How smart waterproofing elevates your outdoor tile project

By Jesse Sanchez.

A trendy outdoor upgrade could lead to serious water damage without one crucial step.

Outdoor living is getting a makeover. From rooftop patios to tiled balconies, homeowners are reimagining unused spaces as stylish, functional retreats. But while adding tile or stone to a balcony or deck might elevate the aesthetics, MFM Building Products knows skipping one critical detail — waterproofing — can lead to costly headaches down the line.

Whether it’s a concrete slab above a garage or a wooden balcony off the master suite, tile installations exposed to the elements face a constant threat: water infiltration. Without a reliable barrier, moisture can seep into the substrate, causing mold, rot and structural damage over time.

Waterproofing is not optional — it's essential, which is something stressed by MFM Building Products, an Ohio-based manufacturer specializing in waterproofing solutions. Their product, SubSeal™, is designed specifically for these high-moisture, tile-over-structure applications.

SubSeal is a self-adhering membrane that bonds directly to concrete or primed wood substrates. It requires no mechanical fasteners or adhesives, making installation straightforward. The top layer is engineered to withstand the demands of tile or masonry mortars, while its flexibility allows it to move with the structure during temperature changes or settling.

What sets SubSeal apart, beyond its ICC-ES AC38 compliance and 10-year limited warranty, is its adaptability. It can be applied vertically or horizontally and works seamlessly with tile backer boards. For best results, installers should maintain a positive slope to drain, overlap seams by at least three inches and caulk tile edges using approved materials.

Professionals recommend securing the membrane with a termination bar fastened every eight inches on center and overlapping courses to guide water flow away from seams — not into them.

MFM offers detailed technical sheets, installation guides and even free samples through their website. As tile deck and balcony projects grow in popularity, don’t invite water damage — make sure the critical step of waterproofing is done right.

Learn more about why it's crucial to ensure what's beneath your tile can withstand the elements — before you break out the torch lights and deck chairs.