Redbeard

I guess the difference (and the issue) here is that the OP does not know how much insulation is above the roof. If there's 'not much' then following the rule of thumb OP could only put 50% of 'not much' below the deck in any case (or schedule re-insulation for when the warm roof cover needs attention).

Yes, there is a rule of thumb (2/3 vs 1/3), but note that it relates to R value, but thickness.

Exactly that one! Although my 'filing system' means that I have mislaid the one which I'd need for floorboard nails!!

Is the joint between boards 1 and 2 at all open? Could you run a circ saw down to cut the tongue? Even if not, if you punch the nails down into the joist with a parallel-sided punch you should be able to wrangle it enough with the existing (lack of) 'weasel room'. Even if you cannot get the nails right through the bottom of the board, 75% of the way should loosen everything off enough. I once did a floor of approx 32m2 like this. We allowed for 20% wastage, and ended up only replacing about 4 linear metres of board.

Has it got to comply with bldg Regs insofar as it may contain heating equipment? 4 x 2s are beefier than the 3 x 2 used in many Victorian roofs, so in terms of 'will they do the job?', probably yes (though we don't know the pitch, so don't know if it will need a purlin). 'Will it comply with Bldg Regs?': No idea!

In any case, @ectoplasmosis, if your are comfortable with using the Lime Green I see no reason in principle (I have not read their blurb) why you should not use the LG product for the parge coat.

OK, pictures follow later, if only to prove that I am one of the world's worst photographers!! I checked the data sheets for 'Solo one coat' and see that, as I was sure must be the case, they do require mesh: Common Uses Woodfibre Insulation Boards: simply skim on Solo in 2 passes with mesh in between, around 10 mm thick. So effectively they are suggesting the same as I do, which is that you 'split' the base-coat with mesh. As I described it layers 1 and 2 of plaster are in effect 2 halves of the same coat. The difference is that (a) they don't suggest another coat of base-coat (arguably not necessary unless you get mesh 'ghosting' through) and therefore (b) that you have to trowel up this 'split coat' as your top-coat.

Don't squash the insulation. Leave a ventilation gap between it and the boards. I lifted a board of a beautifully-constructed storage platform during a survey and water dripped off the underside. Yes, that loft had other undiagnosed (till then) ventilation issues, but best practice usually involves a gap between insulation and storage platform.

Remember to 'cloak' the thermal bridge where externally-insulated walls meet internally-insulated walls. Draw an imaginary diagonal line at the end of the IWI/EWI 'junction' and you can find a path which misses both sets of insulation. Carry the IWI round a small distance (about the length of a piece of string) in such a way as it does not look stupid onto the wall which has IWI. The more you can lengthen the 'brick-to-brick path' the less critical is your thermal bridge (heat-leakage).

Do a 'parge-coat' (air-tightness layer) of lime plaster over the bricks first. Minimum 6mm thick, ideally. If you can, take up floorboards so that you can extend the parge coat down to the ceiling of the room below, for 'picking up' later when you do the rooms downstairs - however much later that may be. Leave to dry. 'Butter' the back of the boards with lime plaster as an 'adhesive' using a 6mm or 10mm toothed trowel (6mm if you vcan hold the trowel at 90 degrees to the wall - not the natural way - or 10mm if you tend to hold at a shallow angle, as you will be 'closing down' the furrows to 6mm or less anyway) and apply the boards, being careful to ensure that no plaster gets 'picked up' in the joints - plaster is not as good an insulator as WF! Then apply lime plaster as recommended, with mesh reinforcement. I have never used Lime Green products, and certainly never plastered WF in 1 coat. Not to say it would not work, but the way I was taught, for the room-side, not for the adhesive layer (with Baumit products) was: - Toothed trowel coat - Glass-fibre mesh laid gently onto toothed coat. Allow to stiffen very slightly - 'Wet-on-wet' coat of plaster to 'hide' the mesh as much as you can (IME you won't hide it completely) - When 'dry' (1 day minimum) a further coat to hide any residual 'ghosting' of the mesh. - Allow 4 days to dry (you may get away with 2 in really warm weather before coating with (in my case) Kalkin Glatt, a very thin finish plaster, which neither 'builds' much, nor hides much, so get the previous coat of base-coat nice and smooth. This is not an advert for a particular product! I just find this brand easy to use and have seen no reason to chance in 9 years. Would some pictures help?

Hmmm... You should not really need to wait, unless the fan is really much too small. It really wants to be sealed into the opening. I worry about the cat...

Can't see v well, but is the dropped floor where the hearthstone was?

Yes, I was not suggesting the Morrie at least could be put on the road, but there may well be re-usable bits 'hiding'. I did once have permission to put a motorcycle in the living-room, but it never happened. Worked on bikes in a few kitchens, though! When you have removed the under- (over-) growth show us pics of the other cars and I bet we can help. Any motorcycles....? 🙂

How chunky are the kitchen joists. Are they more spindly - just to take a ceiling - or do they look similar to the ones above. If the latter, why not strut between the 2, so the kitchen joists take some of the load?

Hey hey! That looks fun! Agree the journals etc must be of interest to someone. With the mixer and dumper you may well find that the engines, being so basic, are 'resuscitatable' (if that's a word!). Don't assume that the Morrie has only scrap metal value. Dig deeper. Perhaps it's the camera angle but, although the shape looks 'Minor' the bonnet looks longer than a Minor. Grille looks Minor, though. Looks like a door is open, so internals may not have been 'saved' much. The web tells me that there is a thriving owners club if it is a Minor: https://www.mmoc.org.uk/. I bet an invitation to members to come and look on a given day and make an offer would be well responded to. What are you going to build when it's all clear? (Or is that already on another thread?)

@joe90, I agree in principle, but @Dee has already put said notches in the wrong bit, a remedy for which you have suggested. @Dee asked "So, in what scenario would you notch the top of a joist? Surely you wouldn't run waste pipes over joists?" No, I would not seek to notch for that big a pipe, but @Mattg4321 's suggestion was, I think, that it could be less critical at the top (although still requiring strengthening). I agree re holes in the middle, but I am not sure what max dia hole (at joist ctre) is allowable in what jst depth. Edit: Now I am! I re-read that Eden DC link: 0.25 xx jst depth, so 37.5mm. O.P. What's the waste pipe dia?

Have I misunderstood? Why not?

I had previously written: "Sounds like a potential recipe for interstitial condensation, whatever the Glaser Method (BS condensation risk analysis tool) says. Glaser method will only spit out results according to the gist of what you tell it. If you say it's got a VCL it will assume *perfect* VCL. I'd get it modelled at least, if you have not already done so, preferably in a dynamic model such as WUFI, but practitioners are hard to come by, in my experience. The Glaser method, if I remember rightly, covers itself in saying that the outside of the 'sandwich' should be permeable in case water vapour *does* get through. Your tanking slurry would/could mean that the wall is no longer permeable." The 'right place in the sandwich' would be on the warm side of the insulation. Theoretically the foil on the PIR (the 'room side' of the 125 layer) should be the VCL, but it needs detailing *really* tightly, and I would suggest using air-tightness tape on joints and perimeters, not foil tape which, at the corners, is not strong under tension.. Normally you'd go for VCL immediately next to the plasterboard, but at that point your VCL is incomplete because you have battens. You could use a separate VCL in this position. Is it possible to send us a picture or diagram of how this will look? How sheltered is it? How likely is wind-blown rain, etc.?

Why are you paying for heat when you effectively have a hole in the top of the house? Would it not wait till you have the insulation in, then a given temp rise costs you much less... No idea why font is pale and tiny.

HSE had a really good guide to working with relatively low-risk asbestos materials. For soffit boards they suggested shaving foam. If you used that (although you should still wear a mask and all the required PPE, of course) the dust released would be minimal. Dispose of the shaving foam and 'dust' as you would any asbestos. https://www.hse.gov.uk/pubns/guidance/a9.pdf

Bet the glulam moved less than the oak would have!

...and if you want to go for 'woody', I find it a bit hard to see how SIPs (with some inherent thermal bridging AIUI) is much better than a TF and fill of your choice. Do you mean you would DIY if you did SIPs? You could also DIY a TF. I did my 'design', got SE to 'prove' it and off we went.

Joist depth Notch depth 150mm 18mm 175mm 21mm 200mm 25mm 225mm 28mm 1 more row • 5 Oct 2022 Notches and holes - Eden District Council

Still bothered about the tanking. It seems to be an impermeable barrier at the very wrong point in the thermal 'sandwich'.

Yes, @joe90 exactly what I meant. That way you can get the joints good and full, even if you can't get in to 'tickle up' the pointing. If it is so close, and thus so sheltered, I should have thought just striking them off flush would suffice.