flighty heat particles were rushing through a piece of timber as if it was a big hole in the wall.

Yes it might be moderately simple but this is SE work. If we are to help further we need photos.

Whatever we build, it is a thermal bridge to greater or lesser degree. BH can sort this And carpentry skills will be of huge benefit to the final product even though the SAP doesn't acknowledge build quality.

I like the word 'just' there. Would it also creep into every corner under the floor and expand to put an upward pressure onto the floor, as in underpinning? But its certainly going to be easier than barrowing in the first 80% So that is a decent shout for the bulk fill.

Not something I'm familiar with.

A coal hole? It would probably be difficult to fill and compact after the first few feet.

He says you've failed but doesnt know why? He put the numbers in. It doesn't sound like an expert, just someone with a licence for a sap spreadsheet. I've come across one such. He wasnt interested in the reality and just wanted to enter conservative defaults. Your construction should pass but tell more. Insulation spec in floor and roof?

Simple can be elegant. The trouble is the method. Imported stone ( a lorryload) has to be placed in the basement and thoroughly compacted. Where would it be stored? That mean breaking out the floor. Would the stone all be barrowed in? Then a new floor. So that does have the advantage of simple support to your floor and added lateral stability. You would have to move out for a month minimum. Another easy solution might be to support the existing beam. A central prop means that the beam only gets 1/4 of the current bending. Or a masonry wall all the width, or a new beam. All needing foundations. Not quite as disruptive but still a month out of the house. Gut feeling £50k including fees and unknowns. Lawyers will take more than the Engineers. 25 leases, £2k each. PS. On second thoughts there will be redecorating, accommodation and likely more that we don't know about. For discussion say £100k = £4k each. Would they all contribute or some not be able to or want to?

@Nickfromwales it's a very big deal as liability extends to the whole block of flats. And might there be other basements? Who owns the basement/ void?

. It needs to be made clear that there will be no blame. Whoever is top of the pile is making the decision. Only that way does the designer bring up the 'crazy' idea from the back of their mind. Or the contractor says... if only we could do x, and the designer says there is a way but hadn't realised it was a practical issue.