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Water damage to building walls from rain splash: this article explains the causes & effects of rain splashback or roof spillage splash-up on wood siding, causing rot or insect damage.
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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.Also see WOOD SIDING FLASHING DETAILS and also FLASHING WALL DETAILS.
Adapted/paraphrased with permission from Best Practices Guide to Residential Construction. Steven Bliss.
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:
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 right, the absence of any roof overhang at all has led to building siding damage. But the generous roof overhang at below-left 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.
Other Sources of Water Splash-Damage to Building Exterior Walls: lawn sprinkler & lawn irrigation systems
Exterior walls are also vulnerable to damage from recurrent wetting from lawn sprinkler systems and some irrigation systems, and rarely, from the spray of aboveground disposal of septic effluent (not normally discharged close to a building). Even if originally it was properly set, a mis-adjusted lawn sprinkling system or irrigation system spray head, perhaps struck by a mower or other event, may become turned so as to soak the building;
Our underground lawn sprinkler photo at above left illustrates the sprinkler head of a typical buried lawn sprinkling or lawn irrigation system. This lawn sprinkler is located at a home in Tucson, AZ and was well away from the building wall. Lawn sprinkler heads located close to the building wall (photo at above right) must be adjusted to spray only away from the building.
We have also found wall damage such as algae growth, rot, and fungal infection of wood-clad walls and some stucco-covered walls due to splashing from simpler lawn sprinklers placed more distant from the building but whose spray or cyclic spray soaks the building wall.
Watch out: beyond cosmetic damage, recurrent soaking of a building exterior wall, especially wood or stucco-over-wood walls, there is risk of rot, insect attack, and mold growth inside the wall cavity.
Splashback Damage Protection for buildings
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.
Also see FLASHING WALL DETAILS,
-- Adapted with permission from Best Practices Guide to Residential Construction.
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Frequently Asked Questions (FAQs)
Can you help me find an article to confirm what we have been telling our neighbor? We have repaired our side of cinder block based stucco wall by restucco and painting twice. It is deteriorating on our side due to water. We live in las vegas,NV. Their property is higher than ours. Their bushes and plants are being watered by an irrigation system. We have tried telling them that water always chooses the lower route. We've had a gardener tell us that no shrubs should be planted within three feet of wall to prevent this problem. Their raised beds further down the wall is causing the same problem. Since there property is higher, there is no damage to their side of the wall. They say it is our sprinkler system over three feet away from our side of the wall that is causing the problem. Can you direct me to any articles that can help explain this problem to them? - Anon. Sept 2013
'd like to help but need a more clear and confident idea what's going on. Perhaps some photos would help; Typically a stucco wall is likely to be damaged if it is actually being sprayed by water - say by a sprinkler system or from roof spillage; If you want to argue that your wall is damaged by wet soils around the wall, and if you do not have your own sprinkler system outside that wall, it should be possible to photo document and measure-document the soil wetness when the neighbor's watering system has been running for some time. That would suggest cause and effect; I wouldn't expect stucco damage high on the wall in that case. Some examples of walls damaged by water splash are shown in the article above.
Questions & answers or comments about the damage caused by rain splash-back on building walls & other building components.
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