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  1.  
    I try and avoid wood and wood products due to woodworm in this old building. I treat every 5 years just to keep on top of the problem.
    • CommentAuthorKenny_M
    • CommentTimeMay 10th 2018
     
    Thanks Rick - all the wood fibre products I have seen have specified Lime or Clay plasters. There is also a pipe that needs to be boxed around in the corner, and the frame as you say helps with securing the shower valve etc. There is an also an element of this is the main bathroom and we have guests coming in June so I need to get a move on, the frame is probably the quickest and easiest way for me to get the place back in action, but to still get insulation in place. For the next rooms to be tackled this knowledge will be handy though - I think in retrospect I would take off the lath and plaster, leave the original plaster on the wall, bond the fibreboards as you say, and not start any of it until I had someone in place who could do the lime plaster!

    Thanks John, As far as I am aware we don't have that problem, fingers crossed...
    • CommentAuthorMike1
    • CommentTimeMay 10th 2018 edited
     
    I've not used the product myself, but have come across literature about Calsitherm Climate Board in the past, which looked to have some interesting properties for internal insulation. May be worth a look, but probably not cheap.

    Looking back through my notes, it looks like I came across it in this comparative study: http://www.josephlittlearchitects.com/content/breaking-mould-5

    The paper's conclusions are interesting too:

    "One striking conclusion of this comparative series of simulations is that higher and higher levels of external insulation appear to create healthy and ever more stable conditions within the wall buildup, while even relatively modest levels of internal insulation face tougher conditions and either failure or are bordering on doing so. An equally significant conclusion is that the right treatment of the external face appears to allow the installation of internal insulation without risk of growth in internal moisture levels."

    ...so you may wish to look at treating the external face of the wall too.
    • CommentAuthorMike1
    • CommentTimeMay 10th 2018 edited
     
    Looking at Joseph's website, this more recent paper may also be of interest, though it focuses on the problem of retrofitting ground floor rooms & I've only just skim-read it: http://www.josephlittlearchitects.com/architecture/inappropriate-retrofits-can-stress-solid-wall-dwellings-sdar-journal
    • CommentAuthorKenny_M
    • CommentTime5 days ago
     
    Thanks Mike, all interesting stuff.

    It's a little depressing really. It seems like the message I am picking up on from a number of sources is don't insulate internally, and as I can't insulate externally I am beginning to wonder if the message is don't insulate the walls at all!

    The article makes a point about sealing the external wall with what I presume is a barrier to rain, but not to vapour, and limiting the u value to around 0.5 to ensure the vapour is driven through the wall inside to outside. I have seen a similar minimum value of 0.6 suggested before for traditional houses, and also a recommendation against insulating the north facing wall to ensure that wall has enough heat in it to drive moisture out.

    The article seems to refer mostly to brick walls so not sure how relevant it will be to my property which is 600mm thick stone. Its actually hard to see how accurate these simulations can be for traditional properties when the construction of the wall is unknown and varying. My house has Ashlar sandstone block on the front, but the sides and back are a mix of sandstone and whinstone, presumably with a cavity of unknown width with unknown infill. The wall I took down in the bathroom had gypsum plasterboard, then lath and plaster, and still had the original internal render on the stone. Add in the voids in chimney stacks to the mix and I can't see a model being very accurate.

    Some of the Historic Scotland research has found in situ u value measurements of 600mm solid stone walls to be around 1 W/m2K, and in some cases slightly lower. If 0.6 is about as low as you can go before entering the risk zone then it hardly seems worth the disruption and risk of making a change.
  2.  
    Posted By: Kenny_MThanks Mike, all interesting stuff.

    It's a little depressing really. It seems like the message I am picking up on from a number of sources is don't insulate internally, and as I can't insulate externally I am beginning to wonder if the message is don't insulate the walls at all!

    The article makes a point about sealing the external wall with what I presume is a barrier to rain, but not to vapour, and limiting the u value to around 0.5 to ensure the vapour is driven through the wall inside to outside. I have seen a similar minimum value of 0.6 suggested before for traditional houses, and also a recommendation against insulating the north facing wall to ensure that wall has enough heat in it to drive moisture out.

    The article seems to refer mostly to brick walls so not sure how relevant it will be to my property which is 600mm thick stone. Its actually hard to see how accurate these simulations can be for traditional properties when the construction of the wall is unknown and varying. My house has Ashlar sandstone block on the front, but the sides and back are a mix of sandstone and whinstone, presumably with a cavity of unknown width with unknown infill. The wall I took down in the bathroom had gypsum plasterboard, then lath and plaster, and still had the original internal render on the stone. Add in the voids in chimney stacks to the mix and I can't see a model being very accurate.

    Some of the Historic Scotland research has found in situ u value measurements of 600mm solid stone walls to be around 1 W/m2K, and in some cases slightly lower. If 0.6 is about as low as you can go before entering the risk zone then it hardly seems worth the disruption and risk of making a change.


    Kenny

    Dont worry about it. I find the secret with my old stone walls of similar thickness to yours is to keep them dry. So only lime mortars and plasters with stone skirting so plaster does not wick. The Lunos MVHR has also been a revelation. Any walls I do replaster I incorporate insulation in the lime plaster mix. Not tried cork as yet. 3G windows direct into the stone mullions has also made a big difference.
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Posted By: Kenny_MIt seems like the message I am picking up on from a number of sources is don't insulate internally

    No, the message is that it's much easier to make a good job of external insulation, so it's generally preferred. There are more things to consider when doing internal insulation and there are usually limits to how much insulation you can use, so it pays to make sure you know what you're doing and understand why.
    • CommentAuthorKenny_M
    • CommentTime5 days ago
     
    John - what do you mean by "stone skirting"?

    Posted By: djhit pays to make sure you know what you're doing and understand why

    The thing is that there doesn't seem to be a definitive right answer. There are a lot of very knowledgeable people on this forum and also lots of different opinions, on this thread alone both vapour closed and vapour open insulation have been proposed. There are also a lot of people outside of these forums who make a strong argument against not insulating these old walls.

    Especially for an old house like this I am more convinced by the vapour open approach, but in a bathroom I am still inclined to try to keep the vapour as much as possible out of the walls, in combination with expelling it. That's starting to make me question the wood fibre I was thinking of, as if I am trying to keep moisture away from the walls maybe I would be better with something like EPS that's not so hygroscopic, maybe more of a barrier to vapour but not a complete barrier if that makes sense.

    My gut tells me I am probably over thinking this, as I am religious about ventilation and monitoring RH levels in the house, but I suppose you only find out if you are wrong five years later when the mould starts growing through the wall... :)
    •  
      CommentAuthordjh
    • CommentTime5 days ago
     
    Posted By: Kenny_MThe thing is that there doesn't seem to be a definitive right answer.

    I agree with you there. That's why you have to know enough to be confident that you've chosen a good, workable solution even when some people tell you that you're wrong. And ideally, you can explain to them why their worries don't matter, or at least believe you don't need to worry yourself.

    My gut tells me I am probably over thinking this, as I am religious about ventilation and monitoring RH levels in the house, but I suppose you only find out if you are wrong five years later when the mould starts growing through the wall

    I have the same tendency. Perhaps one way to look at it is that some people would happily replace their bathroom every five years anyway, so in the worst case if you did have to rip it all out and do it over again, you could just claim to be 'refreshing' your decor :bigsmile: :devil:

    FWIW, I've kept the interior of the actual showers impermeable, where they regularly get sprayed with water, but I've happily left our outside walls breathable in the bathrooms as elsewhere. That felt like a reasonable compromise to me and it seems to be working fine. There's continuous ventilation, of course.
  3.  
    When I first bought the house the mortgage company were insisting i put in a damp course as we had rising damp upto 1 metre high. Turns out it was the lime plaster wicking making it damp. Originally the house was designed to have an exposed stone skirting with lime mortar pointing of about one foot then lime plaster above. Any damp migrating through the stone was dried out by the lime mortar. Since reinstating the stone skirting we have not had damp walls and the mortgage company where satisfied that we did not need a damp course.
    • CommentAuthorKenny_M
    • CommentTime3 days ago
     
    I've never really understood this thing about chemical damp courses. Maybe I am missing something, but I have never bought the idea that drilling some holes and squirting some chemicals in, constitutes a continuous damp course.

    As you found John, usually reverting to the original design is what fixes these damp problems in old houses.
    • CommentAuthorKenny_M
    • CommentTime2 days ago
     
    So spent this evening doing a bit of lime mortar pointing for the first time to fill the holes in the wall before putting insulation on, will finish this over the weekend.

    I am going to go for 50mm EPS, which will be held tight against the wall with my wooden frame on the inside. 50mm EPS seems from what I can gather to be reasonably 'safe' in terms of not going for too low a u value, the calculator I am using seems to suggest this will give a u value of around 0.52, I am tempted to put insulation between the battens too as this would take me down to

    Wickes along the road have these big Kay metzeller flooring sheets of EPS, presume it will be better to have fewer gaps between them so thought this might be good.

    Should I just allow the sheets to but up against each other, or is there a filler/sealer that can be used where there are gaps?

    Incidentally I priced up diathonite, and it was going to be £700 for the materials, for a 10m2 wall, hence coming back to EPS which is about £75 for same, + plasterboard and timber etc, maybe taking me to about £150.
    • CommentAuthortony
    • CommentTime2 days ago
     
    Failsafe design would be tray with upstands or wetroom floor going up behind wetwall panels.

    Not sure you need wood, or plasterboard, what adhesive will you use to fix the eps?
  4.  
    Kenny_M, you missed out a U value (to be achieved by insulating between the studs): '' I am tempted to put insulation between the battens too as this would take me down to...

    Wickes''

    Seriously, I think if 50 EPS gives you 0.52, and you are really concerned (as should we all be) about interstitial condensation, then there's some argument for sticking there. If you did, would your VCL be over the studs over an air-gap? How would it seal at the perimeters?
    • CommentAuthorKenny_M
    • CommentTime2 days ago
     
    I probably don't 'need' wood but I feel more comfortable getting everything straight with a frame as its an uneven wall, and there are a few other reasons, pipes need to box out a drain pipe etc. OH doesn't want tiled room, plasterboard and paint, just tiles around shower etc - will use cement board or similar there.

    I wasn't planning on fixing the EPS with adhesive as such, I was going to use the frame to hold it tight to the wall - although it might be good to have something to tack it in place while getting the frame up.

    I saw an old thread on here about using PU foam, I think to bond to wall and to fill gaps - I take it that is just the stuff you get in a can - this type of thing - https://www.screwfix.com/p/soudal-gap-filling-foam-hand-held-750ml/46137
    • CommentAuthorKenny_M
    • CommentTime2 days ago
     
    Sorry Nick, I think it was about 0.33 with insulation in between the studs and I agree with you that I think this is too low.

    I wasn't planning on having a VCL. I was working on the premise that this is a breathable construction, stone, lime mortar etc, and that although EPS, then plasterboard and paint would limit the flow of vapour from the bathroom it would still allow some transmission.
  5.  
    ''I saw an old thread on here about using PU foam, I think to bond to wall and to fill gaps - I take it that is just the stuff you get in a can - this type of thing - https://www.screwfix.com/p/soudal-gap-filling-foam-hand-held-750ml/46137''

    Yes, and no. You want low-expansion adhesive-grade foam, and ideally to spend 20-odd quid and get a gun. Much less likely to clog up than the DIY cans (although I am told the latter have got better than they were 'in the old days'). Have a look at https://www.screwfix.com/search?search=no+nonsense+sticky+foam. I have just been using it to adhere plasterboard to Pu and XPS.

    I follow your rationale with no VCL, though I am not certain I'd do it with a plastic insulant (but I don't often use EPS - certainly not enough to have got a 'gut-feeling track record' with it). It's a bathroom, though. Isn't it going to end up with vinyl-type impermeable paint (for which read 'VCL')?
    • CommentAuthorKenny_M
    • CommentTime2 days ago
     
    Posted By: Nick ParsonsI follow your rationale with no VCL, though I am not certain I'd do it with a plastic insulant

    In some of the discussions I have had on here about external insulation, many argued that EPS is vapour open. There is that counter that its not as vapour permeable as wood fibre etc, so I was a little uncomfortable about this on the exterior of a stone building, but open to the idea.

    Posted By: Nick ParsonsIt's a bathroom, though. Isn't it going to end up with vinyl-type impermeable paint (for which read 'VCL')?

    Yes, and that's another reason why I didn't think I would need a VCL. I read something a long time ago about insulating old buildings that has stuck with me about getting progressively more vapour open as you go through the layers to the outside, and that seems particularly logical with a room that will be particularly humid. My thinking in this scenario the paint on plaster is an almost VCL, then the EPS semi permeable, then the lime mortar which is fairly permeable and is usually the release valve for moisture on old buildings.
    • CommentAuthorgyrogear
    • CommentTime2 days ago
     
    Posted By: Kenny_Mgetting everything straight with a frame as its an uneven wall,


    you could use metal studs ... ?

    gg
    • CommentAuthorKenny_M
    • CommentTime1 day ago
     
    Thanks gg, but that wouldn't give me the space for services. I'm comfortable with the wooden frame, got the wood and I have the space on that wall. I realise its probably not the best solution but I a under time pressure now to get it back together.
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