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"Ecological" terraces: aesthetic and durable


Ecological terraces have been trending for a few years, as in general everything that has appeal to the sustainable development of housing. And who says "ecological" implies "ecomaterials", these very low polluting and recyclable building materials, unlike concrete. For ecological terraces, the reference material is wood, which combines aesthetics and durability.

Wood, stronger than concrete

In construction, the direct opponent of concrete is wood. And not only for ecological criteria, but also for reasons of comparable or even better performance for wood. Very largely underused compared to concrete, the latter nevertheless multiplies the advantages compared to its competitor. It is six times lighter, twelve times more insulating, and has double the thermal resistance. The start-up of wood materials elsewhere requires very little water, while being much faster. Finally, in terms of carbon footprint, wood crushes its rival, by storing CO2 and considerably reducing energy costs.

For the realization of terraces, the use of wood and concrete comes up against the same problem: to resist bad weather and water, the number one enemy. For wood, there are 5 classes of moisture resistance. Class 1 does not withstand contact with water, class 2 only tolerates it accidentally. Class 3 can withstand bad weather, but without being in contact with the ground. The last two classes are the most resistant, and logically the most expensive: class 4 does not undergo the alteration of humidity in contact with the ground, and class 5 even tolerates the dreaded salt water. For this last category, the privileged target is of course the seaside and iodized water, capable of ravaging even reinforced concrete in a few years.


Wood species and composite terraces

  To choose the wooden slats forming the terrace, there is a wide choice of species, the price of which varies according to the level of class and the rarity of the wood. To have a somewhat resistant outdoor terrace, it is better to at least choose category 3 wood (but without contact with a loose soil). The most affordable are poplar, Douglas-fir, Landes pine or larch (30 to 35 euros per m²).

For more noble and more resistant species corresponding to categories 4 and 5, prices go up quickly, with around 50 euros per m² for locust, and 80 euros per m² for oak. Exotic woods are even more expensive, combining aesthetics and longevity (rot-proof), such as eucalyptus and jatoba. They also have an extremely high density, which gives them an ultra-powerful natural resistance. However, always with a view to sustainable development, these woods must have labels certifying respect for the use of the original forests. The Forest Stewardship Council (FSC) eco-label is in this case the best known in this area.

Another solution consists in forcing nature's hand, by making the essences of categories 1 to 3 more resistant. There are various techniques for this, consisting of treating the wood or adding preservatives, which must however be of natural origin and certified “CTB P +” (not harmful to man and the environment). For example, “autoclave” wood undergoes heating and is impregnated with preservative elements, in order to protect itself against the action of water, fungi and other parasites.

Finally, there are also “composite” terraces, which mix the use of wood with another material, such as PVC. Very similar in appearance to wood, the boards are extremely resistant, with a lifespan comparable to plastic. In recent years, composite but 100% natural terraces have also been offered, such as “kovalex”. Composed of 70% wood and 30% ecological thermoplastic polymers, kovalex boards do not use PVC while being just as resistant, and guaranteed for 25 years.

The development of wooden terraces and "bioclimatic" pergolas

Although setting up a wooden deck and maintaining it isn't complicated, there are a few things you should know. If wooden slats are the most common elements, it is also possible to use square slabs with a side of 50 cm as for tiles, allowing original assemblies. For the installation, the most important is to respect the wood classes.

Classes 4 and 5 can be in direct contact with the ground, being naturally or artificially protected from rotting. For the other classes, it is possible to place the wooden terraces directly on hard ground (concrete, sand, gravel, clay, etc.), or to raise them to avoid any risk of humidity. In the latter case there are concrete or PVC supports specifically designed for this purpose, on which are placed "joists", long pieces of wood usually used to support a parquet, a floor or here a terrace.

For the most ecological terraces, it is possible to equip them with pergolas, small constructions serving as support for climbing plants, which in summer provide a certain coolness. Used since Antiquity, pergolas have not escaped the ecological wave, since there are now “bioclimatic” pergolas. Built in eco-materials (wood, steel, aluminum), they are potentially waterproof and closed on the sides, providing effective shelter from bad weather.

The most sophisticated pergolas are even clad in technology. Sensors make it possible to detect the first drops from then and to close the roof, made up of parallel pivoting slats. The interior is equipped with lighting, heating, and even speakers, all of which can be operated by remote control. High-tech constructions, which certainly no longer have much to do with their historical reference.

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