The bathroom topping mortar to get falls on the floor, the bedding of the bath itself (previous page) and odd plastering and patching of the walls prior to tiling bathroom all used the mixing setup shown here.
|Bathroom topping mortar – My mixing set up|
In addition to the mortar mixing, the same mixer and drums are used to mix the ceramic tile adhesive which come pre-packaged in bags that only needs the addition of water. This can be mixed by hand but the large drill and mixer is a lot more efficient with less chance of getting lumpy results.
|Bathroom topping mortar – Large slow speed electric drill with mixer|
So to mix the mortar here is what I used.
- Fresh washed brickie’s sand.
- Fresh bags of standard Portland cement. I don’t mind using old part bags of cement for odd jobs, but I always like fresh stuff when doing a job like this.
- A shovel, a couple of trowels and a plaster’s rectangular float.
- Home made plaster’s hawk. A square piece of 3mm aluminium with a handle on the bottom.
- My large slow speed drill with big mixer in it.
- A couple of 20 liter metal drums for mixing the mud in.
- A larger garbage drum full of water for washing the mixer in after each mix. That is, when the mixing has been done, the mud left on the tool is washed off by sticking in into the garbage drum and the drill is run at a higher speed to clean the mixer.
- A 4 liter tin of “Bondcrete”. A PVA type of cement additive that improves adhesion, water resistance and strength of thin layers of concrete and cement render. There are many similar products.
- Not shown in the photo is a couple of large sponges, the type you use for washing cars.
- I have quite a few different length screeds handy. They are straight lengths of box section aluminium that I have collected over a period of time for straightedges etc. A couple of straight pieces of timber would be OK. Anything straight and easy to clean is OK.
- I also have a sieve that I can use if the sand gets lumps in it. If you have lumps of stone etc in the sand it is a real pain. It is easier to sieve the sand first than pick them out of the mud later.
Cement Additive, PVA Type, “Bondcrete”, “Lokcrete” Etc.
I always use the PVA “Bondcrete” type additive for this sort of work. Read the instructions on the tin. It is a thick milky white liquid that could be just about the same as PVA wood glue to look at.
I used Bondcrete years ago to do a wheelchair ramp, and I explained to the owner at the time that the correct and best way of doing the job was to cut out a section of the old concrete, so that the new concrete ramp had a minimum thickness of 50-75mm or so.
I then said we could try laying a mortar mix down to almost a feather edge, 5mm or so, using Bondcrete, which would be a lot cheaper, but no guarantee that the thin edge would not spall away in time. I went back to do more work there a few years later, and it was still as good as ever.
- I get a section of wall ready by sweeping off the loose dust and then I wet it down with water, if the wall is very dry and porous it will soak up the moisture in the plaster too quickly and compromise the bond.
- In one of my buckets I mix Bondcrete 1 to 10 (or a little bit thinner) with clean water to make my mixing water. This water mixture made up beforehand makes sure that the cement render has Bondcrete evenly mixed into it.
- I prime the prepared wall section with Bondcrete diluted at say 4 or 6 to 1 with water. The idea is to paint or roll this primer onto the surface that will receive the plaster. The new plaster should be applied while the Bondcrete primer is still tacky. If it dries completely prime it again. Not being an expert, for this reason I prefer to only do a small section at a time.
- I put my mixing liquid (water and Bondcrete) into my mixing drum and add cement, and give it a quick stir, then add the sand. The ratio is about 4 to 1, sand to cement.
- I only make up enough, say half a bucket, that is easy to carry inside and easy to get onto the wall. If I made up a wheelbarrow full I might not get it all used before it starts stiffening up.
- Don’t mix up too much, until you get a feel for the material and how long it takes to go off. It is quite different from plane sand and cement.
- This cement render with the additive in it is good stuff, and consequently sticks like you know what, to your tools, the floor and anywhere else you might splatter it. Allow yourself time to clean up well.
- A main fault of home plaster and concrete work in general is that because the work is hard and physically tiring, when the plaster is on the wall or the concrete screeded off, people relax, have a rest, maybe a beer or two and forget about the clean up.
- I am not an expert plasterer by any means, so what I do is get it onto the wall as good as I can with the steel float, (rectangular steel trowel) not playing about with it at all, then when it has had a bit of time to stiffen I use a screed to level it a bit better.
- Where a tradie plasterer will then finish it perfectly, I like to leave it a lot longer, and then scrape the almost hard plaster flat with the edge of a screed.
- Any bits that fall off, or hollows, I patch up in a second session.