How many of you have ever wanted to have a go at cement rendering a wall at home, or even creating a feature wall? Well my name is Christopher and I have been a solid plasterer now for about 40 years. First I will start by explaining to you what you will need to begin.
The materials you will need are basically sand and cement. The sand is called plastering sand, and don’t get it confused with what brick layer’s use. That sand is commonly called brickies loam, which is too fine for what we want it for. Plastering sand is courser than brickies loam and finer than river sand.
The standard mix is generally 3:1, which means 3 parts sand to 1 part cement, usually measured out by the shovel. Now the other ingredient you will need is a liquid that goes into the water mix to push air into the mix to make it more easy and spreadable to use.
Here in Australia we have a few product’s which do this. One is a clear liquid that does exactly what I’ve just explained. Usually you use I cap into the mix. Now a standard mix in a cement mixer is usually 9:3, 9 shovels of sand to 3 shovels of cement. And don’t forget to add 1 cap to the mix.
Also you can use detergent which gives you the same result.
So now we know what material we need to make up a batch of compo. Compo is short for composition, so this batch of your mix is composed of these 3 ingredient’s. Now the best way to mix these 3 ingredient’s together is in a cement mixer. Just put about 6 pint’s of water in the mixer and start adding the sand and cement bit by bit.
Usually 3 shovels of sand then 1 of cement and repeat this twice more. So now you have your batch of compo mixing in the cement mixer. You need the mix to be not too stiff and not too wet, a bit like when you make mashed potato, but a little bit stiffer. You see what we want is a mix that is easy to spread over the brick work and get it as flat as we can.
Now remember do not make the mix too wet as this weakens it. If you do make it too wet be sure to add more sand and cement to the mix to make it up to the 3:1 mix. If you throw in an extra shovel of sand, you have to throw in 1/3 of a shovel of cement. Now we can tip the mix out of the mixer and into a wheel barrow.
The tools that you need for applying the compo to the wall are a # 1. hawk, this is like a small flat board with a handle under it, we put our compo on this board and then with a trowel we trowel it on to the wall we are rendering. #2. As just mentioned we also need a trowel #3 we need a float usually made of timber with a flat side, this is what we use to float the wall up to a flat finish.
#4. we need a sponge, now you can buy these from any trade center or even hardware stores. It looks like a float but it has sponge stuck to the base plate and this is what we use after we have floated the wall up to achieve a flat sandy surface. #5 you will also need a straight edge to rule the wall off. Years ago the straight edge was made out of timber and still are, but I use a metal straight edge now.
So now we can start laying on the wall we are going to render. Usually if you are right hand you start from the right and go to the left. Opposite if your left hand. Lay the compo on to the wall with an even thickness, and try to get it as flat as possible. This will help when you start the finishing stage. So once all the wall is covered with our compo, we use the straight edge to gently rule the wall off and making it flat and straight.
The area of the wall the straight edge does not touch, is called a slack and has to be filled in again. Then with the straight edge you rule off the slacks on the wall to get a flat surface. Now that the wall has been ruled off it is now ready to float the wall up. Gently start with the float rubbing the wall up. You will see what I mean when you start using the float on the wall, that it will pull the sand and cement all together and it will fill in any holes and blemish.
If the wall has gone a bit dry when you start floating, just throw a little water on to the wall with a brush. This will bring life back into the compo so you can finish floating your wall up. Some times the brick work you are rendering will suck all the moisture out of the compo, hence you need that brush to continually wet the surface while you are floating. You will get the feel of the wall as you continue. If the wall is going off (a term used when its drying too quick) then you
will have to sponge the wall as you go. Sponge the wall in a circular motion until all scratch marks have disappeared. Continue doing this to the whole wall until you have a flat sandy surface. This is the finish that we want.
Don’t be alarmed if your wall is going off too quickly, like I said that brush of water will bring it back. Just do a section at a time starting again from where you first started laying on the wall. Now regards painting cement render you are supposed to wait 28 days for the cement to cure but there are primers available to use on render that is 3 days old. Just talk to your paint shop and they will tell you what is available.
So I hope this article is helpful to you if you decide to try cement rendering a wall at your house, and remember just take your time and go step by step as I have explained and you will finish that wall.