Siding materials need proper clearances between finish grade and the siding—regardless the type of siding.
This requirement is not just to prevent damage to the siding—–it serves a couple of other functions as well. Maintaining proper clearances reduces access to wood structures behind the siding by wood destroying insects or damage from water that might find its way behind the siding.
It allows for inspection of the area. In other words inspectors can see what type of foundation is there, whether flashings are there and whether insects are moving into the structure behind the siding.
It is likely that in all parts of the country there is some reason to follow these principles—-not just the wet North West—and this is reflected in the building codes.
I have had builders tell me that if the siding can’t be damaged by water, that there is no problem with bringing the siding right down to the ground. While it is possible to design a wall cladding that could get away with this approach—–as a general rule it is not a good idea, and proper clearances are required. At an inspection a while ago, I was fortunate to get perhaps the most perfect example of why the builder’s logic is not sound.
Take a look at the concrete patio in the following picture. Notice how the patio is poured right up to the house and the siding comes right down to the patio. This in vinyl siding and is in no danger of being damaged by water. However, as an inspector I can not tell what is behind this connection. Flashings? Concrete? Treated wood? Untreated wood?
The point is—-who knows?
Of course sliding my knife under the siding at the concrete I didn’t hit anything. Whoops—this is not going to be good, I thought to myself.
This next picture was taken in the crawl space. The entire rim joist was bug infested and rotted away over the whole length of the patio connection with the house.
The grey color visible in the picture is the back side of the vinyl siding.
Maintaining good clearances between finish-grade and siding materials of all kinds is crucial to preventing this kind of damage. In most cases it doesn’t make any difference whether the siding is wood, vinyl, aluminum, stucco or brick.
Of course, creating proper clearances may require creating proper foundations first.
Charles Buell, Real Estate Inspections in Seattle
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