From About this Project
Damaged wood windowsills, door jambs and moldings can be repaired with two-part epoxy. With the right tools and techniques, you can achieve a long-lasting, good-looking patch.
You can’t top epoxy for permanent repairs to rotted wood. You mix it like cookie dough, mold it like modeling clay and, when it hardens, you carve and sand it just like wood. It sticks like crazy and is formulated to flex and move with the wood, so it won’t crack and fall out like some wood fillers. It’s too expensive to use for boards or moldings that are easily and cheaply replaced, but epoxy is the perfect fix for windowsills and door jambs that are difficult to remove, and for moldings that would be expensive to duplicate.
In this article, we’ll show you how to mix, apply and shape epoxy wood filler to create a long-lasting repair on damaged or rotted wood. We’re using a system of both liquid and putty-like epoxy made specifically for wood repair. The procedure we’re demonstrating is for cosmetic repairs. If a structural (weight-bearing) member has been weakened by rot, you have to use other methods or in some cases special types of epoxy.
Once you learn a few tricks for mixing and applying the epoxy, you’ll find it’s as easy to use as PlayDoh. Most repairs will take only a few hours, using tools you probably already own. You’ll need a hammer and chisel, a drill, and wood rasps and files, depending on your repair. Other materials and supplies are listed in the story.
Buying EpoxyThe wood repair epoxy we’re using is manufactured by Abatron. Other brands are available, but mixing and application procedures vary. Follow the manufacturer’s instructions carefully. The Abatron system consists of two types of epoxy, a syrupy liquid consolidant and a putty-like wood paste filler. The liquid consolidant soaks into the wood fibers and hardens to form a solid base for the wood filler. As with any other epoxy, both the consolidant and wood filler consist of two parts, the resin (part A) and the hardener (part B). Mixing the two parts according to the manufacturer’s instructions starts a chemical reaction that causes the epoxy to harden.
Abatron epoxy is available by mail order and at some large home centers. You can order Abatron products by phone (800-445-1754) or from the company’s Web site (www.abatron.com). A kit containing two pints of consolidant, two pints of wood filler and one pint of solvent costs about $64. This kit makes enough epoxy paste to fill an 11 x 11-in. repair 1/2 in. deep. Search the Internet or see “Marine Equipment and Supplies” in the Yellow Pages to locate other sources of epoxy for wood repair.
If You’re Not Careful, Epoxy Filler Can Make the Problem WorseThe first step in any repair is to find and stop the cause of the rot. Our column base had two problems. First, the column base was sitting directly on concrete where it could absorb moisture. We replaced the rotted base with a new one of rot-resistant redwood and placed a layer of galvanized sheet metal between the base and concrete to keep it from absorbing moisture.
The second problem we had was that the layer of paint meant to protect the wood was chipped and cracked, allowing water to soak in and rot the wood. Once it’s been repaired, this type of decay is easy to prevent by maintaining the paint job. Other causes of rotting wood, like leaking gutters or missing or damaged metal flashing materials, may be more complicated.
If you’re not sure what’s causing the rot or how to repair it, call a building contractor or housing inspector for help. Even after you’ve corrected the problem, make sure you allow the wood plenty of time to dry throughout. This may take a week or longer. Otherwise, trapped moisture may cause additional rot or prevent the epoxy from bonding properly.
Epoxy Won’t Bond Well Unless the Wood Is Thoroughly DryAfter you’ve located and corrected the cause of the rotted wood, start the repair by stripping off the old paint and gouging out all the decayed wood.
Next drill a series of 1/4-in. holes spaced about 1 in. apart around the repair. Drill the holes as deep as possible without going all the way through the wood. The holes allow moisture to escape and later act as reservoirs for the consolidant as it soaks into the wood. If you accidentally drill all the way through the wood, plug the bottom of the hole with oil clay or painter’s putty to prevent the consolidant from running out.
Next, construct a loose-fitting plastic tent over the repair to protect it from rain and let it dry at least a week before proceeding. Uncover the repair on dry, sunny days to speed up the drying process.
Preparation and Cleanliness Are Essential When You’re Working With EpoxyOnce the wood is thoroughly dry, vacuum or blow the dust out of the repair area. Then start the epoxy repair by mixing and applying the consolidant.
Mixing the liquid epoxy consolidant in a squirt bottle makes it easier to apply, and if it tips over, you’ll only have a few drips to clean up. Graduated bottles like this are available for about $2 at beauty supply and woodworking supply stores.
Keep your work area clean and organized, and keep the area surrounding the repair covered with paper or dropcloths. Use disposable brushes, plastic putty knives and scraps of wood to minimize tool cleanup. Wear chemical-resistant rubber gloves to protect your skin. You’ll need a powerful solvent like naphtha or a special solvent available from the manufacturer to clean up epoxy before it hardens. Minimize solvent use by cleaning up drips and spills right away with paper towels.
Tips and Buyer's Guide
Epoxy’s behavior is predictable, if not always desirable. If you inadvertently put cap A on container B, it will glue itself on. Label all the lids and mixing sticks to avoid confusing them and starting an unwanted reaction. Also, always use clean containers and mixing boards. Contaminating newly mixed epoxy with partially hardened epoxy can accelerate the reaction, leaving you less time to work.
Caution: When using epoxy solvents, work outdoors in a well-ventilated area, or wear an OSHA-approved organic vapor respirator with fresh cartridges.
You don’t have to wait for the consolidant to harden completely before filling with the epoxy wood filler. Mix the epoxy filler and use a stiff putty knife to work the first layer into the wood. At 70 degrees F, you’ll have about 30 minutes before the epoxy starts to harden. The epoxy is formulated to allow enough working time under normal conditions, but temperature is the key factor. Heat accelerates the reaction; cold slows it down. Use this to your advantage. Work in the shade and keep the epoxy materials cool (about 70 degrees F) when you’re mixing and applying the epoxy. Then if you want to speed up the hardening process, use a hair dryer or a spotlight to warm up the epoxy repair.
Tip:
Don’t waste epoxy when you’re making large or deep repairs. Cut or carve blocks of wood to fill most of the cavity. Then use epoxy paste to glue the block in before covering it with additional paste filler. Use the same kind of wood for the repair and line up the grain in the same direction.
You Don’t Need Fancy Tools to Shape the Epoxy
Shape the epoxy with your fingers and by patting it with a scrap of wood. Don’t try to get the shape perfect, and make sure to leave enough material to match the surrounding profiles. On warm days, the epoxy will be firm enough to start shaping in about three to four hours. In cool weather, allow the patch to harden overnight. If you can’t dent the epoxy with your fingernail, it’s hard enough to start filing. Once it hardens, epoxy is easy to shape and sand with standard woodworking tools. Start by roughing out the basic contour with a Surform plane or coarse rasp. Follow the shape of the surrounding wood. When you’ve ground off the major humps and the shape is beginning to emerge, start working on the details. Depending on the profile you’re re-creating, you may need flat, round or half-round wood files or rasps, or wrap 80-grit sandpaper around a dowel or fold it around a stick and use this to grind out the shape. Use the profile of the surrounding wood to guide your tools as you gradually file away the epoxy. Fine-tune the shape and get rid of the sanding marks by sanding with 80-grit and then 120-grit sandpaper.
Tip:
When you do the final sanding, make sure to rough up the surface of any hardened consolidant that may be coating the surrounding wood. Otherwise, the paint may not stick.
Don’t worry if you file away too much epoxy or didn’t use enough to begin with. Many repairs require a second application. Dust off the repair and mix and add more filler. To make a thinner filling material that’s easier to apply, first mix a small amount of consolidant. Then mix a small batch of filler and add some of the consolidant to the filler to reach the desired consistency. If you’re in a hurry to sand again after you touch up the repair, heat the new filler with a hair dryer to speed the hardening process.
Protected with a good paint job, your epoxy repair will probably outlast the surrounding wood.
Buyer’s GuideThe following companies manufacture epoxy products for wood repair. You can buy directly from the manufacturer or through special suppliers.
Abatron Inc.: (800) 445-1754. www.abatron.com
Housecraft Associates: (973) 579-1112. www.conservepoxy.com