Gypsum Plaster versus Plastering Sand and Cement

[Ambergreen45]

Hi,

My internal walls are plastered with sand and cement. Some patches are a bit loose so I want to re-plaster those areas. Are there any advantages for using gypsum plaster such as Hardwall as a base coat, though it's more expensive than using a weak mixture of plastering sand and cement?

If using gypsum as a base, could I soak the porous brickwork or is PVA a must?

I've got almost a full bag of gypsum multifinish 2 months over it's sell by date. It's wrapped into several plastic begs to make it airtight and have been kept indoors. It still should be ok to use, shouldn't it? Or what is likely to happen?

Thank you.

 

[NickB_99]

I've got almost a full bag of gypsum multifinish 2 months over it's sell by date. It's wrapped into several plastic begs to make it airtight and have been kept indoors. It still should be ok to use, shouldn't it? Or what is likely to happen?

Thank you.

Wouldn't risk it if it was me.
It may go hard very quickly - sometimes whilst still mixing. Or may not set at all. The fact it had been opened, will make it worse.
It's a lot of work to put on and even more to take off and do properly if it does go pear shaped.

 

[ree]

The S&C render could have been used for a specific purpose - patch up with the same.

PVA is a great aid or help but its not essential, spreads got along for centuries until recent years without using PVA. Simply use your wet brush to take up the suction, and then immediately go to it with a scratch on.

As above with use by dated powder- DONT.