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Help, Trying to insulate a thin wall.


AdamSee

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Hi Everyone.

 

I started a post quite a while ago about renovating a 1930s Semi and its all been going horribly really well, and I've finally had to turn my attention to a certain piece of the house that I've been procrastinating over for a while. So the front of the house has a bay window up and downstairs, the downstairs wall below the window is a brick cavity wall which was cavity filled some time ago. But the upstairs is a timber frame with brick infill and plaster which has tiles hung on the outside. I know for a fact that this wall is going to be cold in the winter and is bound to suffer with condensation. So I've spoken to a few people about external insulation and the general consensus is that my best option is to insulate internally. But as to how I do this, is debatable. 

 

My plan was to make the wall air tight first (there are a few movement gaps from where windows have been changed in the past) build a stud wall upstairs and stuff it full of mineral wool/left over cavity insulation and then seal wrap it in a air tight VCL before plasterboarding it. I know celotex would be better, but the shape to fill would be a trapezoid and your trying to fit it through a narrow gap first, so its not practical. On further research, ive found that if theres any slight gap in the VCL, moisture would get in and rot things out. and considering that I was going to make this stud wall extend down through to the lower window and attach to a RSJ, making the VCL perfect seems impossible.

 

So....any helpful thoughts or ideas? Do I persevere and make it work and potential risk moisture getting in, or just insulate upstairs. These sort of things infect my dreams these days....

 

Downstairs looking up

1929809623_Downstairslookingup.jpg.ddf2d3352257a055cc4b910f85c89186.jpg

 

Upstairs looking at the bay and cracks where the timber frame starts

2127704558_Upstairsbrickwork.thumb.jpg.b4b0cd95b6635ede14eb0e7ca8d3a96a.jpg

 

Look up from downstairs at where the RSJ meets/goes in to the cavity

645693494_Downstairsceiling.jpg.691f8335c7c6b3ba568c55789cce63e2.jpg

 

The upstairs bay.

Upstairs.jpg.7a1d10c6b98b4407ec778feed5404ae3.jpg

 

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As you can see, there is not a lot holding the bay up. Basically the outer edge of the bay floor sits on top of the downstairs windows hence why it's a lightweight wall.

 

Usually the original downstairs windows are built to give some structural support. Not all replacement window companies seem to know that.

 

I think you are on the right lines with your proposal, Make a timber frame, I would go 1 frame member in line with each window joint.  I would then bend a sheet of plasterboard around it.   Cut it to the width of the strip, then leave it leaning against a wall for a while, it helps to wet it, and it will take up somewhat of a curve.  Fit it while still damp so it bends and conforms to the curve you want.  Don't put the screws in any more than just nipping the board until it has had time to dry in place.

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Loving that idea to keep the curve, may have to go down that route and see how it works out. The stud wall idea is only going to be made from 2" x 4" so there isn't going to be much insulation in there, so i was planning on going over the top with say 40mm insulated PB so I was prepared for it to be faceted. Your right about the window taking some of the weight and the original timber windows would have been load bearing, were currently awaiting new bay windows to be installed but there still weeks away and there now designed to be load bearing.

 

I'm just unsure as to weather I'm being paranoid about moisture getting in to the insulation and not escaping causing the frame to rot and I definitely have no idea about things such as "dew point" and how its affects things. Its pretty much the 2nd to last major job I have to do before I finish off the front of my house, and really don't want to bugger it up by rushing it and not thinking it through.....or over think it and not get it done at all.

 

 

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In theory you could slit Celotex to get the curve and fill with low expansion foam. THEN cover with bendy pb. Sort of thing I'd do just to see if I could...

 

:ph34r:

Edited by Onoff
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Well had abit of a development earlier. Alot of the plaster on the wall was blown and so I though before I do anything I should strip it back and either patch it up or re plaster it. Well it pretty rapidly all came off and left me with this. So you can now easily see how the wall was constructed and there's one thing for sure, this ain't air tight. There's quite the breeze coming through which isn't a surprise considering there big gaps around all the timbers and a brick missing in one spot to which you can see the outside tiles through.

 

So where do I go from here? Obviously the hole needs refilling with another brick. But whats the best way to reseal it all up before insulating? I've got left over plaster over air tight tapes and paints. Pretty lost with this one. IMG_20180817_184934069.jpg.20a4d287a47f83de3756791d4cfa3c0e.jpgIMG_20180817_184951235.jpg.0cab8dd21e732dd783203d57d4d8d7fe.jpg

IMG_20180817_184941932.jpg

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Fit missing brick then parge coat. then new timber frame as before with air tight layer before plasterboard.

 

The house I grew up in (my sister still lives there) I am sure the upstairs bay wall is just timber and lath and plaster. Render on the outside, plaster inside. Held together now I am sure by many layers of wallpaper. Almost certainly no insulation.

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Reminds me of a pub I'd drink in as a youngster. Close boarded outside wall with a shrinkage gap between every board. Massive overhang on the dimly lit bar. If you were lucky you'd get "nuzzled" by the giant Alsatian hiding in the shadows as you ordered a round. Broke my heart when they did the place and knocked the two bars into one.

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16 minutes ago, Onoff said:

Reminds me of a pub I'd drink in as a youngster. Close boarded outside wall with a shrinkage gap between every board. Massive overhang on the dimly lit bar. If you were lucky you'd get "nuzzled" by the giant Alsatian hiding in the shadows as you ordered a round. Broke my heart when they did the place and knocked the two bars into one.

Was that during the war?

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1 hour ago, ProDave said:

Fit missing brick then parge coat. then new timber frame as before with air tight layer before plasterboard.

 

The house I grew up in (my sister still lives there) I am sure the upstairs bay wall is just timber and lath and plaster. Render on the outside, plaster inside. Held together now I am sure by many layers of wallpaper. Almost certainly no insulation.

2 hours ago, Onoff said:

I see da light! :)

 

Mesh & parge coat maybe?

 

Im pretty sure this was held together with wall paper as well. The combination of that and the plaster skirting was definitively doing the job.

 

Thanks for the tips folks, pretty sure I've got a roll of wire mesh around for this that will work. Can bonding/hardwall coat be used as a parge coat or would i be best with a sand/cement render mix? I have used soundcoat as a parge on nearly all the walls downstairs, but the stuff is quite hard to come by around here, not sure why, but cant just pick the stuff up on the Saturday morning shop and typically, i'm all out of it now.

 

Edited by AdamSee
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I would consider a custom furniture item to avoid too much buggeration with the wall.

 

I might consider something pushed up against it or fixed with removable screws or wing nuts so I could look behind, and perhaps a ventilation space.

 

Sheet box or toy box or similar?

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5 hours ago, PeterStarck said:

If there was a way to keep an even thickness I would be tempted to use a spray foam, such as Icynene, which would solve the airtightness and insulation issues in one go.

 

Spray insulation sounds like a viable plan, would be good for where the wall continues through the floor and joins up with the wall cavity and RSJ. 

But why does it need to be a even thickness? With the current shape and the stud wall that will be made im probably looking at a difference of 50mm on insulation thickness.

Edited by AdamSee
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Been looking in to spray foam and currently wondering if anyone's used it or know people who have used the kits from Foamseal? 

 

Started building the stud wall and realised that it would be considerably easier if I had a floor in place at the moment. Minor dilemma mixed in with usual procrastination, apparently there are two different types of spray foam, open cell and closed cell, the closed cell doesn't need a VCL but the forma does. If the floor is in place already I cant fit the VCL and because of the type of floor im using, i cant exactly attach it to the floor for various reason. But either way, without knowing what type of spray will be used I guess im just going to have to make the wall first and be prepared to seal it up. 

 

It took a few minutes for me to realise that I had answer my own question. So.....here are some pics.

 

Floors up, bricks back in place, bottom of stud wall coming together, think I may level off the joist before going much further. Its not that ones out of places, its that its actually smaller and ones bigger. 

IMG_20180818_163655520.jpg.9e08d0693b72049bcdd32a4362611f66.jpg

 

And here's all the flooring for upstairs which arrived not too long ago, 22mm t&g chipboard flooring pre-routed for 12mm UFH pipe to be laid in. This actually forms part of the structural deck. Its very sad, but I'm unbelievably excited about getting this in.

IMG_20180818_163709226.thumb.jpg.fb5dc1fb84b63171d25109ecacbe86f5.jpg

Edited by AdamSee
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10 hours ago, AdamSee said:

 

Minor dilemma mixed in with usual procrastination, apparently there are two different types of spray foam, open cell and closed cell, the closed cell doesn't need a VCL but the forma does.

 

That's not quite right. Icynene is open cell and the company will carry out an interstitial condensation analysis for your wall construction to see if a VCL is required.

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