Structural Plastic Lumber and General Installation Guidelines

1. Structural Ability

Structural plastic lumber is recommended for structural use but care needs to be used in the design of the structure. It is not a direct replacement for standard wood materials. In most cases the deflection will control the needed size of boards. Span charts (see below) can be used to determine the approximate size for normal applications. If you have other applications please consult with us or a licensed engineer or architect so they can take into account the anticipated maximum loads, long term creep and deflection issues associated with Structural plastic lumber.

2. Expansion/Contraction

Structural plastic lumber expands and contracts along its length based on temperature. A calculation for change in length in inches can be done by using 0.000034 IN/IN/degrees multiplied by its length in inches, and the temperate change of the board. This expansion and contraction on short lengths is minimal, but if you are using longer lengths and in a climate with large temperature changes you need to take in account the expansion and contraction of the board in the design. Non-Structural material is slightly higher.

3. Fastening

When fastening typically a size #10 stainless steel screw or larger is recommended. Generally pre-drilling makes installation easier and oversizing holes can allow for and minimize any unnecessary expansion and contraction pressure on fasteners. Each board or deck board should be fastened with at least 2 screws per support or joist and should be at least ¾” from the edge or end of the board. Stainless steel fasteners are recommended, although galvanized can be used.

4. Butt Joints

When butting Structural plastic lumber against any wall, fixed surface or other boards (if necessary), they should be securely fastened to the nailer or double joist with a gap allowing for expansion. Another method can be utilized called a feature board or a perpendicular board to allow for expansion and contraction in two separate locations. Double joist with flat joist in between. The size of gap should be determined based on weather conditions at the time of installation – the closer the temperature is to the usual high temperature for the year, the smaller the gap. (See chart below). The structure or deck should be designed to minimize butt joints. However, in the event that joints are required, a wide or double joist underneath the butt joint should be used, with the shortest possible length boards. Boards should be securely fastened with a row of screws on each side of the joint, 1” from end of the board. Always keep deck boards out 1/4” from permanent structure.

5. Rip Cutting

Rip cutting is not recommended on any plastic lumber. Much of the strength of the board is on the outside surface of the boards. Ripping boards can cause the boards to warp or curl.

Should there be any questions regarding these instructions, please contact your sales representative for more details.

*Failure to follow these instructions may void warranty.