Home Inspections: Pressure Treated Lumber, What to Look For!

Home inspectors cite wood to earth contact as a condition that will, eventually, lead to decay of the wood. Sometimes, the wood that is in contact with the soil is pressure treated lumber that is designed for that purpose. This article gives advice on what could be considered appropriate uses for pressure treated lumber.

Wood to earth contact is one of the most frequently cited concerns in a home inspection report. Often, clients ask about wood to earth contact and how it applies to pressure treated lumber. In the world of construction, pressure treated lumber is advertised as having a long life (some say 40 plus years) even with direct earth contact. The manufacturers soak the lumber in chemicals that penetrate into the wood from the outside surface. The most vulnerable area to future rot is where the builder cuts the wood -- such as to length and then that end is dropped in a hole for use as a fence post. In theory, if an end is cut and buried, a topical wood treatment should be applied at the cut. In practice, this lumber does last a very long time. There have been instances of fence posts, that were installed 20 years before, being dug up and they looked as good as they did the day they were buried. On the other hand, depending on soil conditions, sometimes the wood will not meet the advertised expectations for longevity.

Pressure treated lumber, and what a home inspector should say about it when it touches soil, is an issue a home inspector wrestles with. Fact: The wood is manufactured for ground contact, so having it touch the earth is not necessarily a defect. However, pressure treated wood in contact with the soil will last much longer if all soil contact is eliminated. Putting pressure treated lumber on a concrete pier will make it last longer.
A logical means of evaluating the situation, that makes sense for the home inspector, follows: If pressure treated lumber is being used in a crucial role, and it is in contact with soil, then the inspector recommends removal of the soil. For example, if a structural post under the house is buried the risk for extensive damage, the result of rot, cannot be ignored. Another example: Outside columns that support high decks should be kept well away from soil. High decks can come down if the columns rot.

Now, if an inspector finds a couple pressure treated 4x4's, for support of a handrail, sunk into the earth at the steps from a low deck, that is a relatively minor concern. Usually the inspector will probe the lumber at the ground level and, if it is sound, not think or say much about it. No grading is applicable, since the posts are sunk into the ground, in part to make the rail steady. Pressure treated lumber is commonly used in simple outdoor applications and, down the road, any repair should be simple to do and the area easy to access. Should there be a problem at some point, a workman who is affordable can perform the repair and no structural damage is likely to have occurred. That makes this an appropriate use of pressure treated lumber.

This article was produced by the writing team of Eric Badgley; specializing in Sudden Valley Real Estate and Bellingham Real Estate.