Rain Splash-up Damage to Wood Siding on buildings InspectAPedia® -
Rain splashback damage to wood siding
Water leakage through building exteriors, cause, cure, prevention
Causes of water damage, rot, insect damage to wood exterior siding
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This article explains the causes & effects of rain splashback or roof spillage splash-up on wood siding, causing rot or insect damage. This article series discusses best practices construction details for building exteriors, including water and air barriers, building flashing products & installation, wood siding material choices & installation, vinyl siding, stucco exteriors, building trim, exterior caulks and sealants, exterior building adhesives, and choices and application of exterior finishes on buildings: paints, stains. This article series includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.
Splashback or splash-up water damage refers to the effects of water on building surfaces when rainwater strikes the ground close to the building. Splashback is most severe in areas where water falling off of a building roof strikes the ground because of the concentration of spillage in such areas. These same conditions are a prime source of building or crawl space water entry troubles. (Also see WATER ENTRY in buildings.)
All building siding products, but especially wood-based products, are vulnerable to discoloration, wear, and deterioration or even wood destroying insect invasion when they are installed close to ground level.
Splashback damage is increased when:
There are no roof gutters installed to intercept and redirect roof runoff
The roof overhang amount is small - that is the roof edge does not extend far past building walls
Wood wall siding is installed close to or even in contact with the ground
Ground slopes towards rather than away from the building
Paving of drives or patios is brought in contact with wood siding
No preservative or protective coating is maintained on the wood surfaces
The building siding is in a shaded or damp area
Photographs below illustrate some of these conditions as well as steps to protect building siding from water damage by roof spillage or splash up.
At below left the combination of modest roof overhang, a natural water trap formed by nearby building walls and retaining wall, and shade were factors in the worn, leaky wood shingle siding on this garage. New asphalt paving was added and sloped to improve drainage out of the area.
At below left, the absence of any roof overhang at all has led to building siding damage. But the generous roof overhang at below-right has worked well to prevent siding damage as well as to keep water well away from the building at a rocky site that could otherwise lead to trouble.
The vertical wood siding at below left was severely damaged from roof spillage and splash-up. The construction of a combination of a concrete entry platform poured against building siding, poor drainage, and spillage from a roof valley make the home at below right an inviting place for carpenter ants and termites.
In wall areas subjected to splashback,
snow buildup, or high moisture from other sources, rubberized
asphalt membranes in widths up to 36 inches can
be used to protect the wall sheathing and structure.
Water
damage from splashback is common in wall sections located
under the eaves of a roof with no gutters. Walls
above decks or flat roofs are also prone to moisture damage
from splashback or snow buildup.
In all cases, make sure to detail the flashing membrane
so that it tucks under the sheathing wrap above and over
the step flashing or cap flashing below. If installed along
the foundation, the membrane should cover the joint
where the sill meets the foundation.
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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John Rudy, Advantage Home Inspections, Flemington N.J. 08822 home inspector, 908-806- 6364, Home, Radon & Termite Inspections, Central & Parts of North New Jersey, email: jonadvantage1@yahoo.com
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