ALX Westcoat
Deck Waterproofing
Under-Tile Membrane System — Class A Fire Rated · IAPMO ER-587
Greg Kaiser installs the Westcoat ALX system — the professional-grade metal lath reinforced waterproofing underlayment for plywood decks receiving tile, stone, or concrete. This is the system specified in commercial and Class A fire-rated construction. Not the stuff from Home Depot.
Materials: Westcoat Professional Systems ↗1What Is the ALX Westcoat System?
The ALX system is Westcoat's metal lath reinforced waterproofing underlayment — engineered specifically for plywood decks that will receive tile, stone, or concrete. It uses a WP-40 Sheet Membrane as a backup waterproof layer, then metal lath reinforcement over plywood seams and stress points. The result is a deck substrate that's waterproof at the structural level, not just at the surface.
- WP-40 Sheet Membrane — backup waterproofing at plywood seams and transition points
- Metal lath reinforcement — ties the system together across the deck surface
- IAPMO Evaluated ER-587 — independently certified system performance
- Meets AC-39 standards for walking decks — the code baseline for occupied deck surfaces
- Class A Fire Rating over concrete — meets commercial and residential fire codes
- Excellent sound reduction — reduces impact noise transmission to structure below
- Environmentally safe acrylic chemistry — no harsh solvents
- Flexible and durable — accommodates deck movement without membrane failure
2Deck Repair + Waterproofing Combined
Most deck waterproofing calls start with a failure — cracked tile, bubbling membrane, water showing up on the ceiling below. Greg's process addresses the root cause, not just the symptom. We demo the failed surface, inspect and repair any damaged plywood, then install the ALX system from the substrate up. You end up with a properly waterproofed deck that will last decades.
- Demo and debris removal — full surface prep before any waterproofing
- Plywood inspection and structural repair where needed
- WP-40 membrane at all seams, penetrations, and transitions
- Metal lath over the full deck field for reinforcement
- Tile, stone, or overlay installed over the completed system
- Flashing and edge details — where most failures start
Real Deck Repair Projects
3Why Greg Uses Westcoat — Not Generic Products
The deck waterproofing market is full of products that look the same but perform very differently. Greg Kaiser uses Westcoat exclusively because it's the same professional-grade system specified in commercial construction, HOA projects, and Class A fire-rated buildings. The IAPMO ER-587 certification isn't marketing — it means an independent evaluation body has tested the system and confirmed it performs to specification.
Serving All of Arizona
DnD installs the ALX Westcoat system throughout Phoenix metro, Tucson, Flagstaff, Prescott, Sedona, Cottonwood, and statewide. Whether you have a second-story deck over living space, a poolside surface, or a rooftop deck — we come to you.
Why Arizona Trusts DnD
Get Your Free Deck Waterproofing Estimate
We assess your deck, identify the failure points, and give you a straight quote. No pressure.
The DnD Quality Guarantee Package
Every DnD estimate comes with this — no catch, no obligation:
- ✅Free floor assessment & measurement$200 value
- ✅Family-Owned Satisfaction Guarantee — if you're not 100% happy, we make it rightGreg's name is on every job
- ✅Greg personally inspects every install before we call it done
- ✅Full prep process documented — you see exactly what we did and why
Deck Waterproofing FAQs
Real questions about the ALX Westcoat system — answered straight.
Q.What is the ALX Westcoat system and why does DnD use it?
The ALX system is Westcoat's metal lath reinforced waterproofing underlayment for plywood decks receiving tile, stone, or concrete topping. It's IAPMO evaluated (ER-587), meets AC-39 standards for walking decks, and carries a Class A fire rating over concrete. Greg Kaiser uses Westcoat exclusively because it's the same professional-grade system specified in commercial and Class A fire-rated construction — not the consumer products from a big-box store.
Q.What does "under-tile deck waterproofing" mean?
Traditional deck waterproofing sits on top of the tile. Under-tile waterproofing — like the ALX system — installs the waterproof membrane underneath the tile before it's set. This means the waterproofing protects the plywood substrate itself, not just the surface. When grout or tile eventually cracks (and it will), water can't reach the deck structure.
Q.Can this system be used for deck repair on an existing deck?
Yes — deck repair is a significant part of what Greg does with the ALX system. We remove the failed tile or coating, address any plywood damage, install the WP-40 Sheet Membrane as a backup layer, apply the metal lath reinforcement at seams and stress points, and then reinstall the tile or overlay. The result is a waterproofed deck that's engineered to last.
Q.What is the WP-40 Sheet Membrane?
WP-40 is Westcoat's sheet membrane — a secondary waterproof backup layer installed under the metal lath reinforcement in the ALX system. It's specifically applied at plywood seams and transition points where movement stress concentrates. Think of it as belt-and-suspenders: the lath handles reinforcement, the WP-40 handles the secondary waterproofing at the most vulnerable points.
Q.Does this system reduce noise from foot traffic on the deck?
Yes — the ALX system includes excellent sound reduction as a design feature. The metal lath and membrane assembly dampens impact transmission between the deck surface and the structure below. This is a significant benefit for second-story decks over living spaces.
Q.How long does deck waterproofing installation take?
Most residential deck projects take 2–4 days depending on deck size, condition, and whether tile is included. Day 1 is typically demo and substrate inspection. Day 2 is membrane installation and lath work. Tile or overlay goes on Day 3+. We give you a firm timeline before we start — no open-ended projects.
Serving all of Arizona — residential and commercial