Can I Lay Tile Over Rough & Broken Outside Concrete?

Cracks

• A normal part of concrete is the fact that it cracks over time. During the curing process, the material shrinks as the water is absorbed into the concrete, plus cement naturally wants to expand during the warmer months and contract during the winter months. This leaves behind hairline fractures, but in some cases it can actually break the concrete slab in two. This is the reason expansion joints are included in slabs -- to help prevent the concrete from actually breaking.

Expansion Joints

• If you want to install ceramic tile on top of a concrete slab, you have to include expansion joints. Because concrete will continue to move over the course of its life, this movement will naturally transfer up into the tile installation, leading to tiles popping off the floor and grout joints cracking out. Expansion joints need to be included every 25 to 30 feet for tile installations, and they should be no less than a quarter-inch in width.

Crumbling Sections

• If the concrete is crumbling in sections, it means the mixture wasn’t completely mixed properly during the initial installation. Instead, portions of the finished concrete have too much or too little water compared with the other elements. These sections need to be removed and completely cleaned of debris and dust so you can patch the slab and prepare it for tile.

Patch Coat

• Once all of the broken areas are cleaned and ready to patch, you can mix up a slurry mixture as well as some new concrete. The slurry mixture is pure cement and water that is mixed into a paintable consistency that is applied to the slab. While it is still wet, you then apply the concrete mix (of which cement is a raw ingredient) to flatten the slab and patch the broken area to prepare it for tile.