Building with Wood, Building Beautifully, Building to Last

Wood continues to be a key material in construction, and its future looks bright. We can recall that at the last Olympic Games in Paris, it played a major role, with 29.000 m² of wood used, 45% of which was French; the athletes' village alone accounted for 15.000 m², 65% of which was French wood.

Over the past two years, the share of wood in construction has remained stable, with 70% of its use in new housing. Renovation projects have increased in volume, and the share of wood in structural elements has also grown significantly: wood is clearly the obvious choice!

By 2025, national stakeholders had set a target of constructing 8 million square meters of bio-based wood projects, with the aim of increasing the share of French wood to 50% in these constructions.

This 21st-century favorite material offers genuine eco-responsible advantages in terms of durability and insulation, along with aesthetic and warm qualities that make it indispensable. At the same time, it requires best practices to be implemented from the very beginning of a project.

While it does not seem necessary to convince building professionals of the merits of using wood, it is nevertheless important to clarify certain precepts and dispel some misconceptions.

Wood is strong and once it's in place, you're set for a long time!

Absolutely not. Wood is a natural material, but not inert; it changes over time when exposed to the elements. It was a living material before it was cut and retains all its components once processed. It is composed of cellulose, water, and lignin, which will evolve and lead to its degradation over the years if left unattended.

Why does wood degrade?

Cellulose and water are the two elements that exert a significant influence: all wood retains, even after drying following cutting, an incompressible water content, and cellulose, among other things, acts as a water absorber throughout the wood's life. Several behaviors essential to understand and control stem from this hygroscopic characteristic.

What is the impact of humidity on wood?

When used outdoors, in the presence of moisture, wood will absorb water and swell, then shrink during dry periods. These variations will cause cracks or splits in the structure, a phenomenon amplified by frost.
When wood swells, it causes movement in the structure where it is applied: the cladding or decking boards, by "moving" regularly, can weaken and damage the fixings of the structure.

Successive dimensional variations can cause the structure's slats to warp, and they can become dislodged and "come out" of the cladding or terrace.

If the wood turns grey, it's a natural phenomenon, it's not a problem!

This is not true: the lignin present in wood reacts with UV rays, and these rays destroy it, causing discoloration, graying, and degradation of the wood fibers on the surface. Decking or cladding boards are then weakened. And if left without maintenance, this can lead to structural deterioration.

Namely The stronger the sun, the more prematurely the wood will age, that is, whiten, grey, and eventually crack.

External elements are not the only factors impacting the longevity of wood; installation is another essential variable in the equation for the lifespan of a wooden structure.

To limit these natural phenomena and avoid alterations, it is therefore imperative to protect the wood.

It's not a material like any other that you can simply install without care. You have to plan for its protection and maintenance. Otherwise, after two or three years, without protection, the structure risks going from magnificent to dull, grayish, possibly damaged, with an aged, dirty, and neglected appearance.

How do you maintain and protect a wooden structure?

First step to follow: clean

It is essential to work on a clean surface: like the skin of a face. Applying a finish to wood that has been only superficially cleaned or vaguely sanded is like throwing money away, with the risk of having to start all over again.

To clean it, a blast with a high-pressure jet and it's good to go!

Absolutely not: successful maintenance or cleaning begins with understanding the wood:

If the wood is grey, dull and simply dirty, left to the elements: it needs to be cleaned.
If the wood is blackened, deeply soiled with ingrained oils, and has baked in the sun: it must be degreased.
when the surface is covered with an old film-forming finish: it must be stripped

Second step, choosing the protection:

Saturators, as their name suggests, saturate, that is to say they impregnate the wood deeply to protect it durably without risk of peeling.
Oils offer a warm finish but can darken under the effects of UV rays and soil the wood.
Wood stains leave a surface film that resists UV rays well but will tend to flake off over time.

Why have saturators been so popular for the past few decades?

Outdoors, saturator is often the best solution because its impregnation qualities allow the effects of the components to be diffused throughout the structure.

The saturator penetrates the wood and leaves no residue. No surface film, risk of flaking with abrasion is greatly reduced

Its maintenance is simple: the wood is protected from UV rays, moisture, and dirt. Without a surface film, there's no need to strip or sand the wood during maintenance: simply clean/remove the graying (for areas highly exposed to UV rays) and then apply a coat of saturator.

Opinion piece by Jérôme Dauvé, Technical Director of Groupe Durieu (LinkedIn).