Best Practice For Internally Dry Lining a brickwork wall

Blisterman

Looking at dry lining an interior wall. Currently it's solid Edwardian brickwork to the exterior with a solid layer of what I think is original plaster inside.

My thoughts are as follows:

Strip back the paint on the existing plaster.
Fix a breather membrane to it
25x50mm battens on that.
70+12.5mm dry lining board made air tight as much as possible.
To achieve 0.24 U Value.

In principle this would allow any moisture that penetrates through the brickwork or condenses in the batten cavity to diffuse back out through the plaster and brickwork.

Removing the plaster would be a nightmare, and probably damage the brickwork, hence why I'm trying to avoid that.

However, other guidelines I read advise on an airtight membrane to the inside face of the brickwork to prevent any moisture getting in from the outside. My fear with this is that inevitably in an old house, I'll never get it completely airsealed and some warm air will get behind the insulation and condense. With nowhere for this moisture to go, it'll lead to mould.

Other advise has been to dot and dab fix the dry lining to the existing plaster, leaving minimal airspace between the old and new for condensation to occur.

I'd be interested to hear other people's opinions and experiences in this.

Dudda

I'm not an expert on this but I think this is the wrong build. If it's original wall, original plaster, breather membrane, cavity with battens, insulated plasterboard then the moisture will be between the original plaster and breather membrane. Cavity does nothing except allow thermal looping behind the insulation.

If it's original lime plaster it should be easier to take off although messy. If it's cement it's a lot harder. You sure it's original as if it is this allows the walls to breath. Cement doesn't.

I think you need original brick, original plaster, 100mm breathable insulation (mineral fibre, wood fibre, sheeps wool, etc), vapour control layer. 25mm timber battens to create service cavity which can be filled with more insulation and then plasterboard with skim finish. You can modify the numbers to suit. The key is it's all breathable layers to allow it to dry out but it's also airtight and warm.

If you want to go non breathable insulation you'll need an interstitial condensation test done. This confirms where condensation will occur in the wall. You can get this done for free from a lot of insulation suppliers. eg if you order the breathable insulation from the Ecological Building Systems they'll do the test for you. I've also got Kingspan and Bauder to do them for me in the past. I presume Xtratherm also do it.

Have a look at other similar brick buildings on this website.
https://passivehouseplus.ie/magazine/upgrade

sydthebeat

Blisterman wrote: »

In principle this would allow any moisture that penetrates through the brickwork or condenses in the batten cavity to diffuse back out through the plaster and brickwork.

no.

breather membranes (vapour control layer) allow vapour through, but not moisture.

Therefore any moisture formed by condensation on the cold side of the insulated plasterboard will be trapped, in an area of organic material (wood) which is unventilated and ripe for mould growth.

You also have the problem in that construction of interstitial condensation forming in this area during those hot summer days where outside temperatures are significantly higher than internal and the energy flux is from outside to in, causing vapour to condense internally.

in order for that construction to work, you either use a breathable construction internally (breathable insulation, paper backed plasterboard, breathable paintwork).... or you try as hard as you can not to allow vapour into the wall with foil backed plasterboard, non breathable insulation and a vapour barrier against the existing wall.

The latter is very hard to do unless your doing an extensive renovation including new floors etc

Calahonda52

OP, without knowing the exact wall construction here, you are asking for trouble so in the absence of full knowledge, you need to err on the side of caution and iff you decide to proceed, go with the fully breathable route for the reasons outlined above.

I just would not do it, focus on things like uncontrolled ventilation etc

The key spec is establishing the internal finish: is it painted with oil based paint?
Is it a lime based plaster?

Wartburg

In my honest oppinion - an insulated plasterboard (with or without counter battens) has no place on a solid brick wall.
What´s the point of having a breathable membrane installed, by having a more vapour tight layer (brick) behind on the way to outside?
Create a heating concept which uses the massive thermal mass potential of your solid brick wall instead of chasing for theoretical u-values.

DOCARCH

For a solid brick wall, a breathable dry-lining system is required. Google Calsitherm or Optima Dry Lining

Wartburg

DOCARCH wrote: »

For a solid brick wall, a breathable dry-lining system is required. Google Calsitherm or Optima Dry Lining

And come (ideally) to the right conclusions please.

No.1 - Calsitherm (and all other calcium silicate boards)

As coming from the Calsitherm website:

Working principle
The temperature difference between indoor and outdoor climate causes ingress of water vapour into the structure. This phenomenon is reinforced by an internal insulation. Particularly in the case of diffusion open systems, there is a measurable moisture development on the cold side of the insulation material.
This condensate is absorbed by the capillary-active Climate Board, transported to the inner surface and from there it is released into the air in the room. The short-term absorption of the temporarily high humidity (for instance, after showering) creates the comfort that the CALSITHERM climate board is famous for.

Releasing moisture back into the room air requires a certain capacity for adsorbing water vapour through your room air. What happens in case she´s too cold or already saturated? In the worst case you´ll see mould growing even on your highly praised calcium silicate board.


No.2- Optima Dry Lining

Nothing else than glass wool, obviously "refined" as a "certified" (NSAI) and "complete" system for internal insulation. Glass & mineral wool sponges up condensation and creates a nice source for permanent dampness in your structure. Perfect for breeding dry rot in case you have some timber somewhere in reach.

Blisterman

Thanks for all the feedback. Lots to chew over.

Looking now at this wood fibre insulation:

http://www.pavatex.com/en/products/wall/pavadentro/

Has anyone any experience with it?

booooonzo

Blisterman wrote: »

Thanks for all the feedback. Lots to chew over.

Looking now at this wood fibre insulation:

http://www.pavatex.com/en/products/wall/pavadentro/

Has anyone any experience with it?

I've done a room as a test in gutex woodfiber, 60mm I used.
Then i used lime green solo plaster and breathable paint.
Came out ok but too expensive all in and fragile I think.
Will probably use the optima system going forward.

Lumen

Ventilate the cavity you're creating to the outside or use a fully permeable build up.

Vapour control on warm side of insulation.

Calahonda52

booooonzo wrote: »

I've done a room as a test in gutex woodfiber, 60mm I used.
Then i used lime green solo plaster and breathable paint.
Came out ok but too expensive all in and fragile I think.
Will probably use the optima system going forward.

Did you use any mesh with the plaster?
I have never seen wood fibre plastered without a mesh
.
it adds a lot to the strength

Lumen

Since there's mention of brand names already in this thread, Pavatex might be worth looking at. It's not a recommendation as I haven't used it yet, but they do various composite panels.

There are some cross-sections and manuals linked here (and presumably elsewhere):

https://www.natural-building.co.uk/system/internal-wall-insulation-lime-plastered-finish/

I think that plain woodfibre is NOT hygroscopic or capillary in action, so (for instance) doesn't deal well with surface water, whereas calcium silicate boards do (albeit at greater expense), so I can see the appeal of a composite solution if there's a risk of condensation forming on the back surface.

booooonzo

Calahonda52 wrote: »

Did you use any mesh with the plaster?
I have never seen wood fibre plastered without a mesh
.
it adds a lot to the strength

Yes mesh used also , plasterer reckond it was nice but harder than he expected to work.

It's a pity of the price and lack of grants for more natural insulation methods as it is nice and more healthy etc..