gypsum hardwall

[stevegreen]

Could anybody help please - How thick can hardwall be applied to the walls (need to use this to meet u value) and is there any problems with cracking when finished with skim if hardwall is applied to dense concrete blocks.
Has anybody had bad experiences with this product?

 

[Alastairreid]

8-10MM

 

[stevegreen]

Can it be applied in layers to say achieve 20mm.

 

[joe-90]

Why not use a product designed to be insulating? 20mm of plaster would take ages to dry out.

 

[NickB_99]

Can it be applied in layers to say achieve 20mm.

It is intended to be used as an undercoat 8-10mm (as per a/r).
I'm sure it can be built up in layers, but that will be a lot of plaster to mix & spread.
I'd agree with Joe.
Some of the Gyproc boards with insulation are about this thickness and will give you much better thermal properties.
Check out some of the data sheets and do a quick calc.

 

[stevegreen]

I've got dry lining elsewhere in the house and i'm not very keen, this room is going to be a kitchen and when installing fixings for cupboards etc. I want to be able to fasten to the walls with more security than dry lining allows. Does hardwall really take that long to dry out? How long would you say. The insulating properties of hardwall are far better than sand and cement, which is why i've been forced this route.

 

[Micilin]

One or two scratch coats, rule each off so that you can keep the final coat true. Just let each coat set before the next one. You'll have no problem skimming it and just make sure the place is well ventilated. If the background is not wet , should be okay after a week , ten days to paint but it depends on the conditions. You can go up to 25-30mm before you should mechanically fix eml to the wall but I've seen more go on walls with no problems.

 

[joe-90]

You won't be able to paint that in a week. You ask Richard C - he's the Daddy.

 

[Micilin]

No way of telling from here , joe - dry blocks and warm dry air , week or ten days . Wet blocks and no drying obviously longer !

The air movement is more important than heat. Chases and dobbing out will be longer.

I'd rather wait longer for hardwall to dry than have dot and dab or studwork in my house, but that's just preference and presumably that of the OP.

 

[roughcaster]

One or two scratch coats, rule each off so that you can keep the final coat true. Just let each coat set before the next one. You'll have no problem skimming it and just make sure the place is well ventilated. If the background is not wet , should be okay after a week , ten days to paint but it depends on the conditions. You can go up to 25-30mm before you should mechanically fix eml to the wall but I've seen more go on walls with no problems.

It's surprising the thicknesses you can build up with todays lightweight backing/undercoat gypsum plasters. As long as the first coat is onto a well keyed substrate, then no problems. As Micilin says though, let each coat set, and scratch well, before putting the next one on.

 

[stevegreen]

These blocks are very dry but they are concretes (oversight at start of build!) don't really mind waiting 3 weeks before painting. Is it possible to plaster hardwall onto sand and cement scratch used as a basecoat to acheive final thickness. i.e one coat of s & e and then one coat of hardwall (to satisfy BC) finished with skim.

 

[roughcaster]

These blocks are very dry but they are concretes (oversight at start of build!) don't really mind waiting 3 weeks before painting.

Is it possible to plaster hardwall onto sand and cement scratch used as a basecoat to acheive final thickness. i.e one coat of s & e and then one coat of hardwall (to satisfy BC) finished with skim.

Yes is the short answer,, no problem.
You can put ANY Gypsum undercoat plaster onto a sand and cement scratch coat,, but you should NEVER put any sand and cement mix onto a Gypsum plaster.