Redbeard

I realise complexity makes £/m2 costs a bit meaningless, but my GBS (21 Degrees) 3G wins came out at about £735/m2 supply only in 2022/23. (Tried to send you a PM re another firm but apparently you cannot receive messages...)

I fear wood-fibre etc. *will* 'break the bank', at least compared to the costs of PIR. Don't get me wrong, it is exactly what I propose to use in the refurb of my rooms-in-the-roof, but mine is a steep-pitched roof with plenty of headroom. My 'sandwich' is proposed to be: 20mm rigid WF (lambda 0.044W/mK) between 75mm rafters leaving the recommended 50mm (well, 55 here, but Gov't guidance says 50) ventilation path. 225mm flexi WF (lambda 0.039W/mK) in Larsen Trusses, and 20mm WF again as plaster carrier. This sounds like it would take a lot of space which you have not got, and it *will* cost plenty. For me this is the right thing to do and I will shut my eyes and scrimp on other things to achieve it. Unless you use PIR (and I am certainly not trying to persuade you to) even your +5" on top will not get you a compliant U value. There are some get-out clauses in the Regs. See pp 25 and 26 of 'Part L': https://assets.publishing.service.gov.uk/media/662a2e3e55e1582b6ca7e592/Approved_Document_L__Conservation_of_fuel_and_power__Volume_1_Dwellings__2021_edition_incorporating_2023_amendments.pdf And try to get a word with a Building Control officer. Depending on staffing levels they can be hard to pin down, but as well as ensuring compliance with the regs they also have to be realists. I think if you are trying to get an area-weighted U value of 0.15 with such limited space in or under the rafters you might find that you are trying to get more insulation in the eaves voids than they will physically contain! Fairly certain Planning permission would be required to lift the roof but, importantly, if you are using WF or similar, 5" will not be enough - see my lay-up referred to above. Also, as Warm roofs are typically done with rigid material, the weight of rigid WF @ 140-180kg/m3 would, I think, break your roof! Flexi is, I think, about 55kg/m3. I am running out of stamina tonight but have a look at this and fire back further Q's and I'll try to help if I can.

When you say 'running out' I take it you mean running downhill to the dormer cheek. Am I right? I can see that )possibly) on the 1st pic (RHS) but not sure if I can see it on LHS, or whether I am just convincing myself I can! I am generally fairly pernickety, and I would not, I think, have picked up on that. How often will you stand and look at it? If it will annoy you forever, change it. If you can programme your eyes and brain to 'ignore', live with it. Ah, I have just read again and seen: Hmm, maybe my advice above won't help then. I *suppose* you could basically eye it up, decide on what would look right to you, decide the adjustment required for the eaves course, alter the battens accordingly and go from there. I cannot think of a more 'scientific' way. If that helps a little, good. If it doesn't, sorry.

If you are really 'taking off the roof' why not try to get a structural design which includes removing that cross-timber and providing alternative strengthening? Have you got a structural engineer? Have you been through Building Control? Is Planning Permission required?

BC won't like it, nor will they like the fact that you are not using permeable paving, I think. Are you getting Planning Permission? Has the would-be contractor done a percolation test? If a soakaway does not soakaway it's just called a. And it can also soak away too fast. That's not good (or allowed, I think)

What for? Footings, lintels etc. @Tony L, did you not need a structural engineer? A long time ago the architects I worked with did their own SE, but from quite a long while ago they started using consultant SEs.

AFAIK this is now out of date. (Yeah; checked it!): "28 Feb 2023 — England and Wales both introduced new building regulations that tightened the limiting air permeability for new buildings from 10 m3/hr.m2 to 8 m3/hr.m2". (www.partel.co.uk) I am pretty sure it is 8m3/m2/hr (@50 pa) now. (p.a. is per annum and should not be there!!)

I am not sure it would (though there is probably not a requirement for scaffolding to be metal -I have no idea). However occasionally you'll see a scaff self-erected by a (building, not scaffold) contractor which looks, frankly, frightening.

Well... the louvred covers with loose flaps gives some back-draught protection but if the wind is in the wrong direction they flap and chatter like nobody's business. I swapped them for cowls with a 100mm flap which, being 'sheltered from the wind', does not 'chatter'.

I have one of these. Pretty enough but there's no back-draught prevention.

Have you tried Ecology?

Really? I realise that's glazing only but even that seems low if it's a 28mm unit. Is it, or have they used a smaller bead to give you a bigger rebate? (I know you can do that with Rehau 'double glazing' frames, up to as wide as 44mm - although someone from GBF who has done so said the tiny bead is a real bu**er to get in and out).

+1 to that.

Excellent. Sounds like 2 hops forward!

OK, it's a long way away but depending on the distance between where you'd connect and the main sewer I wonder if your water authority would accept the ditch as, in affect, a linear 'leach-field' (attenuation 'device')? Suppose it depends a lot on whether the clay persists at the same level for the entire run of the ditch.