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How to Use Epoxy on Wood for Repairs

Epoxy is the perfect material to make permanent repairs of rotting window sills, door jambs and exterior molding that are difficult to remove and expensive to replace. Epoxy is easy to handle too. 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.

By the DIY experts of The Family Handyman Magazine

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    Small repairs are simple; larger repairs are more difficult, especially when you have to shape the epoxy to match curves.

How to Use Epoxy on Wood for Repairs

Epoxy is the perfect material to make permanent repairs of rotting window sills, door jambs and exterior molding that are difficult to remove and expensive to replace. Epoxy is easy to handle too. 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.

By the DIY experts of The Family Handyman Magazine

Overview: Epoxy basics and where to get it

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 Play-Doh. 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.

You will find many brands of epoxy. The exact mixing and application procedures vary a bit depending upon the manufacturer. Follow the manufacturer's instructions carefully. The brand we're using has a two-step system, which 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.

Sometimes epoxy is available at large home centers. Otherwise, you can find it on the Internet. Or see “Marine Equipment and Supplies” in the Yellow Pages to locate other sources of epoxy for wood repair.

Step 1: Clean out and prep the rotted area

The 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.

After 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 (Photo 2). Old paint may contain lead. If so, use lead-safe paint removal techniques. Next drill a series of 1/4-in. holes spaced about 1 in. apart around the repair (Photo 3). 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.

Step 2: Apply and shape the epoxy

You don't have to wait for the consolidant to harden completely before filling with the epoxy wood filler (Photos 4 — 7). Mix the epoxy filler (Photo 4) and use a stiff putty knife to work the first layer into the wood (Photo 5).

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.

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.

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.

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.

Caution!

When using epoxy solvents, work outdoors in a well-ventilated area, or wear an OSHA-approved organic Vapor respirator with fresh cartridges.

Step 3: Fine tune the shape, smooth and finish

When 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.

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.

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.

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Required Tools for this Project

Have the necessary tools for this DIY project lined up before you start—you’ll save time and frustration.

    • Hammer
    • Drill/driver, cordless
    • Drill bit set
    • File
    • Putty knife
    • Rasp
    • Wood chisel

Gloves, chemical resistant

Required Materials for this Project

Avoid last-minute shopping trips by having all your materials ready ahead of time. Here's a list.

    • Epoxy
    • Wood consolidant
    • Sandpaper, 80 and 120 grits
    • Small (8 oz.) squeeze bottle

Comments from DIY Community Members

Share what's on your mind and see what other DIYers are thinking about.

1 - 9 of 9 comments
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May 02, 3:19 AM [GMT -5]

Conventional epoxy repair materials fracture under the stress of constant movement. Most epoxy repair compounds lack the flexural strength required.

May 02, 3:17 AM [GMT -5]

Epoxy Adhesive are triple distilled to provide the highest industrial strength and resistance properties with consistent performance for every assembly applications.

http://www.parsonadhesives.com/partite-parbond/epoxy-adhesives.htm

hoz

March 07, 1:57 PM [GMT -5]

I've used epoxy to repair rotted wood for years. Don't purchase the formulated brands. It's less expensive and you have more control using regular two part epoxy resin. It is sold to build wooden boats and canoes, among other things. I purchase from http://www.uscomposites.com/, but there are many different suppliers.

Use the epoxy mixed "neat" with a little added denatured alcohol as the "consolident". Just flood the mixture into the rotted area after clearing the loose wood away. A similar formulation has been sold for years as "GIT-ROT."

Once that solidifies mix epoxy and add filler to make your putty. I like a mixture of fine sawdust and colodial silica (cabosil or fumed silica). But just about any dry powder will work, from unscented talc to regular wheat flour!

I always keep a quart of epoxy resin around for repairs.

March 09, 4:02 AM [GMT -5]

I have heard of a few of the high power guys talk about this brand, but never seen it myself. From the intel I viewed on West System's website, it looks a little more complicated than a simple 1 to 1 mix.
http://www.parsonadhesives.com/partite-parbond/epoxy-adhesives.htm

January 03, 2:59 PM [GMT -5]

I have used automotive epoxy in the past and it has worked like a charm. Drying time is a bit longer, but the end result is harder and permanent.

June 07, 9:09 PM [GMT -5]

Epoxy worked fine to fill a large crack in a window frame but wouldn't hold well on a badly damaged window sash. What would you suggest.
Elvie

October 26, 9:14 AM [GMT -5]

Epoxy is the perfect material to make permanent repairs of rotting window sills, door jambs and exterior molding that are difficult to remove and expensive to replace. <

June 03, 5:34 PM [GMT -5]

can the epoxy method be used on rotted window sills?

Thanks

May 23, 12:34 PM [GMT -5]

Very good article. After reading it and realizing how easy it is I am getting ready to hit the hardware store and complete my own project. Thanks, Giuseppe Lombardo

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