Iceverge Posted July 28 Posted July 28 On 25/07/2025 at 16:18, Annker said: Yes similar setup to your arrangement. The brackets are needed for that particular system though, as the studs are gyplyner type not C or I type. I actually called Rockwool tech dept with a couple of questions. The fella I spoke to recommended/was insistent that in IWI usage the rockwool batts are friction fitted between studs and that the studwork (and batts) are both stood 25mm off the existing brick wall. In effect creating a 25mm (unventilated) cavity space. @Iceverge in the example you shown earlier I understood that the rockwool batts were pressed up tight against the existing brick work. That arrangement makes sense to me, as otherwise the unventilated cavity is created and that seems like an environment where condensation could potentially form. Whenever I speak to product tech depts I invariably think I should not have bothered calling! Correct, no gap. It's a bad idea as it will allow internal air to circulate freely and condense on the internal face of the existing wall causing damage. Espically at joist ends. 1
Annker Posted July 28 Author Posted July 28 8 hours ago, Iceverge said: Correct, no gap. It's a bad idea as it will allow internal air to circulate freely and condense on the internal face of the existing wall causing damage. Espically at joist ends. Understood, that makes sense to me.
mistake_not Posted Thursday at 06:46 Posted Thursday at 06:46 Slight tangent. What paint are you / folks finishing IWI like this with? I'm looking at using something breathable which rules out the normal vinyl Matt etc I think.
SimonD Posted Thursday at 08:27 Posted Thursday at 08:27 1 hour ago, mistake_not said: Slight tangent. What paint are you / folks finishing IWI like this with? I'm looking at using something breathable which rules out the normal vinyl Matt etc I think. I've used mainly Auro clay paint as it's ultra breathable, but there is also Earthborn clay and I've recently found a new company that does clay pain called Coat (not tried them). Auro clay paint is sprayable so very helpful in that. The normal Auro paints are also breathable but nowhere near as much as the clay versions. 1
Redbeard Posted Thursday at 08:58 Posted Thursday at 08:58 If low cost is of the essence then 'contract matt' (once used by volume builders, AIUI, to allow painting a bit 'too early' over plaster - perhaps less so now with taped joints) is probably the one to go for. As @SimonD said, avoid anything with Vinyl in the title (and I think, but don't have evidence to prove, that anything 'silk' may/will be less breathable. 1
torre Posted Thursday at 10:35 Posted Thursday at 10:35 We've used Keim paints for breathability - excellent but expensive - with lime plaster. As it sounds like breathability will be limited here by gypsum boards then as @Redbeard suggests, trade matt is probably a decent choice 1
Iceverge Posted Thursday at 12:15 Posted Thursday at 12:15 I'm a fan of this for allowed walls to dry. Resembles a thin layer of chalk almost when dry. Easy to touch up too and it's dirt cheap. 2
mistake_not Posted Thursday at 15:31 Posted Thursday at 15:31 3 hours ago, Iceverge said: I'm a fan of this for allowed walls to dry. Resembles a thin layer of chalk almost when dry. Easy to touch up too and it's dirt cheap. Before I have just used contact matt as a mist coat, but realised with some modern paints to need to use the right base coat / primer as some folks have had issues with contact matt as a base coat and paints peeling.
Mike Posted Thursday at 18:30 Posted Thursday at 18:30 10 hours ago, SimonD said: I've used mainly Auro clay paint as it's ultra breathable I'll be using clay paints too, for the same reason.
Iceverge Posted Thursday at 18:54 Posted Thursday at 18:54 3 hours ago, mistake_not said: Before I have just used contact matt as a mist coat, but realised with some modern paints to need to use the right base coat / primer as some folks have had issues with contact matt as a base coat and paints peeling. True, I reckon you could literally scrub it off the walls if you had a scourer.
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