Self Levelling Compounds
Smoothing out and preparing a floor for tiling
Self Levelling Compounds (SLC) are used for smoothing and preparing a floor surface prior to applying a final covering such as ceramic, stone, porcelain tiles but also many other coverings.
The slc is not designed to be used as a final surface to be walked onto as the material will not withstand the wear and tear of foot traffic and can be applied from a feather edge to up to 20 mm thick with the addition of aggregate/granite chippings. Some levelling compounds are suitable for outdoor use and others for internal only.
There are different types of slc and these have their particular use on different situations, more manufactures are developing their specialised brand type. I have used two different type of slcs:
Water-Based self levelling compound.
Acrylic-Based self levelling compound.
The water-based SLC is a single part compound that is mixed with a specific amount of cold and clean water; this amount of water can be slightly adjusted depending on the air temperature and surface's absorption.
The acrylic-based is a two parts compound that has to be mixed with the corresponding liquid polymer.
The open work and drying times are dependant on many factors but slow curing and setting are easier to handle than the fast setting types. Always read the full instructions and guidance that is usually found on the back of the product. Protective clothing is a must and that includes a well suited face mask, as slcs produce lots of dust when mixed and could cause respiratory complication.
Although the products are known as "self levelling" it is not quite the same in practice and smoothing compound is a more appropriate name.
For the first timer and even for some hardened D.I.Y. er, the application of such product can be quite a challenge and the best way to go about it is to mix a small amount first and use it in a test area. Get to know the "beast" before carrying out a medium to large job.
There are different ways to smooth floors by using slcs and can be applied by pouring by bucket or by pump. The latter is more appropriate on very large floors.
So, what tools do you need for small areas you may ask? Here is a list:
- clean buckets (1 for mixing, 1 for the water, 1 for cleaning spillage's)
- mixing trowel
- metal float (plastering)
- 6 mm notched trowel (for even spreading)
- power drill with mixing paddle or industrial adhesive mixer
- Tip: spiked shoes if in need to walk over S.L.C. while smoothing - these are also used for aerating lawns
- dust sheets (for protection of access area)
- face mask
- latex or rubber gloves
When mixed with water, you must achieve an optimal consistency as if you put too much water, the slc will be too weak, also it won't spread well as the heavier particles (sand) will fall at the bottom and the watery part will escape before you have the time to say... "bother". :) If on the other hand the mix is too hard, then it won't self spread (unless you have so much that you can swim in it. :)
Another thing to remember, is that the slc can find its way through small cracks and gaps, so make sure to seal all these areas before you start pouring it down.
You can make it easier for yourself if you have a spiked roller and an adjustable professional spreader
The roller is for getting rid of air trapped in. It will help slightly on spreading the compound.
Using the adjustable spreader make life a lot easier as you can stand up and use it like a broom, you will also see great improvements and because you use it standing up, it makes the job quicker and saves your knees.
You can adjust the height required and because it has several pins it will even up bad areas better than your tile spreader would. They come in different widths but 80 cm is great for medium domestic jobs.
A word of caution when used on u/f heating wires as you could damage the wires with this tool. Also caution when using rollers as you can "spray" the adjacent walls and furniture with levelling compound. Always move it extra slow and parallel to the object/wall/doors...
The best way to deal with levelling compound is to find out how much and where you need it. My approach is like this:
- 1) Place a cross laser level on a pole, spreading the laser horizontally from one corner of the room towards the opposite corner at a height of approximately 1.1m.
- 2) Get a 1.2 m spirit level and stand it in front of the laser beam.
- 3) Making sure that the spirit level is "Plumb", make a mark where the laser shows on the spirit level.
- 4) from then on I can cross reference that mark on the spirit level across dozens of places to see how good/ bad the floor is.
You can also stick some broken tiles with appropriate adhesive or sand and cement (according the height) as reference points so you know how much it needs raising.
Hope this is useful information to some of you.