Wood as a facade cladding material is a construction solution increasingly used in architectural projects. Grupo GUBIA demystifies the use of this material in these applications and highlights it as a sustainable, efficient and durable alternative. Paseo de Mallorca 15 and Parallel East&West in La Bonanova are the last two projects with wooden facade in which GUBIA has been working.
Wood construction is an increasingly growing trend and, specifically, wooden facades are a sustainable, aesthetic and versatile option that more and more architects and designers are incorporating into their projects. Grupo GUBIA, a Sevillian studio specialized in the design and construction of spaces with wood and bamboo, has seen in recent years how its demand has increased in this regard and, thanks to its technical team and experts, has already developed different solutions of wooden facades for other architectural studios or developers.
Two of the latest projects in which GUBIA has been involved are Paseo de Mallorca 15 and Parallel East&West in the neighborhood of La Bonanova, both in collaboration with the architectural firm OHLAB.
Projects with wooden facade
The first of these is a residential complex of seven floors high. It is located on Palma de Mallorca’s golden mile and designed according to Passivhaus standards. A skin of thermo-treated wood, consisting of fixed and sliding panels of vertical slats, covers almost the entire building. This element becomes the solar filter for the apartments.
The second, in the same city, are two buildings composed of six duplexes each.The north and south facades of both are again the protagonists of the project, incorporating a motorized folding lattice system, also made of thermo-treated wood. The wooden slats, in this case placed horizontally, again work in favor of the solar control of each dwelling.
In both cases, Grupo GUBIA, chosen by architects for its expertise and know-how in the field, has developed and executed its unique wooden facades. These elements have sliding and vertical folding movements respectively, which bring dynamism and vibration to a changing façade image. With their usual method, the team has carried out a detailed study of what they consider to be the six keys to designing a wooden façade.
Use class
First of all, as Verónica Sancho, chief architect of Grupo GUBIA points out, “it is essential to identify the type of use of the wood element in question that is going to be designed. That is to say, to identify the exposure to water that the wood element is going to have throughout its useful life”. The Technical Code DB-SE-M 3.2.1.2 and the UNE EN 335:2013 standard recognize two subclasses, 3.1 and 3.2, depending on whether the construction design facilitates water drainage and thus the drying of the wood or, on the contrary, whether the wood can remain damp.
Durability
Then, Sancho explains, “we will have to choose a wood species with high durability, _between values 1 and 2 for that class of use_, given that the useful life of this material depends on the humidity to which it is exposed. This exposure favors the attack of different xylophagous agents, such as fungi, coleoptera, termites… In general, tropical woods such as iroko, ipé, teak or cumaru have a very high natural durability. However, coniferous woods with specific internal modification treatments, physical such as heat treatment or chemical such as acetylation, are completely suitable for these uses”.
This type of modified wood generally has very small expansion and contraction movements. They constitute very stable materials that make it possible to achieve slender and elegant sections or pieces, thus improving the aesthetics and designs of the wooden façade. ” Thermo-treated bamboo is also an excellent alternative,” emphasizes GUBIA’s chief architect.
Constructive design
And precisely because water and humidity are the greatest enemies of exterior wood, designing the construction details of a wood facade correctly is the next step in the design process.
It is always necessary to facilitate the evacuation of water, to prevent it from accumulating. As recommended by the architect, this is achieved, for example, by rounding the edges of the pieces, inclining the surfaces. Also, avoiding concave surfaces, eliminating joints between different pieces that can retain water. And she continues, “it is essential to know how the material behaves, the contraction and expansion movements inherent to any wood will vary depending on the relative humidity to which it is subjected, especially outdoors.
We cannot restrict their movements, our construction detail must contemplate and facilitate them. This will avoid the appearance of cracks that will contribute to water retention. It is also essential to favor the ventilation of the air chamber behind an exterior wood cladding. It is also important to pay attention to the quality of the fasteners that can react with the wood, creating unaesthetic stains on our facade.
An ideal design of any wooden facade will also contemplate an easy and quick replacement of its parts. This is because it is possible that some of the wooden elements exposed to the exterior may suffer slight damage. For these situations, GUBIA’s technical department has developed multiple hidden fastening elements that facilitate their assembly and disassembly.
“It is also necessary to highlight,” emphasizes Verónica Sancho, “the importance of choosing the right finish, the correct installation and commissioning of the façade elements and, of course, the subsequent maintenance service.”
Finish
As for the first thing (the finish), it is to protect the wood from the effects of the sun. Over time, untreated wood will lose its color and turn gray. “There is a wide variety of exterior wood finishes on the market. However, it is difficult for a supplier to guarantee the durability of the finish over time. The confinement allowed us to research, try and test numerous national and foreign products and choose the one that gave us the best results. Laboratory tests, outdoor exposure tests and a long etcetera made us opt for a protective cream in these last two projects. This product is easy to maintain and waterproofs the material to repel water,” says Sancho.
Installation and maintenance
To ensure that a wooden facade works, it is also necessary to have a correct installation carried out by professionals, experts who know how to foresee and remedy the possible irregularities that occur in any work. “Our carpenters know very well how wood behaves, they know how to recognize when a support can give problems and how to solve them, and that is fundamental. An excellent construction detail on paper is of no use if it is not correctly put into practice. Paper supports everything, but the reality of the works is different”.
Finally, says the expert: “the maintenance of exterior wood is key for our facade to last as the first day”. This implies making the end customer aware that wood requires certain maintenance periods that will depend on the orientation of the facade, the relative humidity of the climatic zone in question, the tone of the chosen finish… According to him, it is not possible to extrapolate maintenance to any building without studying all these factors.
And only in this way, she points out, “taking into account each and every one of these points, will we be able to achieve a facade that lasts over time, a facade that is a success”. “In Grupo GUBIA we want to dismantle the many myths that exist about wood used in exteriors,” Sancho concludes.
