Applying gyproc soundcoat plus

[Malc]

Gyproc seems to have very little info on how to apply this so what do peeps here think?

It's 6mm thick so by eye or wood strips to get right thickness?

It says 17.5 l of water to a bag, exact or does that needs adjusting for consistency?

Mix and use or mix, wait, remix, use?

On aerated block, wet the blocks first?

Metal tools I assume? Not poly float.

BTW this is for a parge coat rather than for sound although there is one inside block wall I'll probably use it on for sound.

Thanks

 

[chappers]

As a parge coat it shouldn't need wetting up nor flattening out, I've never used the stuff but was under the impression that it still needed a backing coat plaster or boarding over the top, with double check boards.
Yep metal trowel, if your not using it for the reasons its meant for why aren't you just using a regular backing coat and then skimming or just dot and dabbing board to the wall.

 

[Malc]

Soundcoat is dual purpose product, for sound or parge. Or if you say to gyroc what do I use as parge coat they say use soundcoat. I'm going to dot and dab boards over it and will have continuous dabs top and bottom for secondary air tightness.

 

[chappers]

as said if your not worried about the sound properties then just dab straight to the blocks, a parge coat is probably technically the correct thing to do but not sure anyone bothers anymore, at least they didn't last time I was on a big site a couple of years ago.

 

[Malc]

I'm installing a MHRV system. For that to work the house needs to be as airtight as possible, hence the parge coat.

 

[chappers]

fair enough then just crack on. mix as per instructions and slap it on, no need to even flatten it off really, no need to wet the blocks. Last time I saw guys parging the walls they didn't wet the walls and left it pretty rough.

 

[Malc]

Just thought I'd update this thread in case some on the future finds it useful.

My method for mixing soundcoat uses 4 builder's tubs, hawk and float, and a bucket. The instructions say 17.5 l of water to a 25kg bag. I take a bag and split it into 2 builders tubs. I have a set of digital bathroom scales to get this spot on 50:50. I've measured 8.75 l of water into my bucket marked the level with permanent marker. The water goes into the 3rd builders tub and then I add half a bag of soundcoat for a builder tub. Mix with a bucket trowel and then with a power mixer. Mix again with bucket trowel to make sure the stuff is off the sides (this also lets the mix stand a bit, like you do with porrige). Then another power mix to get rid of any lumps. End result is like semi whipped cream, not stiff and not runny, like silicon sealant I guess. I apply this by eye as thick as I can which is not the 6mm thick gyroc says. I dunno how they reckon to get that as it is too thin to go on that thick unless you do multiple coats. It seems the right consistency to me as you want it to go on easy and coat the wall as a parge coat (i.e. to make the wall air tight). It is was stiff enough to go on a 6mm then it wouldn't spread so nicely. I'd say I was getting it on at ~3mm so a bag goes further than gyroc reckon.

 

[Malc]

Having gone through 10 bags of soundcoat what I've found is they vary in weight and you need to vary the water to match. In black plastic builders' tubs 50% of a bag weighs 13.6 - 13.9 kg. 50% of the specified water, 8.75 l seems right for the 13.9kg half bags but the mix comes out too thin for 13.6 kg half bags. With those I've found reducing the water by 0.25 l works better.