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No, house will be wet underfloor. It won't be cheap but as we are currently in rental we will be saving enough not to worry about that. Also, given that we have a lot of insulation in the Pod I'm hoping that it will not require too much heating!

So are you planning electric UFH in the house? Sounds expensive to run.

Had a tiler come and look at a job today. We have a 22 sq.m. pod that we are building to live in whilst we build the house. The Pod is a test bed for the house build and so the tiles we are using are 1200 x 1200 x 20 limestone as planned for the house. We had planned to tile the Pod ourselves but when the tiles arrived the other day this option rapidly disappeared when we realised how heavy they are. We are planning to use an electrical UFH mat and the tiler seemed to think that this should have a screed over before tiling! I have installed an electric UFH mat in our previous house (under slate tiles) and didn't take this approach then simply sticking the mat down and tiling over. Any views on whether this screeding idea makes sense, is the normal way to do it or are they simply making more work than is necessary? Thanks

Have you bought a heat pump cylinder, or a regular cylinder?

Hi @Nickfromwales and all, I get that you want me to fill the cavity with concrete. But have some concerns that mean I don't really want to do that. The DPC is above the bottom of the door cill and has been stepped down to run under the door cill. Note the door is only a single door so the reveal is 890mm wide only). So the cavity wall below the floor level is below the DPC. It has grey jablite type insulation in it. I was able to pull one piece out to have a look and found there was some moisture at the bottom of the cavity there when we had very wet weather. Clearly some moisture from the ground/hardcore outside the door can work it's way through the outer leaf to the bottom of the cavity when it rains a lot. The jablite was used at that level rather than PIR because it can cope with any moisture better. So I don't want to remove the inner celcon leaf (which would be complicated now the rest of the floor is in now anyway) because it would remove the cavity 'protection' from damp, and the jablite insulation. The inner leaf is also thermal blocks and provides a point of support for closing the cavity with a board over. The cavity is also probably 450mm deep there so would be quite a bit to fill with concrete and have dry. The fundamental problem is the lack of any support on the outer leaf side of the cavity, and the fact this is difficult or impossible to access with power tools because there is only the 100mm cavity to fit any tool into. Therefore my proposed approach of bonding a support piece to the outer leaf, which also has to be insulative. To deal with the stilhetto issue I am now thinking I could put 6mm No More Ply cement board over the 20mm XPS backer board to provide more rigidity and spread any point loads. (Not sure on the best thing for bonding the two together ? No more ply adhesive ? flexible tile adhesive ?). Then the. cementitious floor leveller should go on the top of the cement board quite happily. New diagram attached. On my test piece I bonded the XPS support strip to the concrete outer leaf with Rawlplug bonded anchor R-KEM 2. Chat GPT is suggesting there might be better alternatives to use for bonding XPS to concrete - thoughts. The biggest risk would seem to be this support debonding down the line. (I have some metal angle brackets but there is no way to screw them into the outer blocks.) More thoughts comments please as I need to close this out nowish.

If your anywhere near there on a new build, something is well wrong. UFH the parts are cheap enough. Your heat pump doesn't need to cost much either, mine was £2100 including VAT, you can claim the VAT back on new build. I would do a direct cylinder and just do cheap rate water heating, a cylinder is about £500. Then it's a matter of sourcing the fan coils. One in each bedroom. If you want to run fan coils at low temp for cooling you need condensation drains on fan coils and an electronic mixer, other option (the sensible one) run it at same temp. Your most expensive bit is the fan coils. If that's the fall back, why are you being anal about cooling - be pragmatic install A2W simply as above and actually have cooling. (Don't bother getting ripped off by a grant scheme)

blockwork looks much better this time!

I think i'd be digging out the pea gravel, bedding and surrounding these in lean mix concrete. Possibly a 25mm bit of eps where the pipe joint is to allow some movement. You don't really want the ground at the edge of you slab settling.

I do it on almost every job. Doesn’t dry the trap out, that’s a wife's tale, as you’d only do 2/3 of the dead end of the tray anyways; when you turn the shower on the hot water almost instantly warms the remaining 1/3, and the UTH is a 1/3 of the tray away from the trap. ”Do it”. 🫡🙂

Do you need a condensate drain in the wall for these air cons and fan coils presumably?

Traditional dab is fine. Lots of smaller ones, vs a few bigguns

Im Midlands so hopefully a bit more reasonable. If we exclude the price of UFH and manifold from the equation. I imagine I will have this whatever method of heating I choose. Also I will partially DIY this with either a plumber to connect up the manifold or both of us for the day to do the lot. Likewise can probably exclude the cost of cylinder as again will be fitted no matter what. So if the rest is 15k and can get the 7.5k grant then I suppose it's not too bad. If it starts getting up to 20k upwards or 15k and no grant then i would seriously be looking at a gas boiler (if SAP allows). Boiler installation, exc UFH and cylinder would easily come in below 5k supply and fit. Ideal world i'd like something like the Samsung option but like others I suspect it's pricey. I had a look at fan coils tonight online and the Daikin wall mounted ones look just like the aircon units. Are they just not as effective if powered by A2W instead of A2A? So if we say I was happy to spend 5k (guesstimate) on a couple of aircon units and a traditional boiler system would be 5K (all excluding UFH and Cylinder) then 10k is my baseline. If I am getting 7.5k grant back then I can look at spending around 17.5k on a system and still be happy. That's my man maths anyway.

Maybe so called under tile heating with electric elements just for the 10 mins you're in the shower might be an option.

I think it's a good idea. More comfortable, dries the tray (slightly) faster. The UFH pipes will only be at 20 something degrees so I doubt they'll have enough punch to dry out the trap.

Yes. You can put some polystyrene round to protect it a bit if you want. I remember digging a foundation by hand years ago, and coming across the storm water drain, then the foul drain below it. Both were encased in concrete. I had surround these with polystyrene, then reinforcing rods before the foundations for an extension were built. I was a teenager at the time, and my reward was a new stereo 😀 You'd think I would have learnt my lesson before building a whole house nearly 50 years later

Tile adhesive or traditional plasterboard adhesive? The wall is brick with cavity.

As an update, we finally bought a Kress 4X4 version and it's a cracking bit of kit. Can climb up slopes that I slip on. The only problem is the software doesn't allow it to drive up a 1.5m high brick walled walkway which is only slightly wider than the mower. Hopefully there will be a software update soon.

Really awful bug. Chat 5.5 thinking kept patching and we kept rolling back. I kept trying to think of other ways to deal with it so we can try different approaches. Been at it for 45 minutes. Rolled it back. clicked "pro" gave it all the info I could. Pro then thinking for 14 minutes!. Found a really obscure issue - MAGIC! FIXED!

Dont trust any of the AI firms.... Apparently GLM5.2 local is really good - of course hardly anyone can run it ....

Wouldn't put it past them.

It depends a lot on location (installers in expensive property areas charge more - somewhat justifiably as they no doubt have higher living costs themselves) However I'd be very surprised if you pay someone to supply & install A2W, UFH, 5 FCUs (and a DHW tank right?) for less that 15k. Not in the south-east, for sure. When I tendered my reno (in 2019) my builder quoted 8k to install just one ducted FCU on its own - without any A2W or plumbing work! That was obviously a throwaway quote for work they didn't want to take on, but still... FCUs are still not much loved in this country. If you do non-ducted / wall mount fan radiator it's probably a bit less. A decent bit less if your installer prices it as just another radiator install. Cheaper to install, cheaper to run, or ... ? If self-installing it's almost certainly the cheapest way to get heating and effective cooling. I contracting out, too many variables to say Running costs - probably the cheapest option, considering reduced maintenance load vs 2 systems, and esp with the increased TOU shifting that UFH allows. I'd always say put the UFH in, if you're doing some sort of GF slab that would accept it. Even if not connected it gives so much future flexibility. Specifically, UFH in a well insulated slab is both ideal emitter for renewable heat sources (very low flow rate), but also doubles as a large heat battery (storage heater) so you can heat it up during cheap rate and coast through the peak period. A2A really can't do that .

Anyone wanting to reasonably accurately calculate rebuild costs surely?

Maybe of interest to some people here, that would like to be on modern TOU tariff but can't get a smart meter due to lack of DCC coverage https://www.ispreview.co.uk/index.php/2026/06/chameleon-tech-uses-home-broadband-to-solve-uk-smart-meter-connectivity-woes.htm Technically not that different to what the Octopus Mini has been doing for a few years, except it sends the data to the central DCC so is supplier independent. It will continue working when you change energy supplier. Sadly it also lacks the handy MQTT interface of the competitor Glow Display IHD+CAD. There are some fairly absurd consequences of all thise: 1/ Despite being electricity supplier agnostic, this will likely break when you change internet provider (due to this industry wide failing that for most people, changing ISP changes the WiFi access point and changes default credentials to that WiFi) 2/ A rural property might: - fail to get coverage of the national DCC (despite gov funding to build it and a big drive for smart meters) - fail to get wired internet (despite gov subsidies to rural areas, and building regs requirement to prepare the house to receive it) - fail to get terrestrial wireless 4/5G coverage => Ultimately have to fall back on a foreign owned and controlled satellite internet provider to connect their smart meters to the supplier. Lets talk again about critical infrastructure sovereignty.

If doing as above the normal thermostat doesn't comply as it has to be non self resetting, a dual function cylinder thermostat would comply or a stand alone non- self resetting one complies That is indeed one way to achieve compliance, but not the only way. From G3 Regs The selection of safety devices should take account of the physical location of the devices, and the design, confguration, location of components and performance characteristics of the system to which they are attached. 3.18 An acceptable approach might consist of: a. a non self-resetting energy cut-out to disconnect the supply of heat to the storage vessel in the event of the storage system over-heating; and b. a temperature relief valve or a combined temperature and pressure relief valve to safely discharge the water in the event of serious over-heating. Alternative approaches to this are acceptable provided that they provide an equivalent degree of safety. Unvented hot water storage systems – systems up to 500 litres capacity and 45kW power input 3.21 If an indirect supply of heat to an unvented hot water storage system incorporates a boiler, the energy cut-out may be on the boiler. Narrative from me. As a heat pump cannot achieve high enough temps to allow boiling of the water (even R290 can't get hot enough) a primary control is there by default. If the heat pump uses an inbuilt immersion that immersion has to have a non- self reset thermal cutoff to comply with regs For the regs a heat pump is a boiler. Diverter valves - To comply with G3 Building Regulations. When installing with an unvented cylinder, Port A must be used for the hot water connection to the cylinder heat exchanger and Port B for the central heating connection. This means the valve when de-powered shuts the flow to the cylinder.