Wet Climate? Protect Your Investment with a Rainscreen System
Throughout history builders have had to cope with moisture and how it can impact the built environment. Materials interact with moisture in innumerable ways, and architects, engineers, and builders must tailor mitigation strategies to their customers' needs and the building environment. Increasingly, specifiers are looking to rainscreen systems that utilize natural wood products to address moisture control.
"The concept of a rainscreen is not new," says Brian Lotz, Director of Business Development/Outside Sales of Timber Holdings USA (marketer of the brand name Iron Woods®) in Bedford, New Hampshire. "The Vikings used the concept of an open wall rainscreen system back in the 12th century."
A rainscreen is a siding installation that establishes an air gap between the siding and a water-resistive barrier. This open system allows moisture to enter the system but also allows it to evaporate naturally.
In wood rainscreen systems, wood board faces are screwed to traditional wood battens. The wood selections are all durable and sustainable exotic and lesser known wood species.
Spotlight On: Garapa, Brazilian Ash
Species: Apuleia leiocarpa
Origin: South America
Common Applications: Exterior joinery, flooring, stairs, decking, dock and boatbuilding.
Characteristics/Appearance: Garapa is a fine grained wood with a light yellow to warm golden brown hue and darkens with age. It has a fine straight-grained, interlocked medium texture. This wood is fairly easy to work, despite its density. It glues easily and is very stable once glued. It saws, nails, and screws well with little to no blunting effect on tools.
Janka Hardness Scale: 1,650 lb_f (see chart on page 19)
Comments: Garapa is naturally water-resistant, less vulnerable to insects, rot and decay. With an excellent durability and a high resistance to daily wear, it has a long lifespan of 25 years or more. Garapa also features a Class A fire rating.
Spotlight On: Massaranduba, Bulletwood
Species: Manilkara bidentata
Origin: Caribbean, Central and South America
Common Applications: Decking, flooring, boatbuilding, turned objects, and heavy construction.
Characteristics/Appearance: Massaranduba has a medium dark heartwood color, with pale yellow sapwood. The grain is straight to interlocked or wavy, with a fine uniform texture and a low natural luster. It responds well to steam bending. The high density and oil content can be a challenge in gluing.
Janka Hardness Scale: 3,130 lb_f (see chart on page 19)
Comments: Massaranduba is one of the most beautiful hardwoods in the world. It is well known for its high density in heavy load construction projects and good durability in exterior applications. Despite its high density, it generally produces good results with both hand and machine tools. It does exhibit an above-average dulling effect on cutters.
Frequently asked questions
How does a wood rainscreen siding system control moisture?+
A rainscreen is a siding installation that creates an air gap between the siding and a water-resistive barrier. This open system allows moisture to enter but also allows it to evaporate naturally. In wood rainscreen systems, wood board faces are screwed to traditional wood battens.
How far back does the rainscreen concept date, according to Brian Lotz of Timber Holdings USA?+
According to Brian Lotz, Director of Business Development/Outside Sales of Timber Holdings USA, the rainscreen concept is not new. He notes that the Vikings used the concept of an open wall rainscreen system back in the 12th century.
Why is Garapa (Brazilian Ash) a good choice for exterior rainscreen applications?+
Garapa is naturally water-resistant and less vulnerable to insects, rot and decay. It offers excellent durability, high resistance to daily wear, a lifespan of 25 years or more, and carries a Class A fire rating.
What are the workability characteristics of Garapa wood?+
Despite its density, Garapa is fairly easy to work. It glues easily and remains very stable once glued, and it saws, nails, and screws well with little to no blunting effect on tools.
What makes Massaranduba (Bulletwood) suited to heavy construction and exterior use?+
Massaranduba has a Janka hardness of 3,130 lb_f and is well known for its high density in heavy load construction projects and good durability in exterior applications. It also responds well to steam bending, though its high density and oil content can make gluing challenging.
What tool considerations should builders keep in mind when working with Massaranduba?+
Despite its high density, Massaranduba generally produces good results with both hand and machine tools. However, it does exhibit an above-average dulling effect on cutters.