Another culprit that leads to beam damage is the installation of improper beam caps—those thin, galvanized metal coverings that are meant to protect the beam from water exposure.
"If homeowners or an inexperienced handyman put on a metal beam cap in the wrong style, it can actually accelerate the rot process," Larson says. "I have metal caps especially made for these beams, so that water is always diverted away when it hits the top."
Dry rot in Eichler atrium beams should be addressed early. There, dry rot that extends into a roof beam can spread into the adjacent framing and cause the structure to collapse under the weight of the roof. Damaged beams in a carport are also serious because they involve load-bearing support.
Beams are designed like a human backbone; each beam, or vertebrae, has a specific purpose. If you modify or change the beam, you are compromising the integrity of the structure.
"I have not seen a catastrophic failure, but sometimes I find myself blocking and bracing a beam when I get to a house, because they look like they could be really bad," Larson says. "Once water gets into a beam, it can run through it, and run into the house and down the wall."
Experts say you can repair up to 20 percent of a beam's structure before replacement becomes the only viable option.
For a do-it-yourselfer to repair surface damage (up to one-half inch deep), use a spackling paste before sanding, priming, and repainting with a quality exterior paint.
For deeper damage, use an epoxy filler (such as Restor-it), available at better paint and hardware stores for around $25. "It's extremely nasty to work with, but a really good product," Larson says.
Sometimes, however, by the time you begin to see warning signs, some level of beam replacement might become your only option. If you're lucky, only a top or end of the beam will need replacement, but extensive damage will require the entire beam to be removed and replaced.
But our experts agree: you can't just go to Home Depot or a common lumberyard and pick up headers; you need aged lumber that won't twist, warp, or split.