Annker

@Iceverge Yes certification isn't a concern in any event as the project is a renovation. And yes, I had been wondering if air tight tapes were essentially strips of air tight membrane, certainly a cost saving to be had if they are.

Ah interesting you suggest Passive purple. I follow the Intelligent Membranes youtube channel and they have been posting up a lot of videos over the past few days showcasing PP. I have those video saved to watch later but I think it will be a product I will be using if not in this instance certainly somewhere in the house. @Iceverge I believe you had suggested sealing around joist ends in a similar manner when you were critiquing my IWI build-up, so a bucket of Passive Purple would certainly get used on the project.

Its a suspended timber floor inaccessible below. The build-up is similar to a warm roof build-up. (X-section below) The plan was to run a tape or strip of membrane say 3" along the plywood floor and 3" up the wall sealing any air coming up the perimeter of this room.

Surely the Pro clima tape is certified for air tightness, AFAIK thats is their specific sector. The Illbruck and adhesive definitely is not a certified, its just a combination that I've had good success weatherproofing with, and rightly or wrongly extrapolating it would provide an air tight barrier at in this instance.

Just wondering if anyone can comment on EDPM performing as an air tightness tape/layer? I've used Illbruck EDPM membranes and associated adhesive for various external waterproofing details and found it to be a useful and adaptable solution. Its not the prettiest of solutions but for this detail aesthetics don't matter so it seems in my mind it may be a good option.

I have a wall to suspended floor junction to seal and wondering if anyone can recommend a specific tape for it. As usual there appears to be a multitude of options available. The tape will be located well behind floor and wall finished surfaces so it need not be plasterable, however the wall has received a parge coat and is unevenness so perhaps some additional tube if sealant will be required. Pro Clima Contega Solido SL seems like it could be an option perhaps other less expensive options would be suitable. TIA for any recommendations.

I actually have found a back to back frame and cistern here, didn't know they existed but looks like a good option where space is tight. Good luck with the planning.

@garrymartin I now am attempting to solve the back 2 back concealed frame challenge, and very appreciative to find your post, as even Geberit themselves seem to be hiding this fitting from the public Can I ask if where you found the Back to back frame diagram above as it doesn't appear on the product page on the Geberit website? Did you actually fit two frames back to back

It is work but, work with a return (although it may not be a necessary return) I'd add dealing with tyre kickers on market place is more work, certainly more painful!

Only difference I have with my cellar vs your garage is the cellar is damp, not very but not bone dry either. Although I guess the PIR wont be able to trap any dampness within the floor build up, that is the main concern I have.

Due to a IWI spec change I now have a lot of 40mm and 60mm PIR sheets that need either reselling or using elsewhere in my renovation. There are three potential situations I think they maybe be used as additional ceiling insulation fixed directly to the underside of GF joists (cellar ceiling), 1st floor joist (GF rooms ceilings) and 1st floor ceiling joists (1st floor rooms ceilings). The original plan in all these instances was to solely fit rockwool between the floor/ceiling joist, given its characteristics (easy of friction fit, acoustic and vapour open) and I still do that at the very least. Overboarding with PIR prior to plasterboarding will obviously increase thermal insulation performance but are there any drawbacks? Obviously ceiling height will be reduced but I have high ceilings and regardless lowering them in bedrooms and cellar is not a big loss. I have never seen PIR used in this situation so would appreciate others opinions. And just to add I don't plan/want to batten behind the PIR prior to plaster boarding unless necessary. Or go to the faff of taping the PIR joints to provide a VCL layer, which I don't think is required here.

If anyone can recommend a good heat & plumbing contractor with experience (and who regularly does such work) of full system installations a DM of their contact details would be great appreciated. Added to the usual pain of finding a competent contractor, I'm finding it particularly difficult as the usual channels for recommendations only return plumbers who seem to focus on boiler servicing and leaky tap repairs. In my experience those contractors who focus on that work dont have the interest in committing to a project that will last longer than a day; they prefer to get in, out and paid the same day and some don't have the knowledge of putting a full system together. Or if anyone knows a register/resource, or any pointers indeed, to find this type of contractor that to would be greatly appreciated also.

@mjc55 I'm just referring to a liquid applied roof covering. I used Restec Flexitec 2020, it is a flexible grp membrane @IcevergeJust came to mind that the breather membrane is probably there to catch any drips that pass the primary covering, its position directly over the PIR which serves as a VCL threw me.

@Iceverge interested to know what the purpose of the breather membrane is here? I've just completed a warm roof, I would describe it as the conventional build-up. Roof covering (liquid in my case) 18mm osb (Thermally broken fixed into joists) 150mm pir Alutrix vcl 18mm osb Roof Joist Plasterboard and skim (Yet to be completed) I did reasonable research before opting for this build-up but after going through the process of assembling it together a number of drawbacks/shortcomings became evident I will not use this particular design again. I'll post a full critique when I get a moment.

Typically you would pattress out areas of wall that are going to have fixtures prior to plaster boarding

Interesting take on IWI solutions from British Gypsum, (I've based the studwork from this spec). The most recent version of their GypLyner Independent System incorporates Isover Steel Frame Batts; however in a previous version from a couple of years ago they were pushing PIR as the insulation, interesting to wonder if this indicates a move towards a more vapour open solution? I imagine BG are specing Isover Glass fibre (and not mineral wool) is due to them both being owned by St Gobain. I wonder what are the vapour permeability performance of glass wool, Isover claim "Achieves Eurofins Gold certification, the highest accreditation for indoor air quality" whatever that means. May give them a call to hear how breathably they believe it to be.

I called Rockwool tech dept with some queries. Asking whether Rockwool can be bonded/adhered to brickwork, (specifically to ensure it stays against the wall as wood fibre can) the response was no it can't as it would delaminate. Furthermore the advice was not to use RW in this situation as there would be a condensation risk if the batts were not held tight against the wall, the person I spoke to went as far as to advise to use the "alternative insulation I mentioned" i.e wood fibre. They did however confirm that Rockwool is breathable and entirely suited to installation in older properties, so a mixed response, maybe even a confused response... Regardless I worked up the build up below using Rockwool: Gypframe 48mm "i" studs fixed floor to ceiling at 600mm c/c without intermediate support "i" studs stood off existing brick wall by ~20mm 75mm RW45 can only be obtained in 600mm wide batts, hence studs at 600mm c/c rather then the more robust 400mm c/c RW45 is fitted tight against the existing brick wall, ~20mm of insulation behind studs to eliminate cold bridging, Friction fit of insulation batt around the "i" profile of studs keeps the batts in position

Yes I had considered doing that, I have plenty soft sand on site so will mix up a 50/50 sharp/soft gauge tomorrow. I suppose given that the parge wont ever see weathering soft sand will be OK, it may even fill the finer gaps.

Thanks for all the input @Iceverge @Mike @Redbeardand all others, very appreciated. So WRT a smart VCL, the jist is that even small gap in the VCL will leak much more domestic bourne moisture into the wall buildup through air movement, than the VCL can return back into the room through vapour diffusion? Therefore an imperfectly installed VCL* (smart or standard) hinder the drying ability of a vapour open wall built up. *Agreed here the reasonable assumption that a perfectly retro-fitted VCL is a unicorn.

Re the parge coat I had in my mind that it would show up any gaps in the mortar joint we had missed with our initially pointing pass, and it has illustrated a few so perhaps we will give apply a second parge coat over what has been done and apply thicker going forward. Perhaps I should have specifically stated my plan was to use the Itello plus membrane rather than saying a vcl; is Intello Plus a vcl? Regardless I had in my head the inclusion of the Intello Plus as a supplementary layer, added in the understanding that it will not completely eliminate vapour diffusion into the buildup, it will leak but it will also allow drying to the inside.

I think this is a good build up. One potential issue I'm trying to get my head around is how/will the stud work keep and maintain to keep the insulation against and in full contact with the wall. The perimeter edge of the insulation boards wont always align with the stud centres and where they dont line up wont the whats keeps the insulation against the wall? Perhaps the second layer of insulation between the studs is necessary to ensure the first layer closest the wall stays against the wall. I've nothing against the cost of doing a WUFI analysis but I'm concerned it will be another case of "this or that" "may or may not" work. I'd rather just assume a vcl is needed and fit it. I imagine it could be double sided sticky taped to the metal studding and then plant on batten on the metals studs to create the service cavity?

Studwork as required as the current preference irrespective of insulation choice is to plasterboard and gypsum skim finish the walls. Reason being I can do the boarding myself and then it should be easy to find a decent plasterer to do the relatively straight forward job of skimming (verses finding a lime plasterer) Ahhh, you think the parge coat may crack, is that because you think its too thick or too thin?

Update on applying the parge coat. We were applying using a sweeping brush to apply direct from a tub but finding that each dip pulls a greater amount of water and lime out of the tub which results in the mix remaining in the tub becoming progressively sandier. Initially mix was a full belle mixer gauge worth at 3:1, however we are having better results with a sightlier more lime rich mix and mixing smaller batches with a paddle mixer in the tub. Now the sand stays in suspension in the tub almost long enough to get it all used. Still undecided about which insulation to use. I'm actually now reconsidering using wood fibre boards now, for a specific reason I want the insulation layer positioned behind the studwork so the insulation is a continuous layer, however the difficulty is then how to keep the installation tight against the wall, as the studs only will only hold what is directly behind them. As wood fibre boards are typically bonded to the wall with adhesive they will stay in place against the wall regarding of studwork. Does anyone know is rockwool batts can similarly be bonded to the wall and if so with what type of adhesive?

As I said there is seemingly no consensus on the correct mix, but the majority suggest NHL 3.5 so that's what I went with. Open to correction but with the parge coat thickness on the wall ranges from 1mm to 3mm I imagine at that thickness using NHL 2 or 3.5 is a moot point.

Finally IWI has commenced onsite. The good advice given here has me sold on the benefit of a parge coat. I think no matter which IWI system you select a parge coat will sit very comfortably in the mix, its effectively the same material as a victorian brick wall (sand and lime) so little concern about introducing non-compatible materials that the building may reject. We have spent a few day pointing up the bigger gaps in the jointing, will parge now and expect much like a mist coat it will show up which areas need further attention. I'm mixing 3:1 Sharp sand to NHL 3.5. This mix seems broadly accepted to be OK, however I've seen @Iceverge add a shovel of cement and elsewhere others say NHL 3.5 is too strong, so again noo hard and fast rule it seems. I will say that its not as easy to put on as I thought, not in terms of hard physical effort but getting it from the bucket to the wall. I'm applying with a soft sweeping brush, the mix in the bucket need to be constantly agitated to keep the sand in suspension, or else you end up just whitewashing the walls. A lot of material goes on the floor, which when gathered and put back in the bucket dries the mix and so more water is required to bring the mix back to a brushable consistency. @Redbeardsuggested a pre-bagged mix which certainly would be an easier material to work with, but I figured I'd need 50+ bags so it works out to be a much more expensive option for my project. Here's how the first gauge is looking.