Tuesday, May 29, 2012

Why grout cracks in tile installations

The most visible part of any tile installation is, of course, the tile but what is the next thing you see. The grout! The grout, in many ways, is more visible as the smaller lines that make that up can draw your attention away from the tile itself. If those grout lines have cracks or are crumbling, your eye will naturally shoot right to it.

So let's look at few things and how they should be handled to make sure that the grout you use compliments your beautiful tile. Do you know the difference between sanded and unsanded grout and where each should be used? Now the difference in the two is easy. One has sand, one doesn't.

Applying grout

Now where to use which one is determined, not by the tile itself, but rather by the width of the joint between them. 

"Narrow joints of 1/8 inch or less call for unsanded grout, a pudding-smooth blend of Portland cement and powdered pigments mixed with water. Joints wider than 1/8 inch get sanded grout — the same material, but with sand added. The sand helps bulk up the grout and keeps it from shrinking in the joints." - ThisOldhouse.com

Now why does grout crack? You've applied the proper grout but down the road cracks start to appear in your grout lines and there can be many reasons but most have to do with the installation long before the grout was added. Most of what we will look at today is in reference to flooring but there are many points that are similar with all tile installations.

1. The first potential reason is that the thinset below the tile was improperly applied and does not have enough thinset.

Thinset application on floor

2. The subfloor is moving and as it moves the grout lines crack.  Did you apply the tile directly to the wooden subfloor? Tile should never be applied to a wooden subfloor due to the natural movement that is part of wood.

3. Was the cementious backer board that was applied over the subfloor installed correctly? Maybe there weren't enough screws or thinset below or it was spaced improperly. Any of these could cause movement and that causes cracks.

Cementious backer board installed

4. As another possibility- Is there adequate space between your wall or wooden trim and your grout? Grout doesn't contract and expand but wood does and that could be part of the issue too. It is a good idea to leave a 1/4" space between any tile and wooden baseboards or trim so that if the wood expands, it will not apply pressure to the tile and possible crack the grout. To accomplish this a "shoe" molding can be applied to the baseboard, effectively covering the gap and allowing the baseboard to move above the tile while applying no force to the tile or grout.

5. Did you apply your tile on a newly finished/poured concrete slab? Concrete has to cure and as it does it moves, so if your concrete floor or base is new and the tile was applied too soon, it could be the reason your grout is cracking. 
I would also add there could be other reasons for grout to crack other than those listed above such as improper mixing  ie too much water in the mix. This would cause the grout to improperly dry leaving it prone to cracking later.  It could also be that water was added again later in the mixing process and this will cause the grout to be dry and crumbly.

Now if you are still in the planning stage I would offer a suggestion or rather a product and installation method that will help avoid the problem of movement and grout cracks. It's a mat that is laid in a bed of thinset and then a layer of thinset is applied above with the tile and grout.

Schluter- Ditra-X for floor tile installation

Schluter-DITRA-X


What this mat does is provide a separation between the sub flooring material, whether that be wood or concrete so that if there is movement in the concrete/wooden sub floor, it will not translate up into the tile and grout and cause cracking.The mat will take the added stress of the movement below and not the tile/ grout therefore helping to eliminate cracking. For further reading about this product-http://www.schluter.com/Schluter-DITRA-XL.aspx 


As we have pointed out before, planning ahead and armed with knowledge will lead to a successful installation as it is so much easier to do right the first time than have to go back and correct later.



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