How to install a deck with composite decking?

When you decide to install COOWIN composite decking. It is important to follow the COOWIN installation instructions. Thermal expansion is always something to be aware of when dealing with plastics.

In most climates, temperature fluctuations are sufficient to cause problems with deck spacing from summer to winter. Composite decking tends to grow and shrink over the length of the board as it heats and cools. Proper spacing will allow some movement without bending and deforming.

Preparation before installation

Before you decide to install any composite decking system. It is recommended that you check with local building codes for any special requirements or restrictions.

The diagrams and instructions outlined in this guide are for illustration purposes only and are not meant or implied to replace a licensed professional. Any construction or use of wood plastic composite.

WPC products must be in accordance with all local zoning and/or building codes. The consumer assumes all risks and liability associated with the construction and use of this product.

Please read carefully and refer to the corresponding instructions during the installation. The methods and accessories involved in this instruction are only recognized by the warranty. Failure to follow this instruction or use another installation method besides this instruction may invalidate the warranty.

Read before you start


When dealing with any type of construction project. It is necessary to wear appropriate safety equipment to avoid any risk of injuries. When handling, cutting, and installing, the following safety equipment is recommended but not limited to. Such as gloves, respiratory protection, long sleeves, pants, and safety glasses.


Standard woodworking tools may be used. It is recommended that all blades have a carbide tip.

Standard stainless steel or acceptable coated deck screws and nails are recommended.


A clean, smooth, flat, and strong surface is needed to install WPC products correctly. Please check with local building codes before ever installing any type of decking. If the installation does not occur immediately, WPC products need to be put on a flat surface at all times. Never ever should it be put on a surface that is not flat.


Plan a layout for your decking before starting it to ensure the best possible-looking decking for your project. Building codes and zoning ordinances generally apply to permanent structures. And means anything that is anchored to the ground or attached to the house. So nearly every kind of decking requires permits and inspections from a local building department. We recommend drawing out a site plan of your proposed project that you intend to do to minimize errors and make your project perfect.


WPC products are not intended for use as columns, support posts, beams, joist stringers, or other primary load-bearing members. WPC products must be supported by a code-compliant substructure. While WPC products are great for retrofits. ButWPC products can’t be installed on existing decking boards.


WPC products can’t be directly installed onto a flat surface. It must be installed onto a substructure. So there is adequate and unobstructed airflow under the decking to prevent excessive water absorption. A minimum of 25 mm of the continuous net free area under the decking surface is required for adequate ventilation on all decking. So air can circulate between adjacent members to promote drainage and drying.

Heat & Fire

The continuous high temperature generated by fire or other heat sources will cause damage to outdoor decking. Therefore, do not install the decking near a heat source such as a fireplace.


Acclimating at least 2 days prior to installation is recommended. Acclimating the boards will get rid of any unwanted shrinkage issues seen during and after installation.

If the products won’t be used for a long time. Please keep the package complete and store them in a well-ventilated and drained indoor environment, avoiding direct sunlight and rainwater. Products must be raised up by joist and stacked neatly on an even and solid ground. Uneven ground will cause the products to deform and warp. The spacing of each joist should be no more than 500mm. Do not store the products by putting them on the ground directly.

Please cover unused products during construction. Avoid scratching the deck surface caused by sand and gravel generated by construction operations.

Please lift and drop the products gently, and it is forbidden to drag or extract the products.

Decking support structure

Framing: It’s recommended that code-compliant materials. Such as pressure-treated wood or metal tubes, be used for the framing. Please follow the manufacturer’s instructions for proper installation. The framing must be level without undulations, and the joist spacing should not exceed 14’’(350 mm).

Ground treatment

A smooth and solid ground base that ensures good ventilation and drainage is crucial to the longevity of the decking. Please exercise proper ground treatment methods according to the ground condition at the job site. Here are the tips for some specific ground conditions. Such as sandy land, soft soil, and grassland:

Build a concrete foundation

Dig holes in the ground with a suitable interval and depth below the frost line and then pour concrete in. They act as a foundation for lumber or metal framing. Then you can install the decking on the frame.

Use ground screws

Fix the ground screws to the ground at a suitable interval. Fixing the metal framing to the ground screws. Then you can install the decking on the frame.

Apply surface hardening treatment

Dig a depth of roughly 15-4/5’’(400mm) depth (depending on the soil quality) under the ground. Then, ram the soil, lay the waterproof material, surface it with gravels and concrete slates.

After that, lay the joists and install the composite decking. No construction measures that could cause damage to the surface structure shall be adopted on rooftops, balconies, and patios, as the waterproof layer might be damaged or other safety concerns could result. You can secure the joists with concrete before installing the decking.

Joists must run in the direction of the pitch of the roof to facilitate proper drainage. If necessary, consult your local building code authority for information about the construction on roofs.


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