DIY help needed, (cement based plaster)

I know this is a bit random, but someone somewhere must know how to mix cement based plaster, for preparing my walls before appling smooth plastering, I know how to plaster but only from pre rendered walls and so need to know how to mix the cement plaster to render my walls. i have been told that it is 6 parts sand to one part cement, but surely this needs some plastersiser (sp?) or something?

Someone somewhere must know something have tried google but only tells me to buy ready mixed which is too expensive and I already have a tonne of sand and 40 bags of cement at my disposal (building back wall)

thanks for looking even if you cant help

Your mix ratio sounds about right for a scratch coat Donna.Adding a plasteciser like 'Feb' does have the benefit of making the mortar mix more usable and stops it going off too quickly.You may want to consider brushing a PVA mix onto the brickwork first though cause then you'll guarantee the mortar will stick.

If you can get hold of one-use a paddle to mix the cement with an electric drill cause they take all the lumps out.

Thanks Steve, I was beginning to panic, just removed all the old plaster from the wall to find that the 'scratch coat' is crumbling (and shot/blown?) and also needs to come off, really should have expected it as the house is nearly 100 years old and the lady who lived here before lived here 75 years and according to her brother it was never replastered. what is the ratio of plasterciser do you know? Sorry just took a short course on top coat plastering, dont know anything about the 'scratch coat'

The scratch coat is called this Donna cause when you apply it-you literally scratch lines all over it about 1/2hr after you finish.Easiest way is to hammer 6 nails through a scrap piece of timber and drag this across the mortar.Its done so the final coat of plaster has something really grippy to adhere to.

You dont need much plasteciser-i would use about 3-4 cap fulls in a cement mixer load so if your mixing up a bucket at a time-not a lot! Beg,borrow or steal a little cause i doubt you will ever use it again!

You say the house is old and the old mortar was dropping off-make sure you give the brickwork a damn good clean with a soft brush to remove dust.I cant stress the importance of brushing a PVA solution first onto old brickwork to ensure the scratchcoat stays stuck on!

Thanks again steve, luckily we have loads of plasterciser because of the brick wall being built around our back garden