sheathing rot

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Open-Cell Spray Foam and Damp Roof Sheathing

When open-cell spray foam insulation is installed on the underside of OSB roof sheathing, the sheathing sometimes gets damp

Posted on Jan 3 2014 by Martin Holladay

UPDATED on July 8, 2015

Now that insulation contractors have been installing spray foam insulation on the underside of roof sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. for several years, we’re beginning to accumulate anecdotes and data on successful installations and failed installations. The anecdotes and data are enough to provide a few rules of thumb for designers and builders who want to install spray foam on the underside of roof sheathing.


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Image Credits:

  1. Mark Parlee
  2. William Miller, Andre Desjarlais, and Marc LaFrance
  3. Simon Pallin, Manfred Kehrer, and William Miller

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All About Wall Rot

If your wall sheathing is rotten, the first question to answer is: where did the moisture come from?

Posted on Nov 23 2012 by Martin Holladay

Contractors who specialize in repairing rotten walls won’t run out of work any time soon. The epidemic of wall-rot problems that began more than 20 years ago shows no signs of abating. In fact, wet-wall specialists are often called to investigate problems in developments where most of the homes have rotting walls — and in some cases, these homes are only six years old.


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Image Credits:

  1. Photo with pipe staging: Will Smith — Rot under window: Mark Parlee (MP) — Splashback: Fairhope Farm — No kickout: MP — Missing step flashing: MP — Missing deck flashing: Everflashing — Ice dam: Ecduzitgood — Solar vapor drive: MP — Exfiltration: FHB

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How Risky Is Cold OSB Wall Sheathing?

The thicker your wall, the colder your sheathing. If you build a very thick wall, will your sheathing stay cold and wet?

Posted on Nov 5 2010 by Martin Holladay

During the winter months, wall sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. is usually cold. Cold sheathing is risky, since it tends to accumulate moisture during the winter. Unless the sheathing can dry out during the summer months, damp sheathing can rot.


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Image Credits:

  1. GreenBuildingAdvisor

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