QUESTION

Do I need Expansion Joints? and Crack Isolation Membranes? - I have an exterior patio on ground that is and has no expansion joints, and has several cracks. What is your recommendation for the cracks or the type of barrier to be applied.

ANSWER

ANSWER - Per TCNA EJ171 standard, exterior tile applications should have expansion joints (movement joints) every 8 to 12 feet in all directs and be filled with a backer rod or tape and a C920 sealant (structural silicone or urethane).  If there are expansion joints in the patio concrete slab then they need to continue up through the tile.  If there are no expansion joints in the patio slab then the generic expansion joints should be placed within the tile assembly in an area where there is a grout joint, so it will not visually stand out.  The tiles cannot be butted up tightly to restraining surfaces (walls), but should have at movement joint at those transitions.

If the concrete patio substrate has cracks then first you have to determine if they are a structural crack (has lippage indicating it has moved vertically) or a shrinkage crack (only moves horizontally within the same plane).   If they are structural cracks then they have to be professionally repaired with epoxy and dowels.  If they are shrinkage cracks then you can apply a crack isolation membrane over the whole slab for full protection or apply it only over the cracks so it is centered over the crack bridging it the width of 3 tiles you are using (e.g. 12x12 inch tile would require a 36" application of the membrane to bridge the shrinkage cracks).  Most crack isolation membranes are also waterproof membranes so you will also get the benefit of creating a moisture barrier to minimize efflorescence and other potential moisture problems.  Be sure to follow the membrane manufacturers' limitations and installation guidelines to be sure it is appropriate for the application and will perform as intended.  Good Luck.