Nickfromwales

I'd review the floor construction methodology, and do as a lot here have done, including what I do for my clients. Forget the screed, put the insulation down low on the ground, and then have a constructional, heated slab with steel mesh reinforcement for anti-cracking. The ufh pipes get cable-tied to the steel, and then the concrete pour is your finished interior floor ( less final coverings ). A small, cheap ASHP on this would be very cheap to run. Coming off oil will have its challenges also, as the oil boiler could never see just the UFH independently or it'll "poop the bed". At the minimum, you'd need to install something like a 150L - 200L buffer tank to accept the huge amount of heat the oil boiler will produce before it realises it's not even needed. If you run the UFH and radiators simultaneously, then you may JUST get away with it, but maybe not even then. Oil boilers like to light, burn at 100% ( or 0%, nothing in-between with oil btw ), and burn for as long as is possible, and this is because they do not modulate. This means that it would produced huge amounts of heat, the UFH would be taking 5-10% of that at most, and then the boiler would cycle on/off repeatedly ( referred to as "short-cycling" ) which would eventually ruin the boiler. A decent 5kW ASHP is around £2.5k FYI, or less if you go for a lesser-known brand. Rethink the floor, because, as stated, it shouldn't be heated with that poor a level of insulation, sorry! For your stated floor detail, you should be having rads on the walls instead.

400 is mandatory for bathrooms. Floors should have the same minimum standard. 600 o/c is crap for a floor, unless the joists are oversized.

The suppliers design with a too-fine element of bean-counting. I guarantee you that the floors / spans / deflection they allow when trying to win business is NOT what they'd specify for their own houses! Every job ( new build ) that I've worked in that had joists "to spec" @600mm were bouncy. One member on here had his done "to spec" and when he walked through the bedroom the fitted wardrobe doors moved / bumped into each other. Nope. Standard designs / calcs for these are carp, just like British Building Regs....."What's the crappiest thing we can churn out legally?"

🤣

Just send the invoice through, and I'll pass it on to management

IIRC the wool plus over-joist ( wall ) detail MBC quote is better performing than the beefier cellulose filled 300mm PH offering. Defo go wool inbetween and full sheets of rigid over joists, and then membrane / service battens / plasterboard. NEVER would I install floor posi's at 600mm o/c. Like a chuffing trampoline.

Yes boss.....

Can you copy this into the other thread? Most will know your back-story then, Capt. Randomthread!

Yup. And can be made to feel solid, and quiet.

With a non-recirculating extractor, every ounce of benefit the MVHR provided that day will be obliterated the second you put lunch on. Go see some "less crap" recirculating extractors before you base everything on one piece of junk

Assuming ICF or masonry / cavity build? What about your target airtightness score if considering MVHR?

Any lack of continuity, and "bye-bye" to the acoustic qualities Have you looked at hollow-core concrete planks as an alternative? The 1st floor will be inside the thermal envelope, so insulation is moot.

They keep all the best things for the English......even our bikes have square wheels.

Pea shingle is fine tbh, just throw the first sheet of EPS down carefully and use that as a walking board to lay the rest, eg without disturbing the rest of the levelled shingle. I'll be making up a straight edge and some perimeter timbers as a slide, to level this in minutes. If this isn't right, the whole thing is fecked so I'll be going to town getting the shingle level / flat etc. Maybe use gravel first, then just have a 50mm layer of pea shingle so levelling is a breeze. Bollocks to whacking / compacting layers of stone. It's a shed, and it'll be the best damn shed for miles! The beauty of a raft is that it doesn't need to be absolutely perfect underneath, unless it's taking a 2 or 3 storey 5 bed house that is. The steel in the concrete deals with any minimal depressions / voids that happen over the next few years from settlement. If I carry on designing this any more, they'll be holding my fecking wake in it!!

Have you committed to the MVHR? It sounds like it will be an expensive ornament, sorry!

Bonjour!

Hi. If you cannot attach to the oil heating system, which is 100% what you should be doing btw, then you may as well just install an in-screed direct electric heater wire and heat the slab up instead of a stupidly expensive SA / Thermino as the slab will have inherent storage and release characteristics already. Before we advise any further, we would need to know how much insulation and how thick the slab / screed will be, please? You'll get probably less than 3 hrs of space heating from the largest SA unit, the 12-14kWh one, when fully charged, if you're lucky. Every one of these I fitted for space heating, with plans and designs approved directly by SA, ended in very expensive arguments / tears. The ones that didn't blow up, that is

Floors down first, every day of the week. Makes for a much nicer look to the cuts around the room, and also allows you to seal the floor tile to the wall around shower / bath / splash zones. Plywood, glued and screwed onto that floor will be easy, cheap and simple to do ( with minimal additional build-up / height at the threshold ), and defo screw the floorboards down tight first, as if you start with a loose floor, that's what you'll finish with ;). I've never, not once in 30 years, laid a cement board down when tiling a regular floor, like this one is. Way too overcomplicated AFAIC. For sound deadening, the floorboards, plywood, adhesive and tiles will get you where you need to be. If you're super fussy, pull up the floorboards and fill the voids with acoustic wool. Then when you re-lay the floor you can mark off services etc and screw the FB's back down with extra gusto! If going for an UTH mat / wire, defo use insulated tile backer boards ( Wedi / Marmox etc ) as the response time and wasted electricity would otherwise be a bit of a PITA ( but not the end of the world ). It's 1st floor at the end of the day, so the UTH would be strictly a comfort installation, but on a concrete GF room it would be almost obligatory these days.

As long as it’s like for like I don’t think it’s notifiable. It’s not a change of purpose. Ventilation, and air admittance on the SVP will be the hot topics, and insulation on the external walls. If lighting / electrics etc is all new that’s going to be notifiable.

It will, just, if it’s within 2m. It’ll be well north of 15m2 that’s for sure! 8.8m x 3.3m internally to just cheat the 30m2 rule most prob. That’s the one rule I will observe to the nth degree! I think for most other misdemeanours you can beg forgiveness retrospectively.

I wonder how long a Fray Bentos would take? 6 or 7 batteries lol. All day breakfast in one tin. BOOM!!

Meals on wheels!! 👊

😲 I don't know what type of girls you date mate, but that would give even a hippo a limp!!!

I'm working on not actively pissing the neighbours off with a monstrous build, but after that I'm just going to fill the space up and worry about a retrospective PP app if I have to. More fuel for digging out an extra 200mm or so of spoil and dropping the building / ridge height as much as possible. Life's best when everyone is playing nicely together at the end of the day . I'm happy with 2.1m minimum internal head height and a reasonable pitch apex roof ( solar E/W split ) and hopefully nobody will give a toss.

Tell me about it. I have one. Luckily for me they've clearly used up more than their 50% in PD, so I doubt very much they'd be causing me any grief.