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I'd be a bit concerned that the 10mm gravel may damage the ufh pipe as it is being crunched around on whilst being laid

Thanks @Nickfromwales & @JSHarris...I used to consider myself a reasonably intelligent person, but having read that thread I realise I am walking among giants! I think my floor slab will have fully heated by the time I absorb all that information.

At a guess it won't be "fully"* cured for at least 10 to 12 hours, but it'll be around 80% or more cured within a couple of hours. After 24 hours it will be around 90% cured, about as cured as it's going to get, anyway, in the short term. *concrete doesn't really fully cure for decades, as chemical changes continue to harden it through life, which is one reason some well-mixed old concrete is so damned hard to break up.

Any particular reason for 100mm screed and not 75mm depth with the extra 25mm going to improve your insulation depth. One sheet of 50mm to cover the first fix pipe work then overlapping with a 100mm sheet. Or build it to suit 200mm insulation if the budget can stretch that far.

Thanks for the kind words, and sorry if the low energy thing gets a bit much at times! I'm afraid I've always taken the view that you get out of life as much as you're prepared to put in, and that helping others, in turn helps them to help more people, so, with a bit of luck, perhaps it helps to make us all a bit more altruistic, making a sort of virtuous circle. This attitude does backfire from time to time, though, as I've had more than one person exploit my belief that learning, and then sharing what you've learned with others, is something they could exploit for personal gain. What really motivates me are the changes I've seen in my lifetime, from a society where learning how to, and then doing things yourself, sharing that learned experience with others, and taking pride in doing that, change into a society where fixing things, or making things yourself, are seen as weird hobbies, with the "normal" thing being to just chuck stuff away that stops working, go and buy something new, or pay someone to do something you could do yourself, without a thought as to how rewarding it would be to use your own resources and then pass on what you've learned to others.

I remember seeing this some time ago ..... American, but might be of help. https://www.youtube.com/watch?v=mmUJQHN7ALw

In the end i taped one side and clamped a bit of wood across tape. Did the same on all 4 sides. Offer window up first so you know how it fits. Offered it up took off clamps and slid it in hole. It worked sort of As i said earlier i didn't really know what i was doing

It was easier for me, because my compriband went onto the window frame, then I slid the EWI panel up to it, so even if it expanded quickly, it didn't matter as it just got compressed again. I take it you want to fit the tape, then put the window into an opening before it expands too much? If so pick the coldest day you can and early on in the day. It definitely expands a lot slower when cold. Forget trying it on a hot sunny day. One side of the tape is self adhesive with a peel off backing paper. As I say, I stuck that to the window frame. The fixing plates were on, but where I fitted the tape was forward (outside) of where the plates came to. Make sure your chippy has some suction lifters (someone will come along with the proper name for them) it makes it so much easier.

by the time i had taped one side the other had started to expand

@JohnW you have a similar floor build up to me but with a couple of exceptions.I have a 125/130 PIR going down with a 25mm EPS all round to absorb the lumps instead of sand a la @Onoff. My top course is a flowing concrete from a local supplier with fibre reinforcement in it - a polyester fibre - and a number of plasticisers that make it self levelling and self compacting. Target for us is 0.14, but that is a choice as we have a conversion element too and it won't allow us without a significant amount of work to get to a very low uValue on the walls so we've gone for a very warm "hat" on the build ...! Concrete flooring is probably the easiest part to get wrong but I've basically gone with it as it will make life easier. Is it more "dense" than normal..? Who knows..! Unless concrete is aerated, the mix of aggregate and sand to cement and water will make a very minor difference to the uValue overall.

@JohnW I am thinking that perhaps you need to be questioning that concrete screed. One question to ask might be by how much it increases the "thermal mass" over concrete. The not very meaningful answer is likely to be to do with the increased density - and I suspect the increase is not very much. The cost per cubic meter difference and the pfaffing involved in 2 materials means you may be able to fund a West End theatre weekend (or a posh meal out) to help you unwind from the difference while it starts to set. You can never have too many unwinding weekends.

We have a pretty standard "passive slab", which is also the foundation for the house. The under-insulation build up varies a bit with the type of soil, but in our case we excavated to a depth of 150mm over the whole area of the house, plus about 300mm all around. This was filled with type 3 stone (18mm to 35mm, no fines) compacted in layers until it was 150mm deep (so the same as the ground level. On top of this was laid a 25 to 50mm thick layer of coarse blinding grit, very carefully levelled. The EPS insulation was laid directly on to this, with L shaped sections all around the edges and the interior filled with over-lapping 100mm thick EPS sheets. The DPM was laid under the last 100mm thick insulation sheet. The steel reinforcement fabric was then laid in place, including a reinforced ring beam around the edge and for two internal load bearing walls. The UFH pipes were fitted, then the concrete was poured and power floated smooth. The whole process of laying the foundation to finished and level slab, with UFH pipes in, took 4 days. So, the build up, from the bottom, is 150mm compacted type 3, plus grit blinding, 200mm of EPS, DPM, 100mm of EPS then 100mm of reinforced concrete on top, with the 12mm floor finishes (travertine and bamboo) on top of that. It's documented in our build blog, starting at about this entry, with photos: http://www.mayfly.eu/2013/10/part-sixteen-fun-and-games-in-the-mud/

PMSL That made me laugh out loud. Good man!

As someone's already mentioned, "thermal mass" isn't a measurable parameter, has no units associated with it, and no known way of calculating what it actually is for any material. Concrete and screed are very similar in terms of heat capacity (defined as the amount of heat energy required per unit mass, or volume, per unit change in temperature) and thermal conductivity (defined as the rate at which heat energy flows through a given thickness of material for a particular temperature differential). There won't be a significant, or even probably detectable, performance difference between laying UFH pipes in the slab and laying them in a screed on top of a slab, in practice, particularly if the overall heating requirement is low, so the UFH temperature is also low. If the heating requirement is significant, say more than about 40 to 50 W/m2, then there may be a very slight advantage in terms of initial heat up time to laying the UFH in a screed, the question is really whether it's worth all the extra cost and time involved. My own view is that, for a well-insulated house, with a decent level of airtightness, and MVHR to significantly reduce the ventilation losses, then the heating requirement is so low as to make it not worth considering all the additional cost and time involved in laying UFH in a screed on top of a slab, especially as it increases the overall floor height build up and the screed adds nothing structurally. We have a 100mm thick slab, with the UFH pipes cable tied to the top of the steel reinforcement fabric on 200mm centres, so the centre of the UFH pipes is around 42mm below the surface of the floor. Our slab was power-floated dead flat, so the floor finishes (12mm thick travertine stone and 12mm thick bonded down bamboo) are laid directly on to the slab. This was a pretty cheap and quick way to get a heated finished floor.

Allow me

Nope

Afraid not. Along with plant and tool hire its chargeable

Bet you cannot wait for the sips to go up. Its Quick so don't blink as you will miss it. I went to work and came back with the ground and first floor up.

"I was GIVEN 34 sheets of 18mm OSB" Son of a....... Can you get me some mates like yours please? Cheers for the shed mini-blog btw ??

Done. SWMBO always said the only thing I did well was taking the p out of things.

Proaktiv called me up, they had quoted for full build and site insurance. They said they are not aware of anyone who would insure just things I order up so the only way to insure them would be for me to insure the whole job again even though the main contractor has insurance. I might just wing it.

It is indeed a good feeling when you have a builder that you know and trust. Mine was the same. I had worked with them before (I wired a house they were building) and knew their craftsmanship and attention to detail, and knew they had a skilled team that worked together well, and were very easy to work with. It will surprise some on here that I employed them without a written contract, just a handshake. I paid in stages in arrears so they put trust in me to pay for the work done, as I put trust in them to do a good job.

If you use Chrome download the Care your Eyes extension. A lot of dyslexic students use this to get the best background colour for their individual needs.

Finally, 'click'. I might now be able to explain this issue to someone else now.... a proper test of understanding. I'll start with my architect : a 'thermal mass' sinner.