How to Repair Water-Damaged Siding
Replace water-damaged siding with fiber cement
I've had plenty of phone calls over the years from homeowners who are convinced they have to reside their entire house because some of their siding has been damaged by water. Yet when we take a look at these jobs, we often find that relatively little siding has to be replaced. Even better, the homeowners are surprised to learn that the fiber-cement siding we use as a replacement is often a perfect match for what they have. What's more, it resists damage from water and insects. What causes water damage? We get significant rainfall along the Gulf Coast where I live, and that leads to a lot of siding problems. But even in dryer parts of the country, lawn sprinklers that routinely wet siding or shrubs growing too close to the house to allow sufficient air circulation also lead to damaged siding. Most of the problems we see involve hardboard siding because it is so common here, and it's not always installed correctly. Carpenters might have overdriven the nails, improperly sealed joints or allowed cut edges to come too close to the ground. Over time, rain runoff soaks into the siding and causes mildew and rot. By the time the homeowners notice the siding is soft, they've got a real problem on their hands. The good news is that damage is usually limited to two areas: the first three courses of siding (2 feet or so up from the ground), and wood-framed chimneys, or chases, that aren't protected by a roof overhang. Where the siding has been installed properly, and where it's not soaked by rain, it's usually fine. We tear off the damaged hardboard and replace it with fiber-cement siding. The sheathing and framing sometimes need repairs too, but that is less common. In most cases, the original layer of building paper or housewrap at the bottom of the wall was enough to prevent water infiltration and damage beneath the siding. The repair is simple if you follow the details in the illustration above. The wood-grain pattern on the fiber-cement siding is often a perfect match with existing hardboard, although it's not as good a match with real rough-sawn wood. When the new siding has been painted — two coats of top-quality acrylic latex over a primer — the repair is hard to spot. Another plus is that fiber-cement can be brought closer to the ground than the 8-inch minimum I give hardboard. Several brands of fiber-cement siding are available; we're most familiar with Hardi-plank from James Hardie Building Products. The siding, made from portland cement, sand, cellulose and other additives, is available with smooth or simulated wood-grain finishes. Planks are 12 feet long x 5/16 inches thick., and they come in a half dozen widths, which means weather exposures can vary from 4 inches to 10 3/4 inches. Though it used to be a little more expensive than hardboard siding, fiber-cement siding now costs less in my area. Hardboard siding 8 inch wide costs 45 cents per linear foot, while fiber-cement runs 37 cents. There's one more thing homeowners like about fiber-cement siding: It holds paint better than wood. One house I worked on still looks great after eight years. Around here, most people start thinking about repainting after only three or four years.