How is above-joist deck drainage priced?

AmeriDex is priced by the lineal foot of deck board, because the board and the Dexerdry seal together are the drainage system. Use the on-page calculator to estimate materials for your own deck size, then request a written quote from an authorized dealer for exact numbers.

Can I estimate materials for my deck?

Yes. Enter your deck width and length in the calculator on this page to see the square footage, the lineal feet of board it takes, and an estimated material figure. A dealer will confirm boards, lengths, accessories, freight, and any final numbers in a written quote.

Is above-joist drainage cheaper than a below-joist system?

Not necessarily. Compare complete, equivalent project scopes. AmeriDex integrates drainage at the deck surface. Separate above-joist membranes or troughs sit beneath the boards, while below-joist systems collect water under the framing. Decking, drainage components, labor, flashing, trim, and any finished ceiling should be itemized before comparing quotes.

Does the material figure include the seal?

Yes. The lineal-foot material figure covers the cellular PVC deck board and the Dexerdry TPE seal that sits between every board. There is no separate line item for the drainage layer, because the deck surface is the drainage layer.

Can I install it on an existing deck?

AmeriDex is installed as the deck surface, so it suits new decks and qualifying re-decks where the old boards are removed. A builder must confirm framing condition, spacing, drainage pitch, flashing, fastening, and the current installation requirements. It cannot be added beneath boards that remain in place.

Above-Joist Deck Drainage Cost Guide

How above-joist deck drainage is measured

Above-joist drainage is priced by the lineal foot of board, not by the square foot, because the board is the drainage system. A 5.5 inch board face plus the 3/16 inch gasket gap covers 5.6875 inches of deck, so one square foot of deck takes about 2.11 lineal feet of board. Here is what that looks like on four common deck sizes.

Deck size	Square feet	Linear feet of board
12 x 16	192	405
16 x 20	320	675
16 x 24	384	810
20 x 24	480	1,013

Linear feet are rounded to the nearest whole foot. Boards ship in fixed lengths, so your dealer will round up to whole boards and allow for cuts. Enter your own dimensions in the calculator below for a material estimate.

Estimate your deck

Enter your deck dimensions to see the square footage, the lineal feet of board it takes, and the estimated material cost.

What the material estimate includes

The lineal-foot material estimate is a planning number that covers the decking and Dexerdry seal:

Cellular PVC deck boards in the color and length you choose
The Dexerdry TPE seal between every board, which is what makes the surface watertight
Fastener type and quantities must be confirmed in the written quote; do not assume they are included in this planning allowance.

What the estimate does not cover:

Labor, which your builder or dealer quotes separately
Framing: joists, beams, posts, footings, and the ledger
Railing
Trim and fascia
Permits and inspections

Because the drainage is part of the deck surface, there is no separate drainage product on the invoice. See how the two-part system goes together.

How above-joist and below-joist drainage costs differ

Compare the same project scope before comparing prices. Surface-integrated systems combine decking and drainage; separate above-joist systems add a layer beneath the boards; below-joist systems collect water under the framing.

Separate above-joist systems can also intercept water above the covered framing. Installation location, access, accessories, and finishing details affect the quote. No generic labor or lifetime-savings claim replaces a project-specific takeoff.

Can it go on an existing deck?

Here is the honest answer. AmeriDex is installed as the deck surface, with the seal placed between every board as the boards go down, so it is a new-build or re-deck system rather than something that can be slipped in later.

During a re-deck, where the old boards come off and new boards go on, it can often be installed on your existing joists, provided a builder confirms framing condition, spacing, drainage pitch, flashing, fastening, and all required installation details. That is a common and cost-effective path: you are already paying for new decking, and the drainage comes with it.

What it cannot do is go underneath a deck whose boards stay in place. If that is your situation, a below-joist trough or membrane retrofit is the category to look at, with the trade-off that the framing keeps getting wet. Not sure which one you are? Send your dimensions through the quote form and a dealer can assess whether your framing can carry a re-deck.