Do wooden louvers really deteriorate? The answer provided by Takatsuki Castle Park Arts & Culture Theater

Lately, every time I see wooden louver exteriors, I have a thought.

"What will happen to this in 10 years?"

I strongly feel that the criticism against using wood for exterior walls is growing.

Maintainability, weather resistance, and responsibility as a public building.

Even when I propose it as a designer, it is not uncommon for the facility side to reject it.

When I visited the Takatsuki Castle Park Arts & Culture Theater,
those anxieties were carefully resolved one by one.

First, how is general wood protection handled?

What is commonly used as a protective material for exterior wood is
wood protective paint (WP).
It creates a film on the surface to protect the wood from rainwater and ultraviolet rays.

But it is different here.

They are dip-treated in liquid glass.

This is a technology that allows the material to penetrate the wood and form a glass coating at room temperature. By having the protective material enter not just the surface but the interior of the wood as well, it protects areas that cannot be reached by WP.

And this is the crucial part: even the holes for the drift pins used for fixing are dip-treated.

Usually, when you screw things together on-site, corrosion starts from those screw holes. Even if the surface of the wood is protected, the cross-section of the hole is defenseless. Here, everything including the drift pin holes is dip-treated at the factory processing stage, so there is no starting point for corrosion.

The installation method is also thorough.

The fixing method involves inserting the louver into a U-shaped metal fitting and inserting a drift pin from the side.

Wood shrinks when it dries.
With screw fastening, it becomes loose when the wood shrinks.
But with this method, even if it becomes loose, the drift pin prevents it from falling out.

Moreover, there is no on-site processing at all. Everything is handled at the factory.

Design and maintenance are considered simultaneously.

The louvers are laid out to be uneven.
This is not just to create a rhythmic design.
Even if the surface is planed down in the future, the unevenness prevents it from looking unsightly.
In other words, they have achieved a 'chiri' (offset) through the unevenness of the louvers.
Maintenance is woven in from the time of completion.

For louvers covering glass surfaces, there is even consideration to widen the pitch more than usual so that hands can reach in for cleaning.

Glass copings are installed on the top edges of the louvers. This protects the end grain from rainwater without compromising the design.

And they use up every piece of wood.

They differentiate the parts taken from a single tree, such as heartwood, core material, and sapwood,
between the interior and exterior.

Even if the surface of the wood becomes weathered and can no longer be used as exterior material, it is also intended to be recycled as park benches or furniture.
Furniture using louver material was already installed inside the facility.

Use up every piece of wood.
That determination resides in every detail of this architecture.

Thoughts as a designer

The anxiety about using wood for exterior walls is not unfounded.
But seeing Takatsuki, I was convinced.
The problem is not the material of wood, but the designer's determination regarding how far they will engage with the wood.

As a natural material, deterioration is unavoidable, but
delaying deterioration, considering maintenance and renewal, and utilizing it.
I was impressed by how far they went.

Facility: Takatsuki Castle Park Arts & Culture Theater
Design: Nikken Sekkei