Installing a DIY Under Deck Drainage System
If your deck is elevated or on a second story level, you’ll want to consider installing a DIY under-deck drainage system, which diverts water away from the deck and into gutters so the area beneath the deck is dry and useable.
After installing an under deck drainage system, you’re free to use the space below the deck for a patio giving you a lovely retreat during inclement weather. You can also use the space to create a waterproof under deck storage.
Trex RainEscape by Trex Company, named among the 2019 Remodeler's Choice 100 by Qualified Remodeler Magazine, is simple to install and affordably priced. Trex RainEscape is installed before you lay the deck boards. It is an over-the-joist deck drainage system. This type of deck drainage system allows you to finish the underside of the deck (which is the ceiling of the patio below) with utilities for electricity, lights, ceiling fans, entertainment components and more.
Tools & Materials Needed for a DIY Under Deck Drainage System
- Utility knife or scissors
- Staple Gun
- Caulk Gun
- Trex RainEscape Downspouts
- Trex RainEscape Trough
- Trex RainEscape Butyl tape
- Trex RainEscape Butyl caulk
- Optional: Trex RainEscape Soffit Lights, ceiling fan, TVs or other elements
How To Waterproof Under Your Deck with a DIY Deck Drainage System
This article shows the installation basics for waterproofing the space under your deck using troughs that run between joists and empty into the system’s downspouts. If your deck has unusual angles, oddly-spaced joists, railing posts inside the framing or other special cases, you will may need to modify the troughs and downspouts to fit the space but the approach is pretty much the same: Install downspouts and trough so that water flows to the gutter, then completely cover all seams with butyl tape.
Trex RainEscape is installed over the joists before the decking boards are installed, ensuring no water touches the joists. Protecting the deck foundation from water is essential for preserving the longevity of the deck.
Some homeowners ask how to waterproof under an existing deck. This is not recommended, as it would require a system installed under the joists. An under-the joist deck drainage system allows water to run through the deck boards over the joists and into gutters under the deck. Repeatedly exposing the joists to water will result in wood rot and decay.
Cut your downspouts and install them along one rim joists and/or the ledger board
1. First, install the downspouts. These are made to fit between joists spaced 16 inches on center if positioned in one direction. If your joists are 12 inches on center, simply face the downspouts in the other direction. Check that the downspouts’ funnels will extend down at least 1 inch into the gutter you will install.
The downspouts are 10 inches tall, so they fit well with 2x10 joists. If your joists are smaller, cut the funnels as needed, so they extend. If you have 2x12 joists, use extenders. Cut out a panel along the perforation using a utility knife or simply tear by hand. Position a downspout in each framing bay at the end where you will put the gutter, and staple them in place.
Tuck the trough under the flashing to the wall
Roll out the trough. Staple and cut to length.
3. Unroll the trough panel and staple it on one side with its edge flush with the edge of one joist. Pull the trough taut as you work. When you reach the downspout, tightly reverse-roll the trough to remove its roll “memory.” Then, cut it to length so its end falls near the center of the downspout hole.
Staple and roll out more trough
4. taple the other side of the trough. Follow the guideline on the panel. This will automatically create a slight slope for water to run down. Continue installing trough panels.
Fill in the small areas at the angles
Apply the tape at the seems and joints
6. Use a utility knife or scissors to cut any excess overlapping trough material. Starting at the house and working toward the downspouts, apply the butyl tape provided with the system by removing the paper backing as you unroll it. Work carefully to keep the tape from wrinkling, and press it firmly in place so it forms a tight seal at all points.
Nice and dry!
Install your gutters
Install your decking
You can learn more about waterproofing your deck in this article. With a deck drainage system, you’ll easily learn how to keep the area under the deck dry. Additionally, here is a reputable place to buy Trex RainEscape.