Render Consistency.

[K-Rod]

Hi everyone,

I plan to render a breezeblock wall shortly, it's my first attempt but I've done a little bit of plastering before so hopefully I'll be ok.

I was just wondering what consistency the scratch coat and top coats should be. Should they be like mortar or more like plaster? i.e. a bit runnier.

Any help and guidance is appreciated as always.

K-Rod.

 

[roughcaster]

Cement render should be as you said, "the consistency of mortar", which is what it is,,,,, mortar. A good render scratch coat/top coat should be mixed up in a mixer for the best results. A shovel full/trowel full of well mixed, aerated mortar should "stand up" and not fall off of the shovel or the trowel,,,,,, if you know what I mean. The sand should be plastering sand (soft) not sharp.... 4 of sand.. to.. 1 of cement is a good mix for a scratch coat, and a waterproofer/plasticiser should be added to the water. Evo-Plast is the one I use. Around £15 for 5 litres. Mixing ratio: 30 parts water to 1 (one) part Evo-Plast, which I measure out "exactly" into my water barrel, and give a good stir up. There are other brands available but I like the simplicity of the ratio with this one. The more the mortar is allowed to mix with the plast'r/waterp'r., the less water you will need because it becomes aerated, but never overmix it. Also,too much water added to the mix makes a batch "heavy" and liable to slumping. The top finish coat of render would normally be 5 of sand.. 1 of cement.. and 1 of lime, (optional) and mixed up in the same way. Put some water in the mixer first, but watch out for splashes in the eyes as you add the sand and cement to the water.... I like to measure the sand and cement used in each batch, with a bucket, but you can judge it, with a little experience by using a shovel, also, I like to keep the pile of sand covered from the rain if possible. If the sand is too wet from the weather, it'll affect the amount of water you use with the plasticiser/waterproofer in from the water barrel, and you wont get such a good light, buttery, mix....... I think you have a good idea of what you're looking for, but there's a few tips above that might be of some use to you, if you need them.

Roughcaster.

 

[K-Rod]

thanks roughcaster, excellent advice.