Mr Punter

The EPC says you only have 100mm loft insulation. Top this up to 300mm and it will pay back very quickly.

Why not get some quotes for the gas combi and rads option and compare to the ASHP?

If it is broken you need to replace it.

Well I very much admire your persistence and wish you good luck.

Would it be possible to get the work done, as failing that they may all find themselves homeless, which will help nobody?

Well done for doing your research. Lots of people get hooked into thinking because they have waited a few months and spent 2 or 3 thousand, they are committed to purchasing. The purchase price is likely to be hundreds of thousands, so just write off the fees and be pleased that you have not bought a liability.

Just use https://www.timberbeamcalculator.co.uk/en-gb/span-table/floor-joists?load=1.5&class=C24

If the flue goes through other properties that you do not have access to it is not maintainable. If you are concerned about CGT on the sale you must have made a profit.

They will not be designed to take much loading. I would restrict it to Christmas decorations. Nobody wants to climb up and crawl around a hot dusty loft to retrieve a book.

It is worth noting that in many circumstances, installing a gallows bracket will not be satisfactory. Factors such as neighbouring chimney removal, wall thickness and height have an impact. Often a Structural Engineer will need to be involved. Corbelled brickwork alone is a no-no.

65mm is too thin for concrete and will break up. A liquid screed would be your best bet. I have used Cemfloor (installed by a contactor supply and fit) and it has a decent finish that does not require laitance removal.

How is that easy? It will need scaffold and will raise the height of the roof and affect fascia / soffit and abutments. Maybe I misunderstood you?

That is what I have. I used a chimney type extractor, took out the motor and connected to the ducting to an inline fan sited in a cupboard on the roof terrace.

You often see a course of thermal blockwork for internal walls and soleplate on that. It stops the soleplate being cold and allows for insulation and screed. Soleplate on slab is old school as it is cold and more prone to rot. Also if shotfired they often use l shaped soleplate anchors so as not to penetrate the DPC under the soleplate.

Beechwood Hall in Cooksbridge is clad using Sweet Chestnut. https://www.facebook.com/photo.php?fbid=871128391694956&set=pb.100063934084990.-2207520000&type=3

Slip ties may be better, with a sleeve on one side where you have a vertical movement joint in a panel. For tying to the frame, the normal timber frame ties will be OK.

If you are looking at a home grown timber, Sweet Chestnut is worth considering.

How about fibre cement planks, like Cedral or Hardie? I prefer the smooth finish. They need little maintenance and the finish is long lasting because the planks don't expand like timber. Also they are fire resistant. If you are thinking of fire treated timber you may need to have them pressure treated with Non Com, not just coated. Very expensive.

The top layout is 36m2, the lower is 64m2. Timber frame with blockwork skin would work OK and not too expensive. You would need building regs.

Maybe the shower could connect to the stack separately. The WC flush may pull the shower trap as configured.

18mm OSB should not sag if correctly installed on 400 centre joists / firrings. If the boards are defective, they need replacing. The grp is there as a waterproofing layer, not to make up for dodgy OSB.

Do you have damp in the floor, the walls or both? Where is the external ground level in relation to the inside floor? Have you checked for any possible leaking drains, gutters and pipes? I have seen the silicone rods and they seem a cleaner way of installing a DPC than the liquid, where it was hard to adjust dosage etc. Did yours fail? If so, did you follow the manufacturers instructions?

SIPS OSB I assume.

18mm OSB or chipboard t & g, edges glued together. Leave a gap of 10mm around the edges for expansion.

Half the diameter.