Self-leveling concrete thickness

How thick can you pour self leveling concrete?

Self leveling concrete thickness depends on the product, so here are the published limits for some widely sold underlayments. "Neat" means mixed with water only; "extended" means with ⅜ in pea gravel added. Read them as what the category can do, then check the bag you actually buy.

So the self leveling compound max thickness, neat, is 1¼ to 2 in, and the bag's figure is the one that counts: a floor with a 1½ in dip is one neat pour with one product and a gravel fill with another.

How thin can you pour self leveling concrete?

The self leveling concrete minimum thickness for most underlayments is ⅛ in at the highest point. Thinner than that, the layer dries before it bonds and can powder or crack under flooring. A few products are sold to feather to zero at the edges; if the high spots of your floor need nothing at all, that is the kind to buy, or the high spots get ground down first.

That is also why depth is planned from the high point. Find it with a long straightedge or a laser, decide the leveler has to be ⅛ in there, and every other spot on the floor is ⅛ in plus however far it sits below. A floor that is ¾ in out across the room is not a ¾ in pour — it is ⅛ in at one side and ⅞ in at the other.

How thick should self leveling concrete be?

As thin as the floor allows: ⅛ in at the high point over concrete, ⅜ to ½ in over wood, and no deeper anywhere than the dip needs. A thicker pour is not stronger in any way that matters under flooring — it only costs more bags and more drying time.

How deep can you pour self leveling concrete with gravel?

Past the neat maximum the mix is extended with clean, washed ⅜ in pea gravel. Sika's rule is typical: gravel no more than a third of the total depth, spread on the primed floor and flooded with leveler, then a final ⅛ to ¼ in of neat mix on top so the surface is smooth. Extended, the products in the table reach 2 to 5 in.

The other route is two lifts: pour to the bag's maximum, let it cure, prime again and pour the rest. It costs a day, and is usually the better choice for a deep dip in a small area, where shoveling gravel is more trouble than it saves.

Bags of self leveler by thickness

A 50 lb bag mixes to about 0.45 cubic feet, and covers that volume spread at your depth. Halve the depth and it covers twice the floor.

Bags are rounded up to whole bags, as the store sells them, for a flat pour at that depth. A real floor is a slope from the high point to the dip, so the average depth is what sets the count — and you will want 10 % on top for what stays in the bucket and the pump. The self leveler calculator works that out from your own high point and dip.

Thickness over plywood and wood subfloors

Wood moves and concrete over it cracks, so pours over plywood come with more rules: a stiff subfloor, the maker's primer, and a reinforcement fastened down so the leveler has something to grip — usually expanded metal lath, though some makers specify their own mesh or mat. The minimum depth over wood is then set by burying that reinforcement: typically ⅜ to ½ in, and more where the joists are spaced wider than 16 in. It is never the ⅛ in that works over concrete. Some products are approved over wood only under flexible floors such as vinyl and carpet, not tile.

Whatever goes on top decides how flat you need to be. Laminate and click vinyl usually ask for 3/16 in over 10 ft; large-format tile asks for ⅛ in over 10 ft. The laminate flooring thickness guide covers what the floor itself adds on top.

The self leveler calculator takes the room and the depth at the high point and in the dip, and gives the bags, the primer and the water.

Figures: thickness ranges from the manufacturers' published data for the products named; bag yield 0.45 ft³ per 50 lb bag, the middle of the 0.42–0.50 ft³ range printed on common bags. Limits differ between products and between substrates — the technical data sheet for your bag is the one that applies.