5 Steps to Install Composite Wood Deck


    – Step 1: Define your composite decking project

    – Step 2.0: Install the joists on a concrete slab

    – Step 2.1: Install the joists on a natural floor

    – Step 3: Install the first row of deck boards

    – Step 4: Install the next row of boards

    – Step 5: Finish the composite deck by installing the edge boards

As soon as the warm weather arrives, the deck becomes a real additional living space. As a link between the house and the garden, it is a pleasant place to relax and have lunch or rest. Composite wood has many advantages: it is light, easy to install, and durable over time, without requiring maintenance. You can install the composite deck on a concrete slab or a natural ground. Follow these detailed explanations to learn how to install a composite deck.

1. Define your composite decking project

Choose the location of the deck

    – Choose a location near the house for convenience.

    – If your deck is not attached to the house, make sure it is accessible through Japanese steps or graveled paths.

    – Orient your deck to the south or west to get maximum sunlight.

Good to know: avoid a north-facing orientation to avoid having a damp, cold, and dark terrace.

    – A terrace facing the wind is not very pleasant, but it is possible to remedy this problem by planting a hedge or wooden fences.

Determine the size of your deck

Think about how you will use your deck to determine its size.

    – For a family dining area with a table and chairs, 10 to 15 m² is sufficient.

    – For a relaxation and reception area, plan for at least 30 m².

Draw a plan for your deck

    – Choose the shape of your terrace, L-shaped, rectangular or rounded, according to your tastes but also the configuration of the garden.

    – Draw a plan on paper, noting all dimensions.

Good to know: make a view of the garden to visualize your project better.

Determine the type of deck support

You can install a composite wood deck on natural soil or a concrete slab.

    – If you already have a concrete deck, use it as a base.

    – If your substrate is natural soil, follow the recommendations for installing a deck on natural soil.

2.0 Install the joists on a concrete slab

With a concrete slab, the joists are fixed directly on it.

Place the 2 joists perpendicular to the house

    – Place 2 joists of the same size perpendicular to the wall of the house.

    – Insert an expansion block between the joists and the wall.

    – Make sure that they are square.

Attach the 2 joists

    – Drill a pilot hole at both ends of the joists, then every 70 cm or so.

    – Countersink the screw heads using a larger drill bit.

Good to know: do this operation carefully so that the screw heads do not protrude from the wood. 

    – Drill the slab through the joists with a concrete drill bit.

    – Then, insert knockout dowels into each hole to secure the joists.

Place and fasten the intermediate joists

    – Place the intermediate joists every 30 to 40 cm.

    – Check that they are horizontal and square.

    – Attach the joists as before.

2.1 Install the joists on a natural floor

Before installing the joists, prepare your natural floor to obtain a horizontal deck at the desired height.

Prepare the ground

    – Mark out the decking area.

    – Place a geotextile film on the ground, covering the entire surface.

    – Place a bed of sand on the film.

    – Pack it down over the entire surface with a roller.

    – Place concrete slabs at each corner, then distribute them evenly. They will serve to stabilize the joists.

Good to know: you can replace the concrete slabs with adjustable blocks. To fix the joists to the blocks, refer to the instructions provided.

    – Check the level of the whole by placing a mason’s rule on the slabs and a spirit level on it. If necessary, adjust the level by adding sand.

Install the joists

    – Assemble a frame of joists around the deck by screwing them together, edge to edge.

    – Double the 2 sides by laying 2 joists, one against the other, on the sides where you will lay the first and last row of boards.

    – Check the squareness of the frame by measuring the diagonals. They must be identical.

Good to know: with a string, take the length of the first diagonal. Then check that the second diagonal is the same length.

    – Install the intermediate joists inside the frame, approximately every 30 to 35 cm.

3. Install the first row of deck boards

5 Steps to Install Composite Wood Deck

Place the first board on the joist

    – Place the first decking board in perfect alignment with the joist.

    – Insert a shim between the wall and the joist to allow for expansion.

    – Then screw the board into the joist. – Drill pilot holes and countersink the screw heads.


Insert fasteners and continue the installation

    – Insert the fastening clips into the board’s groove, centering them on each joist.

    – Screw the clips lightly (without locking them) into the joists.

    – If necessary, complete the installation with another board up to the end of the deck.

Caution: the board joints must be in the middle of a joist.

4. Install the following rows of boards

    – Place a board in the second row along the first row.

Note: If the side of the deck is against a wall, insert a shim between the wall and the board.

    – Insert the clips into the board’s groove and snap them into place.

    – Continue installing the second row in the same way, making sure to position the board joints in the middle of a joist.

Good to know: if you want to install the boards with staggered joints, mark the distance needed to reach the middle of the joist and cut the panel to the correct size.

    – Once the line is installed, adjust the alignment of the boards by tapping on the end of the line and the side with a mallet.

    – Then screw the clips completely onto the joists.

    – Install the other lines in the same manner.

5. Finish the composite deck by installing the edge boards

    – Measure the height of the deck, then subtract several centimeters to allow for rainwater drainage and air circulation.

    – Transfer this measurement to the width of the boards and cut them to remove the grooved side. This will give you a clean edge with no grooves.

Good to know: if several sides of the deck are to be covered, cut the end of the boards at a 45° angle using a miter box to ensure a perfect finish to the corners.

    – Screw the edge boards into the joists.

Your deck is finished, and you can enjoy it as soon as the first rays of sunshine arrive!

Materials needed to install a composite deck

Miter box

Wooden wedge

Hammer dowel

Carpenter’s pencil


Milling cutter


Carpenter’s mallet

Tape measure

Spirit level



Percussion drill

Mason’s rule

Arm roller


Circular saw

Hand saw

Wood screws