MPx

Not helping your question I'm afraid, but I have one of my own for you. We would have liked a wood burner in our Passive std house. I never considered the issue of the flue and combustibles...we canned it on the need for airflow to the fire. Is the MVHR capable of supplying enough air to meet the fire regs? Last time we fitted a woodburner we had to have an enormous air brick put into the lounge wall to get the installation signed off - not really on in PH!

Interesting - actually taking action against "cartel" like activity. On the other hand, the further I've gotten into self build, I simply don't understand how building houses is a viable business even at their inflated prices. On our last one (sold mid 2025) we broke even if you ignore 10 years of inflation and all the free labour - so a massive loss of wealth in reality - glass half empty ; or we lived in luxury rent free for a decade - glass half full? The current one is shaping up much worse. Looking like it will cost approx 150% of its market value to build despite me doing everything for "free" post water tight shell. Doesn't bother us as we do it for ourselves and have exactly what we want (which is the entire point of doing it) - but we have realised some understanding of why new builds are thrown together with appalling quality when you see how cheap they need to sell them vs the costs of build and materials.

No sure how relevant as I think it will be material dependent, but FWIW: I don't think you'll want 30-40mm on top. We had a long circular drive and parking areas all on slopes. I used 50mm plastic gravel grid trays. Finish material was 20mm black basalt that I shipped in in 16 ton loads. It worked best with the absolute minimum (ie just one stone where possible) above the trays - just enough so that the trays disappeared from sight. Any more and grip on the slopes was lost and the spinning wheels could break up the partitions in the trays beneath. But with minimal coverage, much less likely to slip (except the courier company delivery vans obviously as they have their max launch control permanently engaged). The basalt was ideal being very hard and grippy. Where we are now (while flat) has a light cotswold stone gravel that's really not suitable - over time (needs work annually) it crushes to powder. Don't know where your proposed riverbed gravel fits on the hardness spectrum.

You need different things for the different finishes. Ours - timber frame (MBC) will be part stone clad - off SurCav and part Wood clad. The whole thing needs to breath, but our stone mason is used to putting in what he calls fire socks to the Surcav bit. And we'll be using something like VFB 60/60 from Tenmat as cavity closures in the wood bits. I'm still worried about providing housing for a whole menagerie of critters so will be doing some more work on keeping them out, but MBC are only bothered about the need for ventilation and BC are only bothered about the fire risk so those elements are a must. Critter barriers it seems can be "model's own".

You've got your location set as "south west" which is a bit too vague for specifics. Most of us have knowledge of just our local office. Many are in deep doos. They have too few officers. Those there get over worked and leave making the situation worse. In East Devon it got so bad in 2025 there were literally none left - I've no idea what sort of service people there get. In South Somerset (where we are) they have a published schedule which suggests a decision within 8 weeks. That's just puff like the 4 hour wait in A&E. After 8 weeks I had great deal of trouble getting any info at all. Once I'd gone round the houses a bit and involved local councillors I found out that our assigned officer had gone on long term sick and everyone else was so busy her cases weren't being reallocated so we just faced an indefinite wait. After making a bit more fuss a decision was made 7 months after application. The snag is, such decisions these days come with numerous conditions, and to discharge the conditions you have to make an application which goes into the same queue. I'm happy to say that element is behind us now...but we bought our plot with extant outline planning permission at the end of 2023 and we will start the foundations on July 6th 2026. Its a daft system and process for a country that professes to want to build more homes.

Agree - take the hit on making good and just knock out a bit more plaster/wall - then you'll be able to carefully feed the cable back as you tease the old box out. If its just a 40mm move, there'll be a sizeable bit of filling around the new box anyway.

No Nick. The wayrock absolutely as standard. Then the blue polystyrene panels with pipe channels (+pipes) laid on top. Then the ply, ditra, and finshes. We put an oak "step" in the door thresholds to the en-suites but it was only 38mm and looked like we meant it more than it was a cover up.

The current project is an upside down house. As things have progressed we have gone Passive and won't now have UFH. However we too loved the UFH on our previous home under a stone floor (downstairs). At the start of the design for the current I wanted to replicate that stone floor - but upstairs this time as that's where we will be living. As such it is spec'd to have a Lewis Deck with 50mm screed (something like Kerracol) sat on top of the timber frame Chipboard finish. The UHF would have sat happily in there if we'd decided to have some. Last place we had oversize Ali rads upstairs except in the bathrooms where I stuck to wet UFH. Was a specialist "thin" polystyrene type of carrier with small diameter pipes - all from Wavin. Make up - 18mm chipboard (wayrock) on the joists, Wavin poly/pipes, 12mm Plywood, Ditra Matting, Ceramic Tiles. Worked very well for the decade or so we lived with it.

Got no personal experience, but was helping a friend research some of these and he was quite taken with the Mammotion Luba 3. There's loads of YouTubers posting about them. Seem to be pretty good at least short term - not been out long enough to know how they'll last.

I'd say it depends which way the windows face. I've had plenty of bathrooms with no windows at all and there has never been an issue with any of them (albeit all have had "extractor fans" not MVHR). Last place we had 4 bathrooms. One totally intrernal, which was fine. Other 3 with one fixed floor to ceiling window in each. Two of them absolutely fine, but the heat gain through the west facing window in the summer evenings was horrendous. I doubt just having it opening would have been the answer, I suspect an external louvre or similar was really required. If you live in the countyside as we do, its beautiful...but if you open your windows you do invite in a lot of lodgers (particularly after dark with the lights on) and not all of them are welcome. Opening windows other than in very controlled situations is greatly overrated in my view. Bring on the MVHR!

Interesting reading this thread. I always favour a hot water loop (called HRC I've learnt here!) which of course needs good insulation but eliminates that awful wait for the hot water to arrive. Where I differ is that I always insulate cold runs too and not just because of potential condensation. It depends what you want of course, but I like my cold to be cold not room temp. I also typically run the cold close to the hot and I want the minimum heat exchange possible between the two - nothing worse than tepid drinking water IMO.

Totally agree with having a hatch. Stuff happens. You (or someone for you) will need to get up there at some point. (eg maybe a repair or maybe vermin get into the roof void and spend the night scratching around). Cutting a hole in the ceiling later at some random position not knowing what's above is much wore than doing it to a proper plan. And if you never use it in your time...what's the cost been? A couple of hundred now vs potentially much more once everywhere is properly "finished ".

Our build is [will be?] in Crewkerne South Somerset and National Grid are the DNO and have a base there (took over the area from Western Power). I had a very helpful chap (Scott Bisset) discuss my requirements on site with me and suggest alternatives before handing on to the implemetation team (overseen by Matt Pougher) who have also been a pleasure to deal with. Seems to me you've just been incredibly unlucky with who has dealt with your application - a great shame for you. Can you "change your mind" and withdraw it all for a couple of weeks then re-apply and hope its passed to someone sensible?

Yes, this all sounds postively weird! I've recently had the National Grid out to our plot. We will be an infill between what are currently the last two properties on the line of the (overhead cable) run. The NG inspector suggested taking the supply from the last pole in my neighbours garden, but given the trolling we had through the planning stages I'm sure they wouldn't give us a cold let alone a wayleave. So the answer for us was to pay for a new pole (mid way between the last two on the run) and make our connection there. The pole has been "planted" and the connection is due next Tuesday. Didn't seem to be a problem for NG - from enquirey to installation much quicker than a water supply. Sounds like properly bad luck for you...I wish you well.

I suspect you'll get horrible gurgling in the bath and sink if there's no air admittance valve upstream of the basin. Otherwise generally "better" to drop into the main sewer from the top rather than end (cap the end for rodding) - but you may not have enough fall available for that at the moment, and what you have in mind will work.