Waterproof balcony decking
Balcony Waterproofing With Real Deck Boards
AmeriDex PVC boards lock onto the Dexerdry seal, so rain sheds off the top of the balcony instead of dripping through. You get a deck board surface and a dry space below, without fiberglass or a concrete slab.
Why builders use it on balconies
Where the water goes
Deck boards vs membrane vs concrete
| AmeriDex + Dexerdry | Membrane or coating | Concrete | |
|---|---|---|---|
| What you walk on | Deck boards | The membrane surface | Concrete |
| Where water is stopped | At the boards, sealed seams | At the sheet over the sheathing | At the slab, until it cracks |
| Weight on the structure | Standard deck framing | Sheathing plus membrane | Heavy |
| Color choices | 7 PVC colors | Depends on the product | Depends on the finish |
For decks over a patio, see second-story deck waterproofing. For the board itself, see PVC decking made in the USA.
Balcony planning checklist
- Outdoor space below only. Never install over interior living space.
- Boards run away from the building (the perpendicular method) on balconies set into a building.
- Frame 8 inches at the wall for the gutter: 5 inches to the outside of the frame plus 3 inches to the next joist.
- Joists at 12 or 16 inches on center, never 24.
- Slope 1/8 inch per foot away from the building, planned at framing.
- Flash the ledger before decking, and set L-shaped flashing into caulk where the boards meet the wall, about 3 1/2 inches up.
- Overhang the outer board ends at least 1 3/8 inch and cut a drip edge underneath.
- Want a ceiling below? Use a vented vinyl or PVC soffit, not wood.
More detail is on the install help page, in deck ledger flashing, and on contractor resources.
Frequently asked questions
Can AmeriDex be used to waterproof a balcony?
Yes. The Dexerdry seal that AmeriDex boards lock onto is a more affordable and faster alternative to fiberglass or concrete balcony construction. Rain sheds off the top of the boards instead of dripping through the gaps, so the area below stays dry.
Can I install it over a room or other interior living space?
No. Never install the system over interior living space. It is made for balconies, decks, and porches with outdoor space underneath, such as a patio, a covered entry, or storage.
Which install method do balconies use?
Use the perpendicular method, with the boards running away from the building, for balconies set into a building. That layout needs a gutter at the wall, so allow 8 inches of framing space there: 5 inches to the outside of the frame plus 3 inches to the next joist.
Why not just pour a concrete balcony?
Concrete balconies are expensive and heavy, and they can crack and let water through to the ceiling below. The AmeriDex approach creates a dry zone with standard grooved decking on conventional framing.
Where does the water go on a balcony?
Water runs across the top of the boards on a slope of 1/8 inch per foot away from the building and sheds off the overhanging board ends past the drip edge. At the building wall it drops through a small planned gap into a gutter, and the wall itself is flashed and caulked.
Can I put a ceiling under the balcony?
Yes. Use a vented vinyl or PVC soffit that allows airflow; wood ceilings are not recommended. Provide at least 1 1/2 inches of continuous ventilated screen at the fascia, or use a vented soffit throughout.
Planning a balcony? Send us the size.
Share your balcony dimensions and how it attaches to the building, and we will send a written quote. Free color samples ship to your door.
Get a free quote Find a dealerRelated reading: Waterproof decking guide · Second-story deck waterproofing · Dry usable space under a deck · Cost guide · How the system works