Inspecting Lower Levels For WDIs

For unfinished basements and crawlspaces, PMPs need a plan.


Editor’s Note: This article was reprinted with permission from Techletter.


The unfinished lower levels of a home can include basements, crawlspaces, cellars, and any room without sheetrock, paneling, and other materials covering walls, ceilings and floors.


When you are inspecting for subterranean termites or other wood-infesting pests, you are most likely to find evidence in these lower level spaces because: (1) below-ground floors are more likely to have moisture problems, (2) subterranean termites most often invade from soil below and infest lower levels first and (3) unfinished areas provide you with the easiest access to thoroughly inspect exposed high-risk areas such as floor joists, wall studs and sill plates. Here you are able to probe and sound wood without risking cosmetic damage.


INSPECTION PLAN. Unfinished lower levels may give you the best chance of finding wood-infesting pests so be thorough when inspecting. Just as when you conduct an exterior inspection, develop a system for inspecting unfinished basements and crawlspaces and follow it every time so that you avoid the risk of missing some key area or element of construction.


For example, you might always start by checking the wood trim at the entrance and then proceeding systematically along the foundation walls, around piers, underneath bathrooms, etc., all the while looking carefully for termite tubes, sawdust, frass piles, emergence holes in wood, or evidence of mold or mildew. Inspect interior walls, support pillars, pipes, chimney bases and anything else coming out of the ground. Make sure you check all accessible areas and make note in your report of areas that were not accessible. Crawlspaces can be large and meandering; you may need to go back and forth to reach all areas. Termite galleries can be hidden in the most solid-looking sill, and powderpost beetles in the furthest joist from the entry.


Think safety first when inspecting any unfinished area with exposed beams or pipes, dangling electrical wires or loose insulation. There are even possible animal threats, such as black widow spiders or snakes. Wear gloves, head protection and other PPE when needed.


MOISTURE ISSUES. The following are signs of moisture issues in crawlspaces and basements:


    • Standing water
    • Musty, damp smell
    • Damp foundation walls
    • Wood decay (fruiting bodies, white cottony growths, brown crumbly wood, bleached and spongy wood)
    • Efflorescence (white or grey “ash” on foundation walls from salt deposits left behind by evaporating water)
    • Water stains, mold stains or mildew on joints, subflooring, sills and foundation walls
    • Spalling (flaking or peeling block or brick from water immersion)


PRIME INSPECTION SITES. When you’re in lower levels, the following are spots you do not want to miss when performing an inspection:

Sill plate area — The sill sits directly on top of the foundation wall and supports the house above it. There are different types of sills but all are commonly infested by subterranean termites. Probe the wood and look for termite tubes in crevices.

Joists and headers — Look for termite tubes (including drop tubes). Sound and probe wood and use a moisture meter to spot check for wood with a moisture level higher than 20 percent.

Wood buried or embedded — Posts for wooden stairs in older homes may rest on, or be embedded in, concrete. Wooden support posts for the floor above, door casings/frames and partition walls may be imbedded. Highest risk is a wood support that rests on a footer below the soil surface, providing direct and hidden access for subterranean termites.

Wood elements attached to foundation wall — Wooden cabinets or shelf systems may be installed directly on block foundation walls. You may find wood furring strips that have been installed to hang pegboard or other items. Termites commonly attack this wood through holes and cracks in the block wall.

Wood framing in windows and window wells — Look for termite tubes around and behind wood framing on windows. Also look for termite reproductive or detached wings near windows, as well as cracks in the block wall.

Other lower level sites that should be checked are: the area behind dirt-filled porches; subflooring beneath kitchens and bathrooms where water may have leaked (use a moisture meter); HVAC and water systems (water heater, pressure tank, cistern) that may leak or generate condensation; sump pits or French drains (remove pit cover and check for termite tubes); and block or brick that shows cracks, damage to mortar, discoloration or other evidence of moisture problems.

The authors are well-known industry consultants and owners of Pinto & Associates.

January 2021
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