The installation method used will need to be adapted to the particular layout of the wood decking installation site.
Wood decking can be installed over concrete slabs, on supporting foundation posts, or by using height-adjustable pedestals to support the battens.
Boards can be fixed in place invisibly using hidden fastening and fixing systems, concealing screws and clips from view.
The technical reference text governing site preparation and undertaking of installation on external floors is French industry standard DTU 51.4.
The decking boards must be stored horizontally, spaced apart, and clear of the floor.
Stage 1: Installing the battens.
The battens must be made from class 4 rated wood. This is usually wood of an exotic species and must be at least equal in density to the species chosen for the decking boards. The battens must be at least twice as thick as the boards they will be supporting. The space between the battens should normally be about 35 cm. When installed in the direction of the gradient, the battens will not impede rain water runoff.
When installing over an existing floor surface, such as a concrete slab, or tiling, the battens can be either screwed or fixed directly to the surface, or set on concrete or PVC supports. They can also be installed on adjustable pedestals, thus avoiding problems caused by variations in floor height.
Installing battens on adjustable pedestals
The most practical way of installing is to use height-adjustable pedestals. The pedestals make it possible to adjust for differences in floor height and also permit installation over a gradient, thus providing good rain water drainage. They also make it easier to adjust for a height difference between the decking surface and adjoining access threshold.
Pedestal installation can be used with various floor surface types (concrete, stone or wood). Individual pedestals can very easily be replaced or temporarily removed, when maintenance is required for example.
The mechanical properties of pedestals offer a further advantage: they are robust and do not suffer damage when the decking is used. Additionally, by supporting the decking at a regular distance from the supporting surface, pedestals allow for good ventilation and prevent the underneath of the decking from degrading.
Be careful to ensure the load is evenly distributed by using at least eight pedestals per m2.
Installing on open ground: the battens form the framework over which the decking boards are installed. They rest on concrete slabs that provide stability for the whole structure. They can also be installed on height-adjustable PVC pedestals. The battens must all be installed at exactly the same level.
Stage 2: Preparing the supporting structure
Over an existing hard surface:
Install the battens using screws with rawl plugs, or embed them directly into screed. Warning: when installing at a block of flats, do not pierce the building’s damp-proof course.
On grass or bare ground:
- Lay a geotextile (insulating) membrane to prevent weeds from growing. Cover the whole terrace area, ensuring the insulation sheets overlap by 20 cm.
- Add a layer of gravel or compacted sand.
- Next install the battens, forming a framework matching the dimensions of the planned decking.
- Every 50 cm, to support the battens, place concrete paving stones or slabs, cement blocks, or PVC pedestals all adjusted to the same level. The battens must be perfectly flat (spirit level flat). Take care to install perpendicular reinforcing pieces between the battens. Ensure that the framework is perfectly square.
It is advisable to double battens at the points where they coincide with decking board ends. This ensures better water evacuation and better seating of the boards in case of expansion.
Stage 3: laying the boards
Position the boards in place, making sure they are all laid on the same side (smoothed vs grooved, concave vs convex).
If the decking adjoins a house, begin from the wall of the building, using a spacer to ensure an expansion gap of 5 to 10 mm is left. This expansion gap must be left wherever the decking boards’ edges lie next to a hard surface.
A gap of 5 to 10 mm must be left between decking boards to enable rain water runoff and to allow for wood expansion.
When using either of the two fixing methods described below, the boards must be laid in an alternating brick bond pattern to make it easier to work with the wood:
- Fixing boards onto battens with screws
The decking boards can be screwed directly onto the battens. When using this method, both ends of every board must lie over a batten.
To simplify the screwing down process it is advisable to drill the holes beforehand to make positioning easier.
Be sure to choose the right equipment: use stainless steel screws, and drill bits suitable for hard materials. Plan to use two screws across the board widths and ensure that the screw heads are flat. Screws are best countersunk to avoid any risk of protrusion. This will make your decking safer and improve its appearance.
- Fixing with hidden clips
There are numerous hidden fixing systems available for wood decking boards. They work on the principle of clips fixed to the battens. The clips then slide into grooves on the decking boards, attaching them firmly to the battens. These systems are only suitable for decking boards with a grooved profile.
Stage 4: finishing touches
To complete your wood decking installation, create a frame around the exposed edges of the decking using boards with the groove removed.
To preserve the chosen wood species’ original colours, we recommend the use of a decking brightener and/or wood saturator after the first year, repeating the operation annually thereafter.
Source: guide de conception et de réalisation des terrasses en bois, FCBA and ATB
This installation advice is based on French building code DTU 51.2. It is provided for information purposes only and does not entail the liability of Décoplus in any way. The advice given here will, nonetheless, enable you to efficiently carry out the installation of your new flooring yourself. However, if problems are encountered, it is advisable to engage the services of a professional rather than risk irreversibly modifying your newly purchased flooring.