Ceramic Tile Over Mastic

You can lay new ceramic tile right over the old using the prep techniques we show here.

Ceramic tile over mastic.

Tiling over an uneven surface will give you less than stellar results so level out any globs of dried grout with a sander and secure loose tiles with fresh tile adhesive before beginning the project. I think that s the right way to do this because i just start a job and i had to remove 2 tiles to continue the job and then i found they apply red guard over the existing concrete and basically was loose the red guard because i was breaking the tile hitting on the top and everything together was coming in the tile pieces tile thin set and the red guard so that s why i think with the primer. Roughen the tile with 80 grit sandpaper. Not recommended for tiles over 15 inches.

To replace a broken tile butter the back of a new tile with mastic and press it securely. Should the tile get wet the mastic may soften negatively affecting the bond of the tile to the substrate. It s available as a thin liquid thick glue or a sticky paste. Press the tile onto the floor.

I began using the 447 primer over the mastic and that helped some. Grind them down with a grinder. When the building was converted to residential the developer removed the vinyl tiles and just carpeted over the mastic. Liquid nails would be a notable example of the thin liquid form where it comes in a caulking tube and squeezed out along a wall or joists to hold load bearing walls and ceilings in place.

The adhesive often called carpet mastic used under most glue down carpet is usually water soluble and tends to prevent thinset from properly adhering. Lay a level on the old tile and mark any high spots. Does not fill gaps in a substrate or have building characteristics as it is more watery than thinset. Contractors we have spoken to think the best approach is to put down new ceramic or porcelain tiles right over the existing adhesive.

When i walk on what i have tiled sometimes i pop up a tile or a couple tiles but over most of the area i can walk fine. I don t want to go further till i know what i need to do to the mastic it s a very thin coat as if applied with a brush or roller it s not at all lumpy. They said capping the mastic in a seal coat or thin layer of concrete wouldn t be a good idea they d need to pour rather a lot of concrete for that. Mastic is an organic glue made from the sticky resin of the mastic tree.

Mastic adhesive is very sticky making it well suited for vertical applications where tile may slide. It avoids the time consuming messy tear out process.