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Installation & Maintenance
How to Install Capped Composite Decking Over Concrete
November 05 2016
Decking Installation

When temperatures start to rise and the sun makes its appearance in spring, improving your back yard can truly create added value and enhance the look and feel of your space. If you have a concrete patio that you want to transform into a more beautiful and impactful outdoor space, installing capped composite decking over the patio is not only a great choice, but it’s actually pretty easy to do, as well. This type of deck is called a “floating deck” even though it’s not really floating.

This guide will provide you with the basic instructions for installing a capped composite deck over an existing concrete patio. For starters, any time you’re installing a deck over an existing hard surface, you’re going to need a sleeper system.

1. What Is a Sleeper System?

A sleeper system is a substructure that sits between the concrete and the decking. It is comprised of joists that raise the deck slightly above the surface of the concrete. The space between the concrete and the decking material is essential because it allows for air circulation and water drainage to occur, thus protecting the capped composite deck boards from the risk of excessive moisture-related damage.

Another benefit of sleeper systems is that it makes it easier to clear out any accumulated debris from under the deck. Of course, before you begin building your floating deck, you should always check with your local zoning commission to find out if there are any special building codes you need to be following.

2. Factors to Consider Before the Building Process Begins

When building your sleeper system, there are certain things you need to consider before you begin the process, including:

  • Solve any water run-off or pooling problems on the patio before starting.
  • Mark the sleeper locations on the patio before you start drilling (remember to note the extra sleepers if you’re adding stairs or railings to the deck area).
  • Pre-drill holes for your concrete screws.
  • Sleepers need to be at least 1-1/2 inches in both height and width.
  • Sleeper systems should never be installed on gravel, sand, dirt, or on concrete pavers (although spacers are permitted for improved drainage).
  • Choose sleepers that are resistant to wet conditions and rot, especially if harsh weather conditions are a factor in your area.
  • Sleepers should be installed directly on the concrete with screws penetrating the concrete by at least one inch.
  • Sleeper joists should be installed parallel to the direction of water run-off.
  • Joists should be spaced according to standard joist space codes (no greater than 16 inches on center).

3. Installing Capped Composite Decking Over the Sleeper System

With your sleeper system installed, you should now cover the sleepers with flashing tape. This is not a mandatory practice, but the flashing tape helps protect the tops of your sleepers from absorbing water. This step takes on greater importance if you’re using common grade lumber, as it will rot rather quickly if it remains damp.

Next, your capped composite decking gets installed just as it would if you were installing the boards on a traditional deck. The embossed side needs to be the side that’s facing upwards.

It’s important to note that the surface on TwinFinish, ReliaBoard, DockSider, Fascia and Riser boards are directional in manner. A notch has been added to one side of the planks so you can better identify the proper direction. When installing, the notched edge needs to be laid to the same side throughout the entire installation for a consistent appearance.

Additionally, TimberTech’s Fascia board and Riser have one long beveled edge on the front and back. With these two board types, the beveled edge needs to be laid to the same side throughout the installation in order to ensure a consistent appearance. This is important to remember if you rip a piece. Note the location of the bevel before you rip, so you don’t accidentally install the board facing in the wrong direction.

If you’re installing two different colors of boards for your deck, then you can screw the accent color boards into place temporarily to act as guides for the primary color boards. To cover the ends of the sleepers, install deck fascia board.