The most important points for a long-lasting wooden deck

1. lack of ventilation

2. Strong swelling and shrinkage behavior of the wood

3. inferior quality of the materials used

If we do not match the required materials to each other and pay attention to their quality, the user of the patio will not enjoy it for long. This starts with the decking, how was the board cut from the tree, what wood or material do I use for the substructure, what happens under the substructure and how do I fasten it properly. The best way to see the differences in quality is to take the plank as an example. With native woods, we should always make sure to install rift/half-rift goods (standing annual rings). This is not so essential with modified woods, as these only have very reduced swelling/shrinking properties. However, it can generally be said that upright annual rings are better than horizontal ones... core boards should be avoided.

4. poorly executed details

Let's move on to the execution details. Here it's all about small causes with a big impact. Here, for example, the distance between the screw and the end grain is too small, the distance between the substructure is too large, and the thicker the plank, the smaller the distance between the substructure should be. Not because of the load-bearing capacity, but because of the forces generated at the fastenings. As already mentioned, always ensure sufficient ventilation. Rain and snow always cause water to come through the joints from above and can then no longer dry out at the bottom.

The sensible construction

1. At SIHGA, we have provided our customers and everyone else with the most important basics online. These are also always in line with the recommendations of Holzforschung Austria.
   
2. Furthermore, there are extensive tables from which you can see which fastening is best for which plank types, visible...
   
3. ...and also not visible. If you are interested, you can view and download this at any time at...
   
4. ...www.sihga.com 
   
5. So, substructure spacing should always be less than 50 cm, regardless of the plank thickness. As already mentioned, this also has a massive effect on the fastening. In other words, the thicker the plank, the smaller the distance between the substructure!
   
6. The substructure is best supported in a tapered manner in order to achieve optimum load distribution, which is very important in the flat roof area. The distance between the bearings can be used up to 1.10 m with our systems, but this should be reduced to 70-80 cm for small aluminum tubes or standard wooden battens.
   
7. The longitudinal joints of the boards should be designed with a joint, as should the surface. These areas should be made with two substructures, so that the end grain can always dry out and it is possible to maintain a healthy distance between the screw and the end grain.
   
8. The screw distance to the end grain should always be at least 50mm, in general the boards should be pre-drilled, we have a screw for this, with which this can be done in one operation. It is important that there is air between the screw and the drill hole to allow movement.
   
9. The same applies to the edge of the planks, otherwise longitudinal cracks will always occur here along the grain
   
10. The planks should have a distance to the support, especially with wooden substructures, the less the support surface, the less tension. The lowest distance to a wooden substructure should be at least 30 mm. For example, EPDM bearings..., but this is suboptimal for sufficient ventilation, but there is often no other way.
    
11. In principle, the space for ventilation should be at least 100mm, this can best be designed with adjustable adjustable feet. With adapters, we can also build up to approx. half a meter.
    
12. The ventilation cross-section should be approx. 50% of the side surface and closed with a perforated plate to prevent vermin from nesting. As shown here using the example of our TerraceFix Air.
    
13. The distance between the terrace and rising components should be at least 20 mm, if this is not desired, ventilation can also be ensured by means of gratings.
    
14. The recommended board width depends on the type of wood, native wood boards should not be wider than 120 mm and should be cut rift/half-rift as mentioned. For modified woods, this always depends on the product. The timber trade can provide very detailed advice here. In our experience, tropical woods should not be wider than 100 mm due to the high force development.
    
15. If lateral ventilation is not possible, e.g. with logs, then ventilation should be provided via the decking surface, which is again possible with gratings. The ventilation area can be calculated using the perimeter of the terrace and the installation height.
    
16. Connections at entrances and exits are made in accordance with the sealing and connection standards B3691 and B3692. In addition to the protection of the waterproofing elevations and splash water, this is also about the advantage of ventilation.
    
17. Connections to other components and waterproofing are also regulated in the aforementioned standards and in various HFA publications.
18. Let's take a look at the climate under the terrace. We already know that it is always more humid under the terrace than above, regardless of how often the sun shines on the terrace. The logical conclusion is that the boards are always cupped, regardless of which side of the boards we turn upwards. The underside absorbs moisture and swells, while the top dries out and contracts. This also inevitably leads to screw breakage. You can counteract this by minimizing the contact surfaces.
    
19. The same issue affects us with the width expansion of the planks. The solution to this is a two-part substructure. Two profiles that can slide into each other.
    
20. If you decide on such a system, however, the screw arrangement must again be arranged in a cat's jump, otherwise you block the sliding. This can then look like this: