Vapour membrane on outer wall & third-leaf question!

[tombarton]

Hey team, hopefully this gets more traction than my last third-leaf question!

I'm adding a vapour membrane to my outer wall, as the current room has some moisture damage. I'm worried that having a small air gap between the membrane and the outer cladding will create a third leaf in my wall system.

See this image:



The exterior surface will be concrete sheeting (blueboard). Then a layer of vapour membrane (Bradford Enviroseal for those playing at home). The manufacturer recommends putting some space between the outer layer of the membrane and the exterior cladding, so moisture can roll down and out. This is done with some small railings, which I've drawn way bigger in the diagram.


My worry is: if I cut plasterboard to fit the stud gaps for the wall, I may get a third leaf happening between this plasterboard and vapour membrane, and the outer cement layer. As there will be another internal wall made for the room-in-room method. e.g., would be studio wall -> second wall -> outer cement later.

Any thoughts?

 

[mjbphotos]

Cement sheet as an exterior wall? Never heard of that. Also never heard of an exterior vapor barrier that needs space between it and the outer cladding.

Why wouldn't you just put the plasterboard on top (not in between) of the studs? Trying to put it between the studs would be difficult, and not practical as far as I can tell.

 

[TAE]

Cement sheet as an exterior wall? Never heard of that. Also never heard of an exterior vapor barrier that needs space between it and the outer cladding.

Why wouldn't you just put the plasterboard on top (not in between) of the studs? Trying to put it between the studs would be difficult, and not practical as far as I can tell.

I'm assuming this is in EU not USA based on the building material terms used. With regard to cement board MJB you may not be aware of it but much of the siding being used today is cementitious. James Hardy has been making cement based siding for 20 + years also a tile underlayment called Hardibacker. Here in the states the most common vapor barrier is Tyvek from Dupont and the siding be it cement or wood is applied directly over it no spacing in between. By installing the cement board directly on the vapor barrier you eliminate one of the leafs.....

HERE is a great article on soundproofing and discuss's the pros and cons of triple leaf and that it is not always a bad thing....

Good Luck!

 

[TAE]

I've been watching homes get built since I was @ 5 years old here in California (Pops was a hardwood floor man) There is more than one way to skin a cat...some ways better than others and some just wrong. On the siding and Tyvek or any "Vapor / moisture Barrier man things have evolved..so after reading the original post I started going out on the net looking at what is recommended....a lot of ways to go about it for sure...Here in Cali I have seen a lot of siding put right on the tyvek no spacing but it appears that is not the case where it gets colder or wetter....hmmm...

Here's a fun video on siding at the 2018 Builders show ..I attended but was not paying attention to siding or vapor barriers I was just bird dogging countertop materials

2018 Builders show

 

[tombarton]

Cement sheet as an exterior wall? Never heard of that. Also never heard of an exterior vapor barrier that needs space between it and the outer cladding.

Why wouldn't you just put the plasterboard on top (not in between) of the studs? Trying to put it between the studs would be difficult, and not practical as far as I can tell.

Rod has recommended on several forums that if you're starting with a room that's already plastered (and you'll have to remove it anyway), you can gain extra outer wall mass by sawing the plasterboard along each stud, then pushing it into the stud hole and affixing/caulking. This doesn't replace the inner plasterboard that either gets hung of resilient clips, or a second inner wall frame.

[MENTION=1094]TAE[/MENTION], recommended in Australia (so don't know why it wouldn't be in US), to have a gap between vapour barrier and external cladding: Installation instructions (see page 2 diagram)

 

[mjbphotos]

Rod has recommended on several forums that if you're starting with a room that's already plastered (and you'll have to remove it anyway), you can gain extra outer wall mass by sawing the plasterboard along each stud, then pushing it into the stud hole and affixing/caulking. This doesn't replace the inner plasterboard that either gets hung of resilient clips, or a second inner wall frame.

That's an insane amount of work! And you've got to pull off the pieces of plasterboard still affixed to the studs, too?

 

[witzendoz]

I would get the opinion of a professional builder, actually I would get a builder it to solve the moisture problem and then build the studio.

Alan.

 

[TAE]

Man I am nearing that impasse where I have to figure out what I will do with my interior walls and ceiling in my music room and all I can say is Damn! This shit can get expensive quick!

Just finished fitting / trimming (2) 36' wide solid core doors HEAVY by myself...note to self.... this is not a one man job dummy!