Redbeard

You *may* get away with using an extension tube (flexible brewer's/wine-maker' tube is what I have used. I say *may* because the extra length slows the flow and if the first 'hit' is not fast enough nothing sticks and you just end up with a foam floor. It has worked for me, and also it hasn't...

Glad to have been of help. OK, so you have maybe decided to go for the +125mm on the roof (subj to Planning approval). But before you do that... Can you add a dimension for floor to horizontal ceiling (I could draw it and measure it but (a) I am lazy and (b) I have lost my scale rule!). If it would not make things too crazy tight I have in mind a proposal to Bldg Control. For the width of the doorway 50mm PIR between rafters (leaves a 25mm vent gap which I regard as sub-optimal but as you are re-roofing with slate, get a really good membrane and you should be OK for that small area). That gives you a 'tunnel' to enter the room and you don't crack your head. For the rest, 25mm PIR between rafters and 75 below, fixed at wide centres with insulation collars/screws and tightly taped as VCL. Plasterboard fixed directly below (which required you to remember where the rafters are under 75 PIR. For a loss of a further 25mm space, x25 x 50 battens at right angles to rafters over the PIR and adjust centres to suit your chosen boards (I can no longer wrangle 1200 x 2400 so I use 900 x 1800. A very rough calc (unadjusted for the bridging of the rafters) for the main area with the 25 + 75 'sandwich' gives a U value of around 0.22W/m2K. You could propose that to BC as a compromise and quote the section from the Regs in my previous post. Note that even that reduced amount would give you about 9-10 times the insulation value of the un-insulated roof. They *could* ask you to have a SAP calc done to prove that doing it to the full std would have a payback of more than 15 yrs but I have only been required to do that once. Edit: If you decide to go for the 'raise the roof' option be very clear on the design of the box gutter and the box it sits in. I would (could) be concerned about condensation on the bottom and sides of the metal box , wetting the timber box. Maybe consider building the 'under-box' out of Compacfoam or XPS? I would also get a roofer to express an opinion of the 'tails' on the box gutter. I would worry they are potentially too short/not profiled sufficiently.

Do the training and become a registered installer. You don't actually have to work as one, just be on the list. I found myself a registered installer for a couple of companies mainly by dint of buying their stuff. Fills you with confidence, doesn't it?!

@Neverfinished, could you please post the dwg again with dimensions, so we can see what the pinch-points are? I am particularly unsure of how the 1.72m headroom 'kicks in'. Is it because the stair comes up under the sloping roof? Is there so much more headroom in the room itself that you could fit insulation under the rafters? Your statement below suggests not:

What is the plan for insulation in that rear monopitch roof? If, for example, you are trying to use something 'friendly' (and perhaps to achieve a'better than Regs U value) whether below rafters as a cold roof or above them as a warm one, you may find yourself 'fighting' with either the GF windows on the inside or the FF windows if the insulation is above the rafters.

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.

You need a structural eng'r too, else your Bldg Regs application will get stuck when they ask for proof.

Get them made to your Structural Engineer's own design. Yes, not every steel fabricator will do stainless, but some will.

1. Could well be, depending on whether you are expecting them to do just dwgs, or dwgs & spec, or dwgs, spec and site supervision. Check they are fully experienced for the 'package' you want. 2. Maybe. I effectively 'drew' mine, but gave them to someone to 'computerise'. Sub out the SAP, again, preferably to someone who knows the building physics as well as how to drive the software. 3. Absolutely no idea! Sorry.

It's a very non-scientific 'diagnosis' but if you look at the shape of the left-hand-side of the empty footing trench the crack seems roughly to follow that shape, suggesting that the crack is between the existing (pre-extension) ground and the (presumably softer, less compacted) fill.

Given that it appears to be smeared with sand/cement could this perhaps be a (modern) fibre cement verge trim? I used one 2 years ago. If you think it could be a heck of a lot older (say no later than 2000) there's a possibility it could contain asbestos. When you say do you mean had the whole roof re-laid? If so, unless someone had some very, very old stock, I think you can be pretty sure it is not asbestos-bearing. If in any doubt whatsoever get a sample tested.