Nickfromwales

+1, just don't go mad with the wacker!

Yup, they will not thank you for this unless it has been agreed comprehensively before they arrive on site so they can adjust their time / labour fairly.

The man has spoken, and his words are wise ones. "Heed" y'all!! Airtightness is the money shot here for sure, but if possible also put some 10mm (or thicker) Marmox / similar insulation board between the flooring and the joists to kill the repeat thermal bridging, if you can lose that slight gain in floor height?

Have the council said you can have a white line painted across the dropped section to prevent cars parking there? Kind of moving the problem sideways as they'll just park it right back there after the crossover is done. Last resort; Ask a kind Pikey to 'collect' it......

Finish the patio 200mm from the up-stand wall at the turfed area and fill it with 3/4 decorative chippings. I think this will need to be around 300mm deep to be effective as a mini soak away, meaning you’d need deeper foundation for the wall. You defo don’t have any storm or foul drain at the rear?

It’s never one pump. That’s the issue. You’ll need at least 2 pumps and to be routinely testing, cleaning, maintaining them for the rest of your days. The time you relax and think “I’ll get to it next week” is when the building will be flood damaged. Two words spring to mind, the second is “that”. You can install panels as low as 8° so I still think there’s potential to be at ground level with your sole plate. If you are staying on this path then the above is the best advice; never rely on one pump as it will fail when you don’t want it to. Also, you need to allow for a system that will be able to cope with a 1-in-a-hundred-year storm to be anywhere near even close to considering this solution. You’ll need a sump about 600mm in diameter, with a closure plate to stop an infant / human falling in, and that will need to have the two pumps dangling on stainless chains so they can be lifted out to be checked / inspected / replaced. What a massive pita though. Just put the solar due south, get the shed out of the ground, and keep it cheap and simple. The cost of all this craziness will mean your PV payback (RoI) will be multiples of decades so just completely dumb maths afaic. You’ll have zero benefit from it too, as the electricity to run the pumps all wet season will consume all that you generate each summer, and more. Factor in replacing the pump(s) and you’re wasting time, effort and at an expense that you absolutely will not recover in your whole lifetime. “Nuts idea”, sorry! 🫤 Ill get my tin hat ready

It’s OK Mike, I’ll edit it lol 🫡 🙄😉

FYI, my 6m x 4m man-shed / office has a sloping flat roof to comply. It begins with an internal head height of 2.1m, at the office where I'm sat, and then rises away to the doorway end. Zero of this is below ground, other than the base. Plenty of room, and acknowledges the PD requirement for max height etc

Ok, so why such a "tall" building? Is this destined to have an apex roof? Why not go for a flat roof and avoid the height. I don't have any other suggestion other than "don't continue with this plan, and work a new plan to have this above ground at soleplate level, doing away with a pumped drainage. There are so many red flags here i am losing count! Please give us the whole story so we can get you the best replies.

14 - timber lining? I wouldn't want wood there! Why isn't that cement board also?

This is the correct route, but then you must NOT use the paint as the layers will need to breathe. FYI, putting the AT paint on the floor will be utterly useless and do diddly squat for AT. The AT needs to come past this layer in the garage, and then that membrane gets taped to that layer. Look at AT as a perfect cube, will all lines, corners etc in contact with one another, as anything less will gives terrible results for a lot of time and money spent. If you can have the cylinder anywhere else, then do so, the garage should be the absolute last option as the heat loss over winter will be significant (albeit a cost / compromise that you may be willing to accept to gain space inside the house). Go way above B Regs levels of insulation in the ceiling of the garage, as this will pay huge dividends over time, that's because the garage will be the coldest draughtiest area in the building so will attract heat loss. You may also need an airtight door separating the garage from the house, or do away with that altogether, IF you want to get a great AT score? You buy insulation once, it lasts a lifetime, but gas and electricity will keep costing you for your lifetime, a cost you need to mitigate against with every effort. The same can be said about the insulation everywhere else, as UK B Regs offers the poorest house you can legally build, and is an utterly dire standard on a very, very good day (and that is the most you can expect if / when the work is executed meticulously by a builder with a conscience which doesn't happen with high frequency btw).

Well, they celebrated building their 100th home in the UK in 2023, but that is a tiny percentage. My marketing team discovered that there are somewhere between 15,000 to 18,000 UK self builds per annum in the UK (domestic 1-offs) as an 'average' (albeit these were quite difficult statistics to accurately ascertain) so that's the way I gauge their 'presence'. Might I ask what the attraction to this particular company is? I am indifferent btw, just more curious than anything. What size home are you building?

Which just goes to show how under-qualified these bodies are to provide a global summary of an entire property vs just adding the number of ticks in particular boxes and then down-grading you like Neanderthals.

Are you gluttons for punishment? Why on earth (or clay lol) are you going down so low with an outbuilding??? Is this to get the ridge height down to appease permitted development or planning rues? Sounds like you are making ridiculously expensive and unnecessary rods for your backs here, sorry. Having a garden room that needs a sump pump is insane (and my ICF guy is Canadian so I know they do these types of things without batting an eyelid) so I think you need to have a serious sense-check here before going any further.

So when exactly did they put this through your door?

The issue is about zone control then, as the flow temp may be "OK". How do you propose to control the heat input and floor temp? Do you have UFH anywhere else in the dwelling?

Most ASHP's have a 7 year warranty, from the few I've been associated with, and that's even from the likes of Stiebel Eltron who offer 5 iirc. Lifespan / longevity is found (promoted) by good design and sizing the unit so that it can live a relaxed and long(er) life.

You may be 'over-worrying' here tbh. Permeability isn't the issue here, it is movement. If you allow 2mm per day you'll be A OK, and if this is primed properly and a good, conscientious tiler employed vs 'the builders mate', then you have no reason why this shouldn't be a successful undertaking. Excellent prep work can be wasted on a shite tiler and I've seen them all. FYI, I've been tiling high-end projects for 25+ years. FWIW, I would have given you a bollocking for removing the battens, as that will likely do more harm than good. The battens will offer some fixed mechanical bonding, to both the screed and the Ditra + adhesive, and will likely be the backbone so they defo need to stay.

Bum steer, sorry. Do NOT fit steel plates, you just prime the battens and fill up with tile adhesive for the Ditra to bed into. I'd recommend something like (a little more expensive but very good) Bal Flex One tile adhesive, LINK, as this offers even further decoupling by itself.

Hi. Are you improving and upgrading the existing bits to match the performance of the new SIPS stuff from Potton? I assume they've comprehensively commented on this already? That assumed, MVHR will be mandated and then a full heat loss (and overheat) analysis can be done on desktop to allow you to tender to any decent A/C company. Best to get the horse and the cart in check, and then you can provide vital information to these 3rd parties YOURSELF, vs expecting them to do this heavy lifting. The best due diligence is the one(s) you do yourself. Potton should have already given you ACH targets and U-values etc for their 'bits'? Just need to add the existing part and you're off to the races. You could have elaborated here just a little bit lol...... No, it wont. Unless these are 2 separate and non cojoined items then they will always be as one; they'll be the same heated and airtight envelope, so the weak one will bring down the stronger and not vice versa. Who's advising you on your M&E side, as this sounds like you're getting less than great information upon which to be making these decisions?

Yup, what he said 👆

Yup. @HandyAndy, you cannot connect to the underground pipe with that boss strap. Completely against b regs. You need to expose more, get a 110mm Y branch (not a T branch) and then extend a new piece of 110mm pipe to a gulley pot underneath where the shower pipe exits the wall (as close as you can get it). You need to approach your building control person BEFORE going any further.

I’d say you should look for min 16a or a comfortable 20a continuous load device, 13a is still cutting it a bit fine imho. Shelly’s can do this and seem well suited to this application. It’ll need a separate 16a or 20a supply for each ‘channel’ / immersion, so don’t take both feeds off one breaker (so you’ll need 2 positions in the CU to do this properly too).

13a peak, 10a constant. Resistive heating can suck full power for sustained periods, and everything warms up really quickly. Fuses will run ‘molten’ where the metal is borderline melting point, and the heat then spreads and it goes terminal. Use a timer to fire a pair of contactors, and make sure the 2 immersions are fed independently, and things will be less ‘toasted’ looking

Contactor all day long matey. The plug is rated 10a continuous…… you dodged a bullet there 🙁