Expert: Jim Carlin,csi,csms - 2/2/2008

Question
We are planning to have porcelain tile installed on our screened in porch floor. We live on a crawl space. The porch is currently concrete. When it rains, we have standing water on one side of the porch that remains until it evaporates. We are planning on getting the V5 rated tile. The climate here is very hot and humid in the summer for 5 to 6 months. We rarely get snow. Temps in the winter occasionally get into the teens for a few nights a season. We often have bad thunderstorms and heavy rain. We also have 3 big dogs that run in and out of the house across this porch. Will this tile stand up to the standing water, the dogs, and the climate?

Answer
Hi Janet,
Based on the description of the front porch I have to say there is one major problem. The standing water is the clue. The slab needs to have a pitch or slope away from the house and provisions made for the water to completely drain off the surface. This is usually at ¼ inch per foot. Will the screen frames affect the water drainage?  How will you treat the screen door area? Are there steps to the porch?   
Porcelain tile is the perfect choice for exterior use since the temperatures run the full range including freezing. Porcelain alone is considered frost proof but how it is installed will affect how long it stays in place. Since water expands when frozen, the last thing you want is a puddle on the floor.
Correct the slope of the floor for drainage. Use an uncoupling membrane to accommodate the expansion and contraction caused by the temperature swings. Be sure and flash the slab to the building with the appropriate membrane and that there is enough height between the porch and the entrance door to hold back any water from a bad storm.
Janet I know it sounds like overkill, but think about what you are proposing to do and the damage that water can cause over a period of time. Look at Schluter.com for their systems for exterior decks.
Jim