How To Apply A Self Leveling Compound To A Plywood Sub Floor
Floor Leveling Tips
By Troy Cantini
It is critical to get your sub floor as level as possible before installing tiles on it. Installing tiles on an uneven floor can cause lippage in the tiles. Also if the floor gets wet then water can pool up in the low spots. It is best to have the sub floor as level as possible before installing any type of flooring product on it.
A self leveling compound can be applied to most types of subfloor materials. You can apply self leveling compound to plywood, osb, concrete, cement board, hardibacker and many other types of subfloor materials. You can also use self leveling compounds when installing tile over top of an existing tile installation. Self leveling compounds will not add any stability to a sub floor that is flexing or shifting. It is important to totally stabilize the subfloor before applying the self leveling compound.
Stabilizing a subfloor may involve adding more floor joists or sistering the existing floor joists. Also a second thicker layer of a wooden subfloor will also help to stabilize a flexing subfloor. If you apply the self leveling compound to a floor that is flexing then it will crack and shift as the floor is being walked on. Also the tile and grout will start to crack as well if they are installed on top of this type of flexing subfloor. If you can walk on the existing subfloor and notice that it is flexing or moving up and down while you are walking on it then you need to stabilize the sub floor before applying the self leveling compound.
The preparation of the sub floor will be different depending on the type of sub floor you want to level. It is important for the self leveling compound to properly bond with the subfloor so preparation is the key. You can apply self leveling compound directly to hardibacker, cement board or any other approved tile setting materials. If you are applying the self leveling compound to a concrete floor then it is important for the concrete floor to be totally clean and free of dirt and debris. When applying a self leveling compound to an existing tile installation it is important that the tiles be sanded down and scuffed up so that the self leveling compound will bond with the existing tiles.
You should not apply the self leveling compound directly to osb, plywood or any other types of wood based material flooring materials. For wood based sub floors you must first apply a bonding agent to the subfloor to get good adhesion with the self leveling compound material. Applying a metal lath with staples to the wooden subfloor will also work to properly adhere the self leveling compound with the wood based subfloor. You should read and follow the instructions closely as to what bonding agent is recommended for the particular brand of self leveling compound you are using.
When initially poured the self leveling compound will be extremely runny and have the consistency of pea soup. It is important to caulk around all the edges and seams prior to applying the self leveling compound. You do not want the self leveling compound dripping out or down below especially if you are applying it to a second floor room. You should also tape up any vertical finished beams or walls so you do not mess up the finish of these areas while applying the self leveling compound material.
Applying self leveling compound to a single room is a fairly straight forward process. You should first know the height that you want your subfloor to be mark this area off. It is important that the new height of the subfloor is higher than any of the existing high spots in the floor. The easiest way to line off your room is to use a revolving laser level and set it on the highest point in the room. Then you can draw a line around the room where you want the new subfloor height to be. You should read the self leveling compound instructions completely to know how much of the self leveling compound material you are going to need to level your floor to the desired level.
For large rooms or multiple areas you can not just pour the self leveling compound in one area and expect it to level out. You should have all of the self leveling product mixed and ready in buckets before you start the job. For larger rooms where a large amount of buckets of the self leveling compound are needed a helper is recommended to mix the self leveling compound while another person pours it.
You should always start in the farthest away area from the door and pour the self leveling compound out till it reaches the desired height. Then you can slowly keep pouring buckets of the self leveling compound in the room till you walk out the door. In larger rooms a professional self leveling roller applicator is needed to gently move the self leveling compound so that all of the areas of the floor get good even coverage and the floor will be totally leveled.
Applying self leveling compound in larger areas or throughout multiple rooms will require a system of mixing, carrying and leveling of the self leveling compound. A team of contractors or helpers will be needed because it is impossible to mix enough of the self leveling compound mixture beforehand. You do not want the self leveling compound to set in multiple buckets before you start pouring it out on the floor. You also will not be able to mix and pour at the same time because the self leveling compound mixture will start to set up and you will not be able to accurately pour it throughout the house.
It is best to have at least one person dedicated to mixing the self leveling compound while another person will carry the self leveling compound mixture. A third most experienced person will then use the self leveling compound roller applicator to ensure that the floor is being accurately leveled with the self leveling compound. For extremely large areas it may be necessary to have multiple individuals dedicated to mixing so that they can keep up with the self leveling application time frame. In larger areas special spiked shoe attachments work well to allow you to walk on the poured self leveling compound without disturbing its natural leveling characteristics.
After you have poured the self leveling compound and got it to be at the level you want it then you can generally start applying tile or other types of flooring materials the next day. You should always read and follow the manufactures instructions closely as to how long the self leveling compound needs to set. You may have to wait longer when installing carpet or hardwood floors to ensure a totally dry environment in the subfloor before installing these types of flooring materials.
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