saveasteading

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.

Im thinking @zoothorn doesn't need to turn off the water as it is after the taps, before removing this part but it may be prudent? A spanner with a decent long lever?

I don't like the idea. An SE is the best bet. The steel has to be examined. Rust isn't always as bad as first impressions. But there are usually other options such as multiple small beams, additional supports or a wall underneath. It's going to be expensive. Some insurers reject on any excuse. All you can do when getting a quote is answer to the best of your knowledge, so reread what you told them then try again. You are all in this together. Have neighbours been below? Pictures would help.

Stop Press. I replied 'identical' but I was wrong. I've spent the afternoon comparing the Scottish and English reg's because I had a feeling that might be confusing me. The old fashioned way with a printout and a yellow marker. First appearances show the same rules, calculations and options, referring to the same document, and with shared drawings. BUT they are far from the same. I haven't checked out the implications of which is stricter yet but simply warning anybody who is involved at present.