Rainscreens - Behind the Scenes Details
The layers behind your exterior cladding are just as crucial as the cladding itself—if not more—because of how they work while remaining hidden from view. No siding is completely waterproof; even brick and stone allow moisture to penetrate. Instead of striving for an impossible goal of keeping all water out, building scientists and cladding manufacturers have developed wall assemblies that let water enter and escape without damaging the cladding or the home. These systems go by different names depending on the region, but for this article, we will refer to them as rainscreens.
How is it constructed?
A rainscreen's primary function is to create a drainage plane that allows water to exit the wall assembly safely. It consists of four main components:
Structural Wall Sheathing – Typically made of 7/16” oriented strand board (OSB), this layer is nailed to the wall studs to maintain the wall’s structural integrity.
Water-Resistive Barrier (WRB) – A membrane or material, such as house wrap or rigid insulation, that shields the wall sheathing from moisture. The WRB is fastened to sheathing, and the seams and joints are taped with construction tap. Doors are windows are flashed into this layer like a shingle to allow water to escape through the weep holes.
Drainage Plane – An air space between the WRB and the siding, enabling water to drain through weep holes at the bottom of the wall. The depth of the airspace can vary from nothing (for vinyl siding) to 1”, for wood siding and stone.
Cladding – The visible outer layer of the home’s exterior, from vinyl siding to brick or stone.
Different Rainscreens for Different Cladding Types
Different types of siding require different rainscreen systems. Brick is installed 1” away from the wall, with weep holes at the bottom to allow drainage. Vinyl siding naturally provides its own rainscreen due to its design, which allows water to drain through built-in gaps. However, for materials like wood, engineered wood, and fiber cement siding, proper rainscreen construction is essential. Ventilation plays a vital role in preventing moisture-related problems and the airspace promotes drying on both sides of the cladding.
The rainscreen is built using 1x3 or 1x4 wooden strapping, ¾” to 1” thick, installed over the WRB. The configuration of the strapping depends on the siding orientation:
- Horizontal Siding Installation – Strapping is placed vertically, aligned with the wall studs, to create drainage pathways.
- Vertical Siding Installation – An additional horizontal layer of strapping is added over the vertical strapping to support the siding and maintain airflow.
Heavier siding materials also have specific fastening requirements. In regions like the Ottawa Valley, building codes often mandate at least 1” of rigid exterior insulation. As a result, the rainscreen must not only allow for drainage and ventilation but also provide sufficient structural support for attaching the siding. To meet these requirements, the thickness of the strapping is adjusted accordingly, with 1” thick strapping used where necessary.
Essential for Performance & Warranty
At Quality Homes & Renovations we pride ourselves on following the manufacturers’ installation guidelines and best practice. This ensures not only that your cladding will perform and look its best for years to come, but covers the material under the manufacturer’s warranty. The research and education are done beforehand to ensure the correct materials are ready for the installation, and our crew members follow the guidelines exactly. We encourage you to educate yourself as well and are happy to walk you through the fine details and answer any questions.
By choosing the right rainscreen for your cladding, you will significantly improve their siding’s durability and performance and meet the manufacturers requirements for warranty. Reach out to Quality Homes & Renovations for your exterior renovation projects.
