Redbeard

Do an 'invisible mend' on the soakaway position.

I ordered a whole load of C24, and when the delivery came some was C16. Took that part of the order back to the yard and out comes the bloke with an ink-pad and a stamp... Oh look! C24! The official explanation was that all their timber could be graded C24 but if they stamped it all thus some people would think they were paying over the odds, when all they wanted was C16. So they stamp some of it C16 and some C24. It must be true.

Can anyone recommend a supplier for 125(W) x 100 deep black alu ogee guttering, fittings and fall-pipe? Did a search and am now too overwhelmed to buy anything! Thanks

No, absolutely not fine! But depressingly common. I have had a contractor tell me the same thing, but being told it is fine does not make the insulation value any better. If the 2nd (under-side) layer is not completely tight to the first (between-rafter) layer, and the ventilation is working as it should, then you may even get thermal by-pass - cold ventilation air getting between the layers of the sandwich and effectively negating the effect of the between-rafter layer.

Yes, water-resistant plasterboard exists, as do cement fibre boards for shower panels etc, but loads of people have (maybe shouldn't have, but have) tiled onto bog-std plasterboard in the past with few or no issues. If the grout and all the perimeter joints are good then where does the water get in? I'd stop worrying for now, grout it well and re-do any mastic as required. Stick a note in your diary for an annual check and re-tweak as required.

What about costs of insulating the existing walls? Part L of the Building Regs will apply to all the elements of a conversion.

Looks a bit *too* black to me, but here in S Yorks (and I am sure other areas too) we have 'Black mortar'. The (lime) mortar was made using an aggregate of mixed sand and steelworks or colliery slag. It's awful stuff to hack out, as it was also used in basecoat lime plaster. I think as a theory that does not stand up, though, as if I understand you correctly the render was over the lot, and from what little I can see the render looks like sand/cement and thus probably much more modern than to date from the 1920s/30s heyday of 'black mortar'. Oh well, it was worth a thought!

@Chris HB, see www.heraklith.com , for example.

Wood-wool and lime? Using it on my extension as I want to avoid plasterboard and gypsum. Heavy, and not cheap.

Hello, You say 'Hampshire, Suffolk, Wiltshire'. You also say you need to be near specialists etc. Should 'Suffolk' read 'Surrey' or do you just have 2 disparate search areas?

Welcome! There's a wealth of experience on here so I am sure you'll find what you need. If it's general (eco) retrofit perhaps also have a look at https://sdfoundation.org.uk/wp-content/uploads/2018/01/2015_bristolsolidwallinsulationguidance.pdf and (Scottish) SEDA Sustainable Renovation guidance: Chris Morgan, John Gilbert Architects: https://static1.squarespace.com/static/5978a800bf629a80c569eef0/t/5beca5f021c67c2280e66de3/1542235691571/Guide+to+Domestic+Retrofit.pdf Also look up the Gov't's Best Practice guidance for under-floor insulation, internal insulation of solid walls, room-in-roof insulation and one other (I think) that escapes my fevered brain just now.

Hi @francis0990, I don't think there's any substitute for structural engineering advice, whether from an independent SE or from the timber frame co.'s SE. As @markc states the doubling suggests load-bearing, and it is not worth taking risks.

Some installers will say a 'thin solution' ('insulated mat' - type pipe trays) is OK. I am very convinced it is not. You don't want to be heating a void or a slab. A client had 75mm PIR below UFH and I still do not think this is sufficient. I would like to see 150mm. (BTW, it does not have to be PIR - other choices - including natural materials such as wood fibre or cork - exist).

You say "the most i feel I can sacrifice in height is 5mm including wood floor." but then you go on to say "What would be the best to put as underlay? 25mm eps topped with backer board". 25mm + backer board is a lot more than 5mm! Was the '5mm' figure meant to be '50mm'? If the latter then a vestigial flooating floor of 25 PIR, DPM as VCL, 18mm T & G OSB + finished floor may 'cut the mustard'. Not goood enough for UFH, though, IMO. Remember, though, if you lift the ground floor by c50mm you put your stairs out of compliance with Bldg Regs, unless you can make the bottom stair a 'landing', in which case, IIRC, it can have a lesser riser.

The problem with using a long extension tube is that it slows the flow very significantly, so the tendency (on full pressure) to blow in and 'stick' is lost, and you get a lot of falling back out. Could you not open out more on the outside, weasel a bit of board over the hole on the inside, then fill back towards the outside before finishing with brick or whatever the external skin is? As far as the drain connection goes I wonder (if you could let off the bracket on the horizontal run) whether you could get a 110mm stop-end, drill a hole in it and shorten the 'pipe end' so that you can slot it up onto the 40mm waste, then down into the rubber of the socket end. Then a finger-full of silicone to seal, if you feel the need to seal.

I doubt there is a difference between a hole in the sash and a hole in the top rail, but the top rail appears to have mmore 'meat' - unless there is a bigger 'downstand' on the outside). Why would you want to fit a trickle vent into a tight space on the sash instaed of a more generous space on the top rail of the main frame? @HughF asks an understandable Q, but one answer could be 'as part of a thought-out decentralised mechanical extract (dMEV) system' (if MVHR is beyond the pale).

Don't know what the claimed U value is, but my rough 'n' dirty calc (assuming 2 skins of brick, where yours will be 1 x brick and 1 x block) doesn't even get the Bldg Regs (England) U value of 0.18. It might if you substitute lightweight block (and maybe, as often happens, if you assume that the air gap has still air in it - which it almost certainly won't!) but it'll be a close thing. Also the 'spec' is incomplete. 50 PIR inside the block skin is fine, but what is it finished in? If it's insulation-backed plasterboard then (a) it is 50 + 12.5mm and (b) the VCL will only be perfect on the back of the boards. The joints won't have one. If worried re loads on the wall you could do 50 PIR, taped tightly at all joints and perimeters, or add a plastic VCL treated similarly, screw 25mm ply to the wall and then plasterboard (or even Fermacell if you don't dislike cutting it as much as I do). It's a faff, though. If it were me I'd consider getting the cavities built empty (and I'd be tempted to go 150 - 100 is not too exciting - and carefully (no rubble and cr*p inside) then get the cavities fully filled with graphite EPS beads when you get your old cavities filled.

Welcome! You don't mention insulation, but I guess it is 'fairly original' but with 'non-original' roof insulation and the addition of cavity wall insulation. What's the insulation spec?

I confess I did not always dampen down, , and I never had the 'expansion failure' that you have had. Have you asked SF to investigate? I am sure they will refund, but it wants more than that, I think.

Used mountains of No Nonsense foam and never had an issue like this. A few stuck valves, yes... I have now moved onto (much more expensive) Illbruck FM330* and would not use anything else (unless I want adhesive grade, of course). (*Satisfied customer - not salesman!)

"It is almost completely air tight but at the small points where it is not...." Errrr....... Good luck with the 'negotiations'. Of course they may not entertain comparison with others' products but what your pics show is not typical.

Yes, that's not right. The fact that you have condensation on some of the frame and not on the rest suggests a local shortcoming. As far as the condensation on the glazing goes I don't know the glazing spec but my triple-glazed (3G) windows (some 4/18/4/18/4/soft-coat Low E/Argon and some same spec but 16mm and 20mm spacers respectively) have *never* had any internal condensation*. What's the make-up of the Velux 3G unit? * Loads (frozen) on the outside!!

200 PIR will give you 0.11 at worst. What is your target U value and how much extra will the M-F give you? If the timber counter-batten is 25mm I would wonder about loading it up with the wight of the 'sandwich'. Are you going to use stainless screws to reduce thermal bridging? Even if the battens are only 25mm how much will x number of minimum 250mm S/S screws cost?

I wonder if the ridge section is the width of a 'landscape' panel, in which case I guess you'd get 5 panels up to the L of the stack. One more can go anywhere you want in the remaining triangle. I think 9 might look 'busy'. I am no expert of aesthetics, and not a lot bothers me, but I think the 'notchy' look where PV 'climbs a hip' is not to everyone's taste. Prices look about what I'd expect. Some have, I think, had 4kW for £4k or just under, but £4400 sounds acceptable to me (especially when that could have cost £17 - 20k in 2009/10!!

"...So I’m not looking to fit solar panels " Presumably not = 'now'.