saveasteading

It's all pricey. Block and beam is a good option and not esp costly. Where you say slab, it's probably a screed. Miles cheaper than a structural raft.

Only if you have real doubts about competence. Without full reading back, you are on virgin clay? No fill? So it's straight forward and my decision would be in comparing a structural raft to traditional build of footings and slab. Beware, that the term raft is often misused, being applied to normal groundbearing floor slabs ( to make it sound fancier?)

It's all free online by NHBC if you want to do your own assessment.

Fair enough. It is not clear in the regs so it is interpretation. Neither is there anything to stop a neighbour planting an oak close to your house (I think there should be) , so at least this is on the safe side. The thorns aren't an issue but maple is. It's an easy assessment off a graph. Sometimes a designer will work from the closest distance tree to house and specify that depth all round.but it could be shallower at the opposite faces.

No, I hadn't seen the skirt before and it does look useful. The first UFH I was involved with was 20 years ago and the PIR all floated up even with concrete , not screed. Poor taping I think. An exciting day. Hence I take this very seriously.

OK found it easily enough. £1/m for 100mm.They all seem to call it expansion strip but it isn't. It's for containing the edge and free contraction in curing and as a thermal break. If screeds expanded and shrank significantly in everyday use, there would be a lot of broken tile and rumpled vinyl flooring. Our project has about 200m of internal edging, so I think this product will be worthwhile. We have to use something and this will be easy and provide a little thermal benefit. So thanks for the exercise!

Against the internal stud walls you don't need much insulation. Heat is 'leaking' into the wall from both sides. But you are then losing heat from the wall down into the slab. Timber is low conduction but not ideal. But stuff the stud with insulation and I think it is sorted. But you do need an edging to contain the screed. You can use the foam board as suggested and it will insulate between screed and timber where there would be some heat loss. In summary for best insulation, use that edging board and also stuff the lower cavity. Caveat: I have somehow missed the edging board in years of being interested and doing 3 heated screeds. What is it called and is it expensive?

I can see the logic of choosing it along with a contractor experienced in it. But otherwise I'd use whatever is normal locally The basement is not building but Civil Engineering so both SE and contractor need to be expert. By piling I assume you mean sheet piling to retain the earth while digging and building. What structure are you allowing for the basement?

Being wider (deeper?) Using a board cut to size would make it easy to cut and fit to the finished level as your screeding line. OK so that stops the floating. So I'm guessing the product is supplied as a standard width, then you slice off any that's above the finished screed. Seems quite complex. Is it expensive?

It is an edge to the screed , otherwise it runs into your wall spaces. That could as easily be hardboard or osb or dpc. Screed shrinks so it isn't for expansion, but does provide a clean edge and some freedom to move and limit cracking. If it is against block then an insulating material is advisable. But in the pic above, heat moves into the wall void then through the timber so it would be prudent to stuff the space with fibreglass or similar. In that picture they have not (yet?) taped the pir to the perimeter so grout will get under and it may float. I don't know what the polythene is for, or why it is being taped down. Anybody?

I think you have a good point. If built as your first picture, then the heat is travelling from the screed horizontally through that thin isolation strip, and into a masonry wall. That block wall presumably sits directly on a footing in the ground. So increase the heat resistance of the strip by thickness and choice of material. Eg 25mm of PIR instead of the thin strip of something as shown. On the other hand, the surface area of screed to wall is minor as compared to the lower face of the screed. And heat loss through to earth is much less than with exposed surfaces.

Too vague a question, apologies. I meant are you against Nutrient Neutrality,, (which I admit never having dealt with or researched) and, if so. why.

And colour , inside and out. It can be a long process from enquiry to order and it's easy for errors to creep in. Also check for the correct VAT % according to the circumstances.

In Engineering terms this isn't as worrying as you might think. Water in the pool weighs 1t/m3. The ground around it is heavier. I would expect the new foundations NOT to be deep so that the pool is unaffected. Are there technical drawings of the pool walls? But construction is the issue, and the need to not damage the pool. So standard or shallow foundations would be the aim.* Keep the extension design simple, such that it can all be carried or barrowed. Excavation may have to be manual. The very biggest concern would be that any future issue with the pool would be blamed on this work. But if the pool is your own, then that isn't a worry to you. An SE will handle this readily, and will also advise on how to build it so the pool is unaffected. Your builder has to be careful. @Gus Potter may agree or disagree. * loads do not disperse at 45° but it's a decent rule of thumb. If you know where the pool footing is, and draw 45° out from there, then do the same for your extension, if neither line cuts through the other structure then it's looking OK in Very, very approximate terms.

A quality window contractor will minimise the gap, and the amount of filler/ foam needed to fill it. Even the best builder will have wobbles and variations in the opening, and that quality window contractor will insist on measuring. They will also use expanding tape to get a good closure that will move with the building , not squirt stuff in after.