Deck Waterproofing — Protect Your Investment from Georgia Rain

A full membrane system typically costs $15-$35 per square foot installed over a plywood substrate. For a standard 300 sq ft second-story deck, that's $4,500-$10,500 including materials and labor. Simpler waterproofing — like sealant application on wood framing and proper ledger flashing — costs significantly less. Under-deck drainage panel systems fall in the $8-$15 per square foot range. We provide free estimates with exact pricing.

A waterproof deck membrane is a vinyl or PVC sheet that gets installed over a plywood substrate on your deck surface. It creates a completely watertight surface that looks and feels like a finished floor — textured for traction, available in multiple colors, and UV-stable. Water runs across the membrane surface and drains off the edges into gutters or downspouts instead of seeping through the deck boards. It's the best solution for second-story decks with living space below.

Nine times out of ten, deck leaks at the house wall are caused by improper or missing flashing at the ledger board — the horizontal board that attaches your deck to your house. Water gets behind the siding, wicks into the house framing, and causes rot. We see this constantly on older decks. The fix involves removing the siding at the connection point, installing proper metal flashing and self-adhering waterproof membrane, and reattaching everything correctly. It's critical work that prevents major structural damage.

Yes, but it depends on the deck's current condition. For membrane systems, we need a solid plywood substrate — if your existing deck has gaps between boards (like standard deck boards), we'll need to install plywood over the framing first. For under-deck drainage systems, we install panels between the joists under the existing deck without disturbing the deck surface at all. We assess your specific situation during the free estimate and recommend the best approach.

Composite deck boards themselves are highly water-resistant — they won't rot or absorb moisture. But the framing underneath is still typically pressure-treated wood, and the space below the deck still gets wet when it rains. If you have living space under your composite deck, you'll still want an under-deck drainage system to keep that area dry. Proper ledger board flashing is critical regardless of what deck surface material you use.