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How to construct a wooden deck?



A quality wooden deck

Wood, a noble and living material, is often exposed to intense stress when used during the installation process of a terrace : bad weather conditions, differences in humidity and temperature, moisture from underneath, UV, mechanical stress, …

Achieving an outdoor terrace of quality, which is stable and lasts for a minimum of 20 years, requires great rigor in the design and choice of materials. Quality is a key issue to satisfy customers as well as it gives back the nobility that a wooden deck deserves.

When placing a wooden deck, your choices about materials and implementation techniques will have a strong influence on two aspects :

Sustainability: A wooden deck can be degraded more or less quickly (between 5 and 30 years) under the effect of various biological circumstances (insects, moisture), depending on the quality of the materials, ventilation and compliance with the correct method of implementation.

Stability: Wood is subjected to weather, it swells and shrinks significantly, which can lead to deformation such as warp, uplift, cupping and bending, … of the wooden decks.


The wood

The wood

Choose the decking

Respect the width-thickness ratio of the wooden deck

The width of the deck should be a maximum of 7 times its thickness. For example : 21 * 7 = 147 mm maximum width. In case of non-compliance with this rule, the higher the risk of deformation of the decks.

Choose your decks carefully

Be careful when you choose your decks. Make sure the decks are not bent or cupped or show irregular patterns in the wood fibre.
Remember to check whether the thickness of your decks is in line with the thickness proposed by your wood supplier.

Check the dryness of the deck

Some species of wood have more grains than others : Cumaru, Yellow Balau, Massaranduba, … It is necessary that these wood species are KD dried (Kiln Dried). On average, the dryness of the decks should be around 16 %. Check the dryness with your timber dealer and require the information to be stated on the invoice (in case of dispute, you will be protected). If necessary, you can use a moisture meter to check the dryness of your decks.

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Choose the wood structure

Service class

The service class structure of the wood is mandatory or greater than that of the decking. It is easier to replace a deck board than a complete structure. It is better to focus more on the quality of the wood than the deck structure.


Never put the wood structure in direct contact with the ground to avoid premature rotting of the wood. Always use shims or polymer pads to isolate the joists on the ground. It is important to have some space between the deck and the substructure, by using a thermal bridge such as pfs® Hapax D-Pro or the invisible pfs® Hapax Fixing.

Set the distance between the joists

It is better to reduce the distance between the joists, because it will reduce the risk of deformation of the deck boards.

The joists

The minimum height and width of the joists has to be 40 x 60 mm.



General rules

Never place the wood in direct contact with the ground

The space between the decking and the ground allows the terrace to be well ventilated, which improves the stability and the life span of the terrace. Always use shims or polymer pads to isolate the joists on the ground. The distance between the decks is about 4 and 6 mm for a terrace that is about 10 cm high.

Create or maintain a drainage slope for rainwater

Make sure to provide a slope of 0,5 to 1 cm per meter.

Always create a decking frame

The decking frame is made of several joists, placed at a certain distance from each other, forming a rectangular structure. This structure offers more strength and stability to the wooden deck.

Double the joists

Always double the joists. It will offer better support to the wooden deck and lower the risk of water damage.

A roof terrace

Use shims or adjustable polymer pads

Never perforate the waterproof membrane of the roof to avoid the risk of water infiltrating the building. Use shims or adjustable polymer pads to isolate the joists on the waterproof membrane. The shims or pads make sure the membrane is not perforated and still allows drainage of the rainwater.

A terrace on hard ground

Use shims or adjustable polymer pads

When installing a terrace, it is necessary to use shims or adjustable polymer pads to isolate the joists on the floor.

Fixing the structure to the floor 

In most cases you will drill holes in the floor to attach the joists using concrete screws or hammer nail plugs.

A terrace on soft ground

Use a geotextile

Start placing your geotextile on the ground to prevent the regrowth of plants through the terrace.

Use a fixed batten on the wall

When the terrace has to be attached to the house, you can use a fixed batten. This batten will function as a general reference for the entire terrace and it will serve as one of the primary support joists.

Use an environmental friendly construction

Use the Hapax Rock screw foundations instead of a concrete foundation for your terrace. The soil will remain intact and the resistance of the screw foundation is similar to the concrete one.



General rules

The space between the deck boards

The spacing between the deck boards depends on the moisture content in the decks and the height of the deck. The higher the terrace, the lesser space between the deck boards. The average spacing is 4 to 6 mm for a terrace height of 10 cm. 


It is essential to treat the alignment of the first deck boards row. For this we will use a masonry cord. Check the alignment every 7 boards.

Use a thermal bridge

It is essential to use a thermal bridge between the decks and the joists to avoid moisture stagnation. For example : pfs® Hapax D-Pro, pfs® Hapax Fixing, … 

Fixing with screws

Choice of screws

It is mandatory to use special terrace screws to ensure a good performance of the screw in the decks. It is important to calculate the length of the screw : minimum 2 x the thickness of the deck. It is better to choose a longer screw than one that is too short.

Screwing instructions

The screw must be placed at least 2,5 cm from the edge of the decking boards.


For a perfect finish, we recommend pre-drilling the decking boards. This pre-drilling is imperative for hardwood screws with a density of 850 kg/m3. Also keep in mind the alignment of the screws. At this time, the Hapax G-Deck tool will come in handy.



General rules

Alignment between the deck boards

The decks should be aligned perfectly. They will have the same width and regular spacing.

The use of finishing decks

The finishing decks are used to hide the structure that hold the actual terrace. However, always make sure there is enough space for ventilation to protect the terrace from moisture. This finish gives the terrace a really professional look.


The final sanding with 80 grit will eliminate any wood surface defects, such as oil stains, your pencil marks and splinters caused by sawing the decks.


Remove moss and debris

Once a year, during the spring, you will have to apply maintenance to your wooden deck. Use a brush to wipe of all the moss and debris. Once you have done that, use your pressure cleaner to remove the remaining dirt and stains. 

Preserve the natural colour of the deck

Over time, the beauty of a natural wood deck can lose its lustre as the UV (ultraviolet) rays from the sun break down the wood’s structure. If the deck has taken on a dull grey look, the problem may be easier to fix than it looks. You can clean your wooden deck with soap and water or bleach, or any other commercial powder or liquid concentrates on the market. This should solve the problem. After cleaning the deck, you can apply a finish that contains UV blockers and a pigment to keep the UV rays from turning the deck grey again. 


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