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Liquid VCL on blocks prior to Plastering


MikeGrahamT21

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Hi,


Just wondering if anyone has been here before, and done anything like this.

 

My initial plan was to use blowerproof liquid as a whole wall VCL (we have external wall insulation EPS on this part of the house, cavity wall construction with cavity filled), to stop the water vapour passing through, and getting trapped, or semi trapped at least. Its quite expensive, but seemed to do what I needed. Now they seem to have changed their advice, and say it needs a grit coat over the top of it, something like feb bond blue grit, before plastering.

 

Thought i'd look a bit further afield, and found Everbuild BlackJack D.P.M, which is a 2 coat solution, and is suitable for application to walls as a plaster bonding agent, and throw sand on the second coat so its ready for plaster. Only problem with this is there is no vapour permeability values, I've emailed everbuild to see if they know.

 

Obviously the everbuild product is a lot lot cheaper.

 

Any insight would be greatly received.

 

Regards

Mike

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everbuild just replied, they don't have any values for water vapour resistance or an Sd, so i'd be going in blind, whereas the blowerproof does have a tested value. Surely a DPM product would stop vapour passing though?

 

Blocks have been painted with emulsion, would that be an issue? i would imagine DPM paint will stick. Its not flaking in any way, was an interim measure so we didn't have to look at horrid grey blocks, wish id not bothered but whats done is done.

Edited by MikeGrahamT21
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I'm using blowerproof in my house, wasn't aware of the change in advice with regards to plastering but then I'm boarding and then plastering so hopefully it'll be ok. Also only doing corner junctions, wall/ceiling , floor/wall and any cracks anywhere in mortar or aerated block. It certainly works and has made a difference in my lounge and its still bare blockwork in the offending cold corner. I used foam first for the larger gaps and adhesive/sealant and then blowerproof

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Yeah I just noticed the advise had changed on the blower proof website, but even on the same page there was conflicting advice, as though they’d only just made the change. Have you ever used blackjack? Long shot I guess, just wondering how the 2 products compare?

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I think i may have found a better solution, which I have actually used before as a tile backer board... Marmox Multiboard (in fact i've still got some of it left!). They're not stupidly expensive, and I'll save me on a few bags of expensive plaster, which can be replaced with cheaper board finish.

 

I never realised you could use it in place of plasterboard, but more importantly it has the insulation layer, which is closed cell, with an Sd value of 3m, perfect for what I want!

 

Thinnest they do now is 4mm (i've emailed Marmox for recommendation), which is suitable for dry lining, and its also ready out the box for a plaster skim according to their website. and I'll use some BAL white star tile adhesive to fix to the painted blocks (unless someone can recommend a better tile adhesive for the situation?).

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Just been and had a look how well bonded the paint is, stuck some airtight tape to the wall and pulled it off, and some of the paint did come off, not sure if that is OK or not. I could rough the surface up with a very coarse sanding board I've got, which should provide enough key, or just put a test spot of adhesive on, and see how easy it is to get off. Ideas?

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Yeah, this is a grit sanding board, very coarse indeed. I bought it to sand down the joints of the aircrete blocks as we used thin joint method, so its probably about the same as you say. To be fair its done a good job, i'd say we have around 30% exposed now, and any bits I've missed i'll pay close attention to individually. Hard to see how much i've done because the bloody adhesive for the thin joint is white and the paint is cream! lol

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