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Last Updated: , Created: Saturday, January 10th, 2004

Self Levelling Concrete

Kim from Victoria, B.C. pulled up a carpet and discovered that the concrete floor slab was not level with the door sill. What to do? Use Self Levelling concrete.

This is an easy to find but very special type of concrete that will say 'Self-Levelling' right on the bag. It is designed to flow like water, hence level itself, but set hard like concrete. Although great for levelling floors, its thin consistency means that it is not as strong as regular concrete and you cannot use this outdoors or where it will not be covered by something else. But this is the product of choice for levelling out sub-floors. For a very large floor you may want to check the price before proceeding because building a level sub-floor could be less expensive when you need a lot of it.

First you put a specific primer, bought where you bought the concrete, onto the floor to help the concrete to stick well.

Second, you caulk or stuff up any cracks and build a barrier around the edges of the area you want to work with. This stuff is so thin that it will flow down a crack and all disappear below. You can put this over an old hardwood floor to level it out, but you have to seal between the boards first, or it will all just drip down to the ceiling below! The floor must have no movement in it or the concrete will end up cracking. Remember this has no strength of its own, but it makes a good hard sub-surface for other finishes from carpets to floating floors.

Third, and critical, is that you mix it exactly like it says on the bag. Everyone wants to add more power to the mix because you are sure it will never set-up. Follow the instructions exactly. Yes it is thinner than pancake mix; as thin as a French crepe mix.

You only have 15 minutes to work with it so don't mix up any more than you are ready to pour immediately. You can work with it in multiple layers.

Pour it out. You may want to help smooth the feather edges, but do that quickly. Actually what you are doing is simply wetting the floor on the outer edge of the pour so that it can flow smoothly to its own level. Let it set at least 3 hours before walking on it. Wait several days for it to be completely dry before covering it with anything that will block evaporation. Remember, all that water needs to get out.

Click here for a through discussion about Myths and misconceptions about concrete and water.

Keywords: Floors, Types, Concrete, Levels, Repair, Sub-Floor, Techniques

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