saveasteading

Steel will be the answer. It covers big spaces economically. My rule of thumb is that adding an internal column under a portal frame will reduce that frame by 1/3 in tonnes and cost. What width of building do you intend? You don't want a column in the middle of your space I'm sure, so make this a fundamental requirement, and accept the cost. OK, so they should be able to look after you, and will be charging. So anything we say on here might concern them as distrust. Have you given them a budget? Would any of them know how to achieve it?

It doesn't have to be fancy special stuff. It is stopping fire from spreading through a cavity so even wood will usually be suitable.

a service void is nice to have but I'd prioritise the headroom. Anyway, that 830mm vertical bit could be widened to be a SV without affecting headroom.

I've done a few of these, design and construction, including a church, with the starting point being 'someone says you will be able to half the price we've had from tenders'.ie it's not a cathedral and so funds are tight. It is complex, based on the use, or variable uses, of the facility, and also the size. Ventilation can be a huge issue as is means of escape , if the numbers are large. Even which inclination of church and their procedures can make a difference to performance and choices. But to start with I don't know what you mean by a Composite deck screed. Does that mean your own steering group, or are there professionals advising?

it would be consistent with what is there already, but not really proper. It would be quite easy to redirect the round pipe to the grille with use of a hacksaw and a new connecting piece.

Understood. The square shoe isn't quite long enough and the round pipe misses slightly. If you can rotate the round one at any of the joints to be over the grille, that should sort it. For the square you need the tiniest length of pipe. Temporarily cut a detergent bottle to make a channel and slide it under, but leave the bottom on to make it flow the right way onto the grille.

I have a similar but worse situation where the grille is set 100mm below concrete so fills with leaves. It is an unpleasant chore to remove them. So I have made a chicken wire cage to hold the leaves back a bit more. It's not pretty. But I have also bought a small, battery powered leaf blower and am pleased with it. It makes it quick, and not unpleasant, to shift these leaves and others nearby. It is very battery hungry but OK for a 10 minute job even with wet leaves.

What width is exposed?

Per board or m2? At present my best price for 100mm white eps is just over £15/ board of 2.4 x 1.2.

Depends on the "STUFF". If it's a 1mm sheet of metal then water and air will get through so special screws have special washers that bind to the thread. A screw into timber might allow damp but not air through...so perhaps a smear of mastic is worthwhile. Yes through wood has been compressed so is tight, but could get damp. If you look at screws into cedar you can see that damp has got in.

It's BASF so not likely to be untrue. I've found a thing saying the eps nodules work identically, being bubbles of air, but the conduction route over the bubbles' convoluted path is less conductive because infra red gets mirrored back whence it came. Hmmm. Anyway its quoted insulation is 10 % better than white eps, but I think the publushed cost is double, and I wouldn't expect so much discount.

I'd have to check the facts but I recall that there was more than one factor, one being that a fire test sample was 'adapted' to perform better.

I wonder if it is hyped the same way as Multifoil, ie tested in a particular context then sold in another. A reflective surface only works if there is somewhere to reflect it to. "Graphite is a good electrical and thermal conductor".

I had completely misread that photo. I've now got it on a big screen without reflections. Forget what I've said and I will start again The crack is slightly concerning and may need repairing. So I suggest you ask an SE to advise. I think an over-plate of ply will do the trick but it needs to be seen in context and up close.

For other readers, it is indeed a real and a very bad possibility. I have been there when it happened. Our subcontractor didn't tape the joints properly. Our plumber had insisted on doing everything from insulation up. and it was the only time ever that we relinquished control of the slab concrete. It must have been 20 years ago and he insisted he was experienced and that it was fundamental that he had the package. I became wiser on that day, The pump-mix concrete got under the PIR which floated up to the surface. Suddenly I became the only person with a clue what to do, and I had them 1. stop pumping. 2. bring in concrete blocks, tread the pir down and lay the blocks on them. after about an hour the blocks came out and levelling continued. There will still be a skin of concrete under that pir, but it all turned out ok. In hindsight I think they taped the joints in the dpm but either not properly or the concrete was spouted at an overlap and forced it off. Plus there wasn't an edge detail (the edging under discussion here, did not then exist). it was potentially very horrible, and the need for sealed laps and careful pouring was demonstrated. Thus I will supervise and inspect. Maybe I will do the first room myself to test for any difficulties. Any recommendations for a good sticky tape?