How to Fix Rotted Wood with Epoxy | This Old House (2024)

Automotive body filler (Bondo) available in "Classic" and stranded reinforced formulas for heavy build-up applications works very well at a fraction of the cost of the product that you are demonstrating. I've used it for rotted wood moldings and frames for 40 years, particularly useful for 100 year old Victorian scroll work moldings that are difficult to reproduce today. Applications on my own home that are 20 years old are holding up fine and undetectable today. Bondo is also a two part epoxy that can be drilled, sanded and shaped with common woodworking tools and no special applicator required.

I like how Tom cut a special template from the plastic putty knife to have the correct profile of the wood. Very cool!

Love Tom Silva,I have watched him for over 25 years and he always has something new for me to learn ,thanks Tom !

I save the wood "dust" from sanding and use it when mixing epoxy. It stiffens the mix and makes it easier to sand. It works as well as expensive fillers.

its like being a house dentist

I like the second way he mentioned. Take out just the rotted part and replace that with a small piece of wood. Saves time, effort and money.

Tom, after I learned about this product, I have kept a supply in my garage for the next project that pops up. Your window project in this video was a large undertaking and I have never taken on a project this large before. I have used this on window brick mold and other applications on the exterior of my house. Currently using it on my French door threshold. I have found in the cold weather it can take a lot longer to setup. I always get nervous thinking maybe I did not mix it correctly. Recently ART was sold out of the large double tube, which I love to use with the caulking gun. Due to Covid shortages they were having trouble getting stock for the large double tube. I was encouraged to order the smaller project size, which I do not like as much, I found when I went to reuse the smaller tube after a couple months, there was some hardening at the applicator tip area. I recently saw ART had the larger tubes in stock, so I bought one. It is great stuff.

I still miss this old house and not to forget norm

great tip about making a tool to match the profile I could have used it yesterday Thanks Tommy

Cutting that knife for your perfect custom shape is such simple genius!

It’s interesting to see that after grinding out the rot you can see the very tips of a finger jointed brick molding. When building my house some 30 years ago I installed 27 windows all of which came with brick molding made out of finger jointed scraps. Over the last 10 years I’ve had to repair or replace almost every one of those brick moldings AND all the rot started in the finger joints. Something I wish I had considered when making the purchase.

So wonderful to see an expert at work. Not enough worker like Tom Silva.

Show the whole process, beginning to end! I want to see the repair after it's painted.

This is very cool! I have a couple of rotten window sills on my house and this technique should do the trick.

Tom is so clever. I love watching him work.

Great video! Good explanation of the contractor grade versions of this, but there are super easy homeowner ways to do this too. JB Weld 'Kwikwood' is a putty that you knead the parts together and once mixed you just press it into the void after clearing out the rot. You can easily knead it and shape it for about 20 minutes before hardening. After 1 hour it can be sanded and painted. Nowhere near as messy as this. The end result is surprisingly tough and blends very well with the wood.
Tbh, this rot is so extensive it would have been easier to rout out the remaining wood square-ish and cut a filler piece of wood to fill this large area.

I am working on a rotted window sill much like the one in this video and I like how Tom made the template to match the profile of the molding. Instead of using an epoxy, which can be pricey, I have decided to use some foam insulation and Bondo.

I learned from watching this video that we can tackle this ourselves! Thank you!

Thank you that was very good info. It will come in handy this spring, as I fix a. Few spots i noticed this winter.

This man is a master of his craft.

YOU GUYS ARE AWESOME tom teaches me so much I want to be a carpenter when I get older too

Damn good show. I've been watching for many years. Thank you PBS.

Another use for epoxy. I have two forty year old shovels that are badly weathered and cracked. I smeared epoxy into all the cracks and completely covered the wood. Smooth, shiny and solid.

Been using auto body filler for this for 10 years. I stay at that house today and it showes no signs of failing.

If there is a big cavity that needs to be filled, you can use scrap wood blocks to make the epoxy go further.

I'd like to see how to fix windows made of field built wood frames attached to structural corner posts and go floor to ceiling where the bottom sill details is also baseboard trim detail where there's nothing really on the market to replace such big things and also preserve the look of the original mid century modern 1952 look.
But still I thank you for all the woodworking tips ! Your show helps demystify and builds confidence !

I love RUclips I'm a visual learner this is great!

Thanks for sharing this great strategy

Brilliant. Hope this works for me on one of my crank outs. I doubt it.

Love the video. My house, is 1880 years old,, lol the kitchen windows show this the most. In the spring of 2021 I will attack these areas better armed with the knowledge I gained today 8 Nov.20.... well done Guys.

Thanks!! I now know what to do for a couple of window sills. 👍

In the larger voids use screws so the expoxy binds to the screws as well making a much better bond.

I have used Bondo, which is used for auto body repairs. Works well and cheap. Purchased it at Lowe's

Awesome! Would of liked to seen it finished thought!

Thanks for this invaluable information

helpful information, thank you for sharing !!

Love the trick with the knife

Outstanding. I buy my epoxy by the half gallon and one of several thickening agents.When dry, its solid like plastic and a little flexible. Great video. I have done the same thing around my home, several times. Process confirmed. Fantastic

Thank you for the video very nice job! I appreciate how you show how to do the template with the spatula. I fixed 3 rotten wood beams and 3 window sills. I took away the wood rot first , then apply a product call Rotten wood restorer by Bondo. It really harden the wood in few minutes. Then i used Wood Bond, sanded it and painted it. Looks great!

There is a 4th way! I used some cheap all-purpose filler from Wilco (UK). It's cement based and not the usual plaster one.

I started using a lot of epoxy and polyester resin with and without fiberglass strands, or microbeads or colloidal silica on my house after buying a boat!

Keep in mind one of most hazardous things you can do with epoxy is to start sanding it before it's fully cured. So scrape, cut but don't sand until the next day.
I've made some wooden strip kayaks and so I've used a lot of epoxy. The cheapest easiest way I might deal with this rotted wood work is to get a less expensive brand of epoxy, mix it up (as a liquid) then add filler. A filler I've used many times in a pinch was instant pancake mix. Baking flour (that Gold bond stuff that keeps dry for a year? It's not really food anymore) makes a great filler. Mixed in with the epoxy I've never had any bugs or problem. If you mix your epoxy and then add the filler right away you get longer working time. If you let the epoxy sit mixed for 5 minutes, then add the filler, it goes off a lot quicker.

This is exactly what I needed to know. I have a Catalina Macaw which has chewed up several interior doors and other parts of my house. Is that a special 2-part epoxy made especially for wood?

Slick Trick with the putty knife making template

He is Using Flex-tec HV (see at 2:07). At $200+ per twin Bottle kit of Epoxy, I might as well pay for the wood replacement...

My new project for rotten pation door. Thanks

As soon as I get the epoxy mixed, is when it starts raining.

West System product is the way to go. I usually put in a new piece of wood but keep coating all endgrain with unthickend epoxy many times until the wood will no longer draw it in like a straw. Then I thicken a batch with chopped cotton 406 and paiste it in. Your turning the crappy wood you can get today into plastic basically. Grind and file to sculpt the patch. Prime and paint. It's labor intensive but a lot cheaper than ripping everything out and flashing it all correctly and replacing. With the wide growth rings in the lumber that's available today carefully epoxy sealing endgrain on for example wood brick molding is an extra step worth taking.

Not sure what he used for bonding agent. Years ago I prepared soft rotted window sill areas with liquid thin penetrating epoxy that wicked in through the wood about 1 inch. It made soft wood fibers into hard plastic fibers never to rot and ready for filling. I bought it from *"The Rot Doctor"*

The problem with this lies in the cost of this epoxy kit.
It cost more than replacing the whole window trimming

That was awesome

Flexible epoxy must ne something like an isosianate. Pretty cool

Thank you

Bondo makes an all purpose "fill" for about $11 per tub. Might be a bit more difficult but works beautifully and can be painted/sanded.

It's actually much easier to just get a can of auto body Bondo. Works fantastic! And easily sanded and then painted.

Epoxy, great idea! What kind of epoxy and bonding agent [brands?] ? There are many.
I have a large project and need bout a gallon.

Great video

I've used the Bondo on exterior repairs and it does crack in some instances. As far as Minwax it's it's basically Bondo. I do like using the wood hardener Minwax makes. I would like to use the epoxy stuff that they use then then make my decision on what is best

Smart using that rubber mat on the front porch.

I've tried this myself using JB Weld Wood Epoxy. It works but it's pretty difficult to make it look as good as new. If you only have a tiny amount of rot this might be the easiest and cheapest method, but next time I run into this situation I will probably just replace the wood.

We should be done with this small repair in two to three days.... 🤣

Wonderful display You have inspired me to work on my channel, thanks. 🐼

Great job

One thought on the Bondo use, i thought it absorbed water, that is why we need to use tiger hair when filing in a rust hole and not go straight to bondo. Bondo is so easy to use and sands so nice, i can see how convenient it would be in this application.

Tommy Silva is the man!

Thanks

I like what I see, but I need to get it in writing. I had a head injury in 1986 on a motorcyle and it is hard for me to remember. Thank you.

Where can I find the epoxy? his looks great!

I use Durham's "Rock-Hard" Water Putty. It only lasts around 10 years - longer if you prep the surfaces properly and paint it well, but it costs under $10.

I just bought this stuff and it is perfect for the job I needed to do in our corner window. For that window the number of parts that would have to be removed would be time consuming. With this you dig out all the rotten wood, sand as much as possible, pretreat with the bonding agent and will the void. It dries very fast. Sand and paint. In the future when all of the siding is replaced that would be the time to replace the wood window surrounds, not now.

your channel is awosome

Hi, thanks for this video! I dug out some rot from the bottom of a couple of exterior door frames. The resulting spaces are each about the size of a baseball or maybe a little bigger. Would it work to fill the holes with "great stuff big gap filler", trim it to be almost flush with the door frame, cover with a little regular wood filler, and paint? Hope that's not a dumb question. I already have all these materials, so that would be convenient, rather than buying epoxy/etc. Thanks!

Before I purchased my house the previous owner had a contractor repair a sill using car bondo, this allowed the water into and around the entire window. The entire sill and surrounding wood rotted out and now I have to replace the window, window sill, frame, and flashing. Real wood and a real contractor is my next choice!

As a handy man I use Durham's Rock Hard water putty. Home Dumpo has it and is a crap-ton cheaper too. In the paint isle.

Looks like a great idea, as long as someone else pays for it.

What bonding agent do you apply before you apply the epoxy ?

Great tip. Thanks guys.

Make sure to always paint your epoxy to prevent UV damage

I use Bondo, a gallon is like $16.00. Works Great for wood and i still have a lot left for Auto. Repairs.

We use that on wooden boats that used to call it get right but basically it's just a poxy injected into the wood and it makes it as good as new even stronger I believe

I wonder if epoxy gives any structural strength? I have a table with rotten legs. I wonder if this is strong enough to support the table (around 15kg weight) or I'd better replace the legs.

I already tried to use some regular wall putty, but it's too liquid to shape.
Can I put epoxy on top of another wall putty ?
Or I have to remove the wall putty first ?

People rarely show the staining or painting of these fillers, especially the homemade ones.

bondo cheaper and sets up faster. also you need to add something to the large holes for the epoxy to grip or it will eventually fall back out. nails or screws into the good wood will work great.

Question: If the rotted part is touching something prone to moisture, such as a concrete slab, will repairing the wood with epoxy prevent rotting in the future? Or will the moisture transverse up into the wood above it?

I love your video. But are there simple materials we can use now .?

Smith's is a good local (bay area) brand of paste two-part filler; they also make a two-part hardener. Pricey of course but for me, worth it. However, I am very skeptical Tom could match the shapes in a single application: better to do a first fill, dry, then a topcoat. Some of my repairs on my old house are 20 years old and solid.

What about killing the fungus? Isn't that a must before covering over the affected area?

Bondo works well to

This looks fine, except for the skim coat applied on the face of the sill. Epoxy does not allow liquid water or water vapor to pass through itself. When you apply a skim coat over the face of the sill, moisture can be trapped inside the wood, leading to accelerated rot and the skim coat separating from the sill. 5 yrs seems to be the lifespan of this kind of repair in the humid philadelphia area.

You can use Bondo and it works really well and a lot cheaper than epoxy and it's paintable as well

Thanks Tom good fix...

What about the right corner of the Upper sash. Will epoxy fall down?

is the bonding agent necessary since it's not listed on the shopping list? seems like there are a lot of types of bonding agents.

Need this on a house that I own.. I'm not talented like this... Don't have a lot of time either for a project like this..

System 3 Rot fix kit is a much easier way to go and a lot less expensive.

I used car body dent filler!

I watched this while waiting for the dentist ......

The only problem using these products is after time the wood expands and contracts around the filler ( which does not) and cracks around the filler show up. I think an exterior nylon based powder filler lasts much longer.

I have to admit from the way I have seen wood rot travel.I would pull the boards if possible and replace them.That way you can see if it traveled on any of the other contact pieces.Wood rot is no joke.