MortarThePoint

I'm expecting to have to leave the house alone for a week to 10 days and then only do non floor based tasks for another month after that. I guess an advantage of getting the sole plates in before screed is that the stud partition could then be assembled after 10 days rather than possibly waiting the extra month.

The next big step for me is installing UFH and screed. For the ground floor (GF) we have used 375mm Thermobeam which has a 50mm concrete deck over 325mm of EPS. For the first floor (FF) we have used 150mm hollow core planks. We'll be using an ASHP to heat wet UFH. We had to cut blocks to establish a good coursing on the GF as the Thermobeam height control wasn't very good and so that has pinched 10-30 mm in places. Consequently, and because we have 50mm of concrete as the next layer down, I want to use a thinner screed. I have been looking at Thermio+ which supports screed depths down to around 40mm (20mm above pipes). I think I am sold on Ahydrite liquid screed over the more traditional type, though am open to persuasion. The first floor HCF is much more level, but it makes sense to use the same screed throughout. I had wondered about forgoing underfloor heating on the FF, but we are interested in using the attic space so having two floors without significant heating seems a stretch. Again this would be around 40mm thick. On thing I was wondering was about stud partitions. Should these be established (or at least their sole plates fitted) before applying screed or is it best done afterwards on top of screed?

Will you have an opportunity to reuse the OSB later on? For example flooring in an attic space. If so bear that use in mind and I suspect the 11mm may fall short of what you'd need for the other use.

I've drooled over he Schuter Ditra Heat system as it has thermal decoupling as well as being able to accommodate substrate shift (e.g. concrete cracking) whilst being compressively strong. It's eye wateringly expensive though ~£16/m2 for the egg crate and ~£60/m2 for the wire which is frankly a joke by comparison.

That's right. Since then I bought my own wetsuit for open water swimming and have to confess that it's hard to do a 4 hour swim without taking a leak ?

Wowser!

My sailing club had a dustbin full of bleach to wash your wetsuit in and cold showers to be dodged on the way home.

Well I have had some numbers back from the truss designer: 2-ply truss 6.3kN (factored) 1-ply truss 4.4kN (factored) ? Must be all that snow on those two days a year we get here. That makes for a total load on a ledger board of 35kN which falls into my scary category. I phoned Rawlplug asking about options. They were very helpful and have since done some looking. "the concrete screw gives quite good loadings 2.3kN recommended load if you need higher loadings then you need to look at Resins". That's not a scary number of screws 35/2.3 = 15, so would be one every 300mm. He shared a datasheet which included this: I guess he is using the 8mm tension figure of 2.3kN, the shear figure is actually slightly higher. His email had a potential killer sign off though "There is no load data for concrete screws and bricks but we have used concrete screws into bricks and they work well the only issue is all bricks vary and it would mean doing on site pull out tests to prove the brick is suitable." My bricks are 25N/mm2 but I don't have the equipment to do a pull out test. I hate having to talk to by Structural Engineer. Of all the people so far, he has been the most difficult to deal with as there's always a vibe of "why are you bothering me with this".

Any idea what the energy consumption is? I expect the thermostat means it's only on a small proportion of the time, but what proportion I wonder?

I think I'm sold on UHF for the bathrooms, but inclined to go electric so that it is more immediate heat. I can have it heating up something like 15mm of material with a higher power than a water system would achieve. It does mean better planning is required in terms of when it comes on however.

It's a good name from the bill payer's perspective, but sets the tone with the family. Is there a KindDad range instead

If you have a link or picture that would be cool as I'm considering options. The most likely approach will be linking it to the home automation system that I am cooking up. I can then use a simple analogue thermostat that has its power turned on/off by a smart switch relay (e.g. something like Sonoff TH16). I'd be embarrassed to admit how many of these I have already as that's part of the day job ?

I asked them to include a 5.4m length of 47x222 with that in mind. I'm also getting some 47x147 and 35x147 as I had paid before then dropping an exterior area that I want to do in treated timber that they don't do. Do you think 47mm is too thick for the ledger board, do you think 35 would be better?

Is this the sort of thing: https://www.ebay.co.uk/itm/321589962068 Very low price (e.g. £40/£53 for 1.5m2 with a manual/digital thermostat, £57/£71 for 3m2). Did you use that digital thermostat?

Thanks @Gus Potter You're right I've only included a subset of the loads so it needs to have more consideration. I will ask the designer for the loads which he has been happy to provide before for some other trusses. In the meantime all I have is the hangers he has specified for use with a timber mounting, KH-75 and KH-38 rated to SWL of 12.48kN which is way over anything likely. For masonry hangers the area is a bit complicated by a transition from blockwork (7.3N I think, definitely no weaker) to brickwork. The bricks are thankfully frogged and not perforated and have strength of >=25N/mm2. The transition is a horizontal one at 2700mm above DPC and the top of wallplate is 2610mm which will also be bottom of bottom chord. A 225mm high masonry hanger would therefore go above the second course of bricks. That is all at odds some what with the sketchy guidance from the warranty documents. I could probably get the thumbs up from the likes of Simpson StringTie though. I also think a ledger board is an easier install for my set of skills. I don't fancy fitting a restrained masonry hanger as that would require removing the brick it sits on so as to get the strap hooked over. A 200mm ledger board could be mounted to have bolts ~50mm below the top of the highest block course (2650) and ~middle of the first brick course (2740). With the strap tucked behind the ledger board it should be capable of a far load.

I discussed it all with the truss designer and he has shifted the left hand vertical to allow the truss bottom chord to be trimmed to suit a ledger board.

What did you do by way of thermostats? Do you have them both on timers?

Would be painful to have to install the electric panel heater and not have then benefit of the heat pump COP as well as hidden heating provided by UFH

Is that a wet system or electric heat mat in the bathrooms?

Interesting, so the opposite of my thought process. You are obviously braver than me but it makes sense since cooler bedrooms are nicer anyway.

It's interesting to calculate how well coupled different areas within the insulated envelope are connected. In the extreme, I think I have worked out that if we had no first floor heating, it would only sit lower in temperature than the ground floor by 20% of the difference between the inside and outside temperatures. So that's an unheated first floor temperature of 16C when the ground floor is 20C and outside is 0C. It's a lot of effort to go to really for the benefit since all our living space is downstairs. It feels too brave to omit it completely though. Considering just the bathrooms however. Each has only 25% of its walls as external and the ceiling u-value is obviously massively better than that of the floor. If the bathroom was unheated, it would be less than 1C below the rest of the house when the outside temperature is 8C or higher. Below is the calculation where I have considered the heat flow* based on each surface of the bathroom 'cube': This begs the question of whether it's worth the effort. I estimate the cost of adding UFH to each bathroom to cost around £300. If you want the warm feet feeling, a 1.5m2 electric UFH mat just in front of the bath/shower could cost around £35. It could come one when the light turns on and draw 225W whilst running and cost £12/year based on 1hour per day which is a lot of bathroom time. That's a 22 year payback time which is pretty rubbish and the electric solution would be more immediate. Alternatively, just a heated towel rail adds some room warmth and warm towels. Is this the sort of thing that ends up a "Specification point" in that without it the perceived value is lower even if the reality isn't the case. It being hard to add later we add it now to satisfy the possible future purchaser. * Note: Q = Direction * U-value * Area * dT

Yes, I can appreciate it needs something. I expect it will be: Left wall --> ledger board --> truss bottom chord --> right wall So I'd need to add straps at both ends of that chain

Unless I can face fix the restraint straps or use a ledger board and notch it to accept the strap between it and the masonry I'm in for a world of pain. The modern straps are quite thin so perhaps I can just pinch it between the ledger and the masonry. I can't spy any restraint straps on this setup: http://www.fourwalls-uk.com/blog/category/extension/page/3/

OK, thanks because I do want to get it right