Composite Wood Siding: A Home Inspection Checklist

In recent blog posts, we’ve discussed the importance of never waiving a home inspection—a critical mistake many homebuyers are making to gain a supposed advantage over competing bidders in this sellers’ market. What may seem like a savvy move to secure the property at an “as is” price, in many cases, has proved to be a costly blunder for homebuyers. That’s because the cost of replacing aging systems—that would have been highlighted in a home inspection report—often significantly outweighs any savings from foregoing a home inspection.

Let’s take exterior siding as an example. Depending on the type of material, part of the country, the scope of the job, and labor costs, replacing a home’s siding can be one of the more wallet-busting upgrades facing a homeowner. Unless you have $10,000 to risk (less in some cases, much more in others), you’ll certainly want to reconsider skipping the home inspection before signing on the bottom line.

One of the more problematic types of siding is composite wood and hardboard. These engineered wood products, such as oriented strand board (OSB), have a well-documented history of being prone to critical moisture-related damage (often around fasteners and seams), as well as installation problems. This is particularly true of early composite wood installations done prior to 1996. For example, some OSB products, created from flakes and wood strands glued together to resemble genuine wood, have been the subject of class-action lawsuits resulting from the product’s inherent flaws—most notably its ability to retain water.

Here is a checklist of composite wood siding problems found by the home inspectors at A-Pro over the last 27 years:

Water Issues: Rain and melting snow are the biggest enemies of composite wood siding. Your inspector will note problems such as panels that have swelled, warped, blistered, buckled, or rotted. Some defects will be obvious, such as severely decaying wood, while others may escape the eye of a homeowner, such as boards that have swelled from moisture absorption. Surface cracks will also be reported since they invite more water into the panel, accelerating further damage. As many unhappy homeowners discover, once moisture gets behind the panels, you’re looking at serious repairs which may include fixing structural damage. Other indicators of moisture problems include water staining and rusted nails.

Organisms: The presence of fungi and bacteria, even on a few panels, is the reason for concern. If not addressed, it will spread and cause widespread damage, turning the solid wood product into a spongy mess and possibly necessitating a complete siding replacement.

Poor Installation: There are a number of issues that can result from the amateurish installation of composite wood siding. These include failure to caulk exposed nails (which must be the galvanized type); not leaving gaps between adjacent boards to allow for natural expansion of the wood; completing the installation without properly sealing drip edges; leaving panels exposed to damage by not sufficiently painting with a preferred covering and in more than one coat; letting panels touch masonry; and not leaving the recommended clearance between the siding and the roof. In some cases, incorrect board spacing that doesn’t allow panels to breathe will lead to buckling. The inspector will also point out the absence of door and window flashing designed to drain water away from the siding.

It must be mentioned that while the installer may be primarily at fault—in addition to factors such as age and climate—homeowners who are not vigilant about proper maintenance share some of the blame for siding that is beyond repair. Negative ground slope and clogged gutters, for example, can cause water to pool and rot to occur, and sprinklers trained at the siding won’t help keep it in top shape, either.

Hardboard: Many of the same issues with OSB can also be found in pressboard/hardboard siding, which hasn’t been manufactured for the last couple of decades—a problem for homeowners searching for matching material to repair damaged panels.

A complete assessment of a home’s siding is part of A-Pro’s 500-point home inspection. Ask your local A-Pro Home Inspection team about its complete foundation-to-roof inspection in Boulder. To schedule one, call 1-720-438-4595 or visit the link below.