How Does a Wood Rain Screen System Work and Why Should I Care?

Even though wood rain screen construction has been around for well over 800 years, it’s only been within the last twenty years or so that builders, designers and property owners have started building with them in North America. They not only look beautiful, but a well-designed wood rain screen can help protect your home and your health. Although all wood rain screens look pretty on the outside, be aware, the performance of each type of rain screen varies significantly. See how.

What’s a Wood Rain Screen?

Basically, it is wood siding that is spaced off the side of the building to create an air gap (wall cavity) behind the siding. That’s where the magic happens. From the outside, the wood siding looks the same and acts the same - it keeps rain and the elements from getting inside your home or building. But the air space created behind the siding provides enough back ventilation to keep the siding dry and helps prevent mold from growing behind the siding.

Got Mold?

We certainly hope not, but if you’re ever seen it in a home or behind the siding on a home, it can be a real horror story. Millions of Americans are affected by mold in their homes. Mold litigation law suits and insurance claims are rampant and currently in the billions of dollars in the US alone. Mold doesn’t just happen in wet and humid areas like Florida and Houston – mold is everywhere. There are claims in Arizona and California and many other arid and semi-arid regions. Mold occurs naturally, but it only grows well where the conditions are right. A wet wall area is a great place for mold to grow. And mold doesn’t just start and stop on the outside - it will work its way inside the structure and wreak havoc throughout a whole home or building. Inside and out, the results can be devastating.

An Ounce of Prevention is Worth a Pound of Cure

It is absolutely true that proper building practices and proper flashing of windows, doors and openings are essential to the long term performance of a building. But a well-designed rain screen system eliminates an essential element for mold to flourish – water. By keeping the entire wall system dry, a properly functioning wood rain screen minimizes the potential for mold and rot – inside and out. Not only is your home or building healthier, it is more structurally sound and adds years to the life cycle of the structure.

Are There Different Types of Rain Screens?

Yes, there are many options and construction techniques to create a wood siding rain screen. Not all rain screens are equal, however. Here's a few rainscreen options.

One simple rain screen option is to place furring strips on the exterior wall and nail wood siding to it. This is somewhat helpful because it does create a wall cavity- but only where the furring strips are not. The furring strips cover roughly 20% of the wall surface. If there is no ventilation for the moisture to escape from behind the wall, though, this system is ineffective because it does not allow the moisture to escape from behind the siding.

Another simple rain screen option is to install furring strips and then use a rain screen fastener to hold the siding in place. If the fastener creates a gap between the siding boards (open joint) which will allow moisture to escape from behind the siding, this will work a little better, but it still does not address the issue of the furring strips blocking out 20% of the exterior wall. Any moisture trapped within or behind the furring strips makes the wall more vulnerable to mold growth.

A third simple rain screen option is to use a ¼” plastic drainage mat behind the wood siding. This is often used with cedar siding and shingles. I believe this is better than no rain screen at all, however it has some limitations, especially when it is not installed properly. It is a closed joint system and if there is no way for the moisture to escape from behind the siding – where’s the benefit? Trapped moisture behind the siding nourishes mold and mold feeds on wood which creates rot.

The best wood cladding rain screen design option is to use an open joint system that requires no wood furring strips. This creates the best design and functionality of all the available wood rain screen options. Eliminating the furring strips has many benefits:

• Saves material costs and labor costs during installation (about $1 - $2 savings per square foot typically)

• Eliminates the 20% blockage of the wall, allowing your home to ventilate more effectively from the inside

• Creates a pressure equalized plane, which allows the siding and the entire wall cavity to dry out quickly

• Creates a longer-lasting, healthier and more effective design, offering long-term life cycle cost savings and minimizes potential mold, damage and maintenance significantly

We hope you enjoyed this article. Please visit MataverdeDecking.com for more information about high performance rain screens, wood siding options and more.