Water-resistive barrier
A water-resistive barrier is the layer behind cladding that sheds any water that gets past the exterior face and directs it out of the wall.
A water-resistive barrier is the layer behind cladding that sheds any water that gets past the exterior face and directs it out of the wall.
Definition
A water-resistive barrier, often shortened to WRB, is a material behind the exterior cladding that protects the wall structure from liquid water that gets past the outer face. It is lapped to drain water downward and out.
A plain example
On a framed wall, sheathing is covered with a WRB sheet or coating, laps shingled from bottom to top, and flashing integrated at windows and the base. Water that gets behind the cladding then runs down the barrier and exits at the flashing.
Why it matters
No cladding is perfectly watertight, so the layer behind it is the backup. Water damage inside walls is slow, hidden and costly, which is why laps, tape and window integration are inspected before the cladding goes on.
Common confusion
A WRB is not automatically an air barrier or a vapor retarder, even if some products combine functions. Check what the product is listed for. It is also not a substitute for flashing, which handles water at openings and terminations.
On a project
Check the lap direction, the tape and the integration with window flashing before cladding goes on. Take photographs of the barrier before it is covered, as a record for later.
Quick answers
- Why shingle the laps? So water that gets behind the cladding flows over each lap and out, instead of into the wall.
- Is a WRB the same as house wrap? House wrap is one common type of WRB. Coatings and boards can also serve the role.
- What must a WRB comply with? Local code and the product listing. Confirm with the designer and local authority.
Related terms
Always check the project drawings and specification, and confirm requirements with the engineer of record and the local authority.
Questions people ask
Why shingle the laps?
So water that gets behind the cladding flows over each lap and out, instead of into the wall.
Is a WRB the same as house wrap?
House wrap is one common type of WRB. Coatings and boards can also serve the role.
What must a WRB comply with?
Local code and the product listing. Confirm with the designer and local authority.
Sources and further reading
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