DIY: Repair, Don’t Replace, Rotten Wood

Photo: akeg/flickrWood anywhere in your home is vulnerable to decay in the form of wet or dry rot. A rotten wooden door, floorboard, section of trim, window sill, or column, may be just the beginning of potentially serious problems. As a fungal infestation, rot can and will spread rapidly unless you take care of the trouble right away. Although replacing damaged wood is often a major hassle -- not to mention the strain it puts on your wallet -- cheer up! A complete replacement is often unnecessary for non-structural-support woodwork. Instead, build up the weakened area with the help of several easy-to-use products. Here’s how.

1. Eliminate the cause. Missing or loose roof tiles, plumbing leaks, poorly fitting doors and windows, inadequate stone pointing, and condensation all admit moisture into your home and allow rot to develop. Signs of dry rot (which, despite its name, actually requires a moisture content of at least 20 percent) include discoloration, splitting, crumbling, or flaking of the wood, and an unpleasant mushroom-like odor. Wet rot occurs in areas with at least 50 percent moisture content and usually shows itself as black fungal growth on wood, combined with a spongy, damp texture. After you fix the origin of the problem, if it is indoors, open as many windows as possible and ventilate the room using fans and dehumidifiers.

2. Remove the rot. Once you’ve identified rot anywhere in your home, the next step is getting rid of all the affected wood -- essential before you begin to repair. Cut out only the rotted section of your wood (a 5-in-1 painter’s tool or a sharp putty knife is ideal for this task). Use a vacuum cleaner to tidy up any sawdust and other dirt.

3. Purchase a wood hardener and a filler – either polyester or epoxy – that are low odor and free of hazardous volatile organic compounds (VOCs). Wear rubber gloves when you work with these substances.

4. Use a small to medium brush to spread the hardener onto the surface, filling in cracks and completely covering the wood which surrounds the area where the rot was found. This will solidify and strengthen it, in order to protect its structural integrity.

5. Next, mix a batch of wood filler. It should be the consistency of peanut butter when ready. Apply generously (any extra can be sanded off later) with a putty knife, shaping it to roughly the shape and size wanted. For large repairs, you may wish to construct a form to help mold the filler. Wood filler dries fast, especially on a warm Southern California summer day, so follow the lead of skilled San Diego handymen  and work as quickly as possible. As the filler hardens, apply a 2nd, and if desired, a 3rd coat. After all coats have completely dried, sand and clean off any dust left behind.

6. Prime the repaired section and then paint it to match the rest of the object. Use anti-fungal paint for the best results in guarding against future problems with dry or wet rot.

Laura Firszt writes for

Updated June 20, 2018.

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