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Rotted Sills, Rotten Wood and Epoxy Rot Repair Page

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Paul Oman, MS, MBA - Progressive Epoxy Polymers, Inc.

Member: NACE (National Assoc. of Corrosion Engineers), SSPC (Soc. of Protective Coatings)

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There are lots of rot repair pages and epoxy products available. The attempt on this page is to put it all in perspective, outline the general basics and theories, and than (of course), mention the products we sell.

THE SAD TRUTH

Despite claims by many companies, epoxy sealers, penetrating epoxies, etc. will not fix, damp/wet rotted wood. The epoxy may or may not bond to the wet wood (some epoxies bond to wet surfaces) but it will not 'drive the dampness out of the wood' and replace it with hard epoxy. At best the epoxy will stick the the wet rot surface, still leaving the 'water' seemingly 'attached' to the wood.

You will note that penetrating epoxy claims are always done with dry sawdust type rot, the type of surface where any liquid will soak into the material. The material in the epoxy that helps it soak into the fibers is generally a traditional solvent. Some products are actually upwards of 70% solvent and only 30% epoxy (which costs more than solvent). I believe 70% epoxy and 30% solvent is a better ratio.

I have tried several times to epoxy 'fix' spongy, soft rotten wood spots on my outdoor porch deck. I've tried all the tricks, and at best I get a hard crust over the area. Still not satisfied, I've always ended up ripping out the old planking and replacing it with new. And I've also found that the rot on the bottom side of the blank was much more extensive than the patch of soft rot on the top side of the plank and that that the 'penetrating' epoxy never got to more than about 5% of the problem.

Window sills, trim work etc. are a different story. They are small areas and no one is walking on them, so it doesn't really matter too much of the fix is not 100%. The goal often is not so much to completely remove the rot as it is to stabilize the surface so that it will coat a coat of paint. Also porch deck planks are easy to remove and easy to drop a new one in its place. Window sills and outdoor trim are a different matter. Replacing or matching them is often more time, money, or skill than most of us have, so that best we can usually do is just a 'decent' patch.

So, the steps below are the results of personal experience and feedback from customers. There are certainly no right or wrong ways but the method explained below, seems to a good one.

OPTIONAL PRE-TREATMENTS

Optional (at this point) - find the rot and remove as much of it as you can.

Option 1) - some people treat the area with glycol (anti-freeze) or boric/acid-salts to kill the fungus spores. (NOTE: This is optional - the epoxy will kill the fungus spores to, but will not 'soak' in as well as the other 'fixes - including 'anti-freeze' see below. There is some concern about bonding to anti-freeze coated surfaces.

In personal tests, I found that anti-freeze penetrated the wood better than anything I have seen (it is attracted to moisture unlike other 'chemicals'). - try it yourself, put a piece of new yellow wood into some anti-freeze and watch the 'stain' migrate through the wood over the next few days. I also found that solvent thinned epoxies stick OK to anti-freeze coated wood and unthinned epoxies will stick decently enough too.

The method is to keep soaking the area with anti-freeze until it will accept no more and then let it 'dry' for as long as possible. This method does have a track record for stopping the rot.

For a third party article on anti-freeze (glycol) use with rotted wood - CLICK HERE

Option 2) - treat the area with isopropyl alcohol. The alcohol is a solvent that will 'mix' with the water and evaporates much quicker than water. Thus the evaporating alcohol will carry with it some of the dampness/wetness in the wood. I suppose the alcohol might also kill some of the rot fungus.

Option 3) - cannot say I have tried it, but I suppose heat lamps etc. would help drive out the moisture and water in the rot area. The drier would would add in epoxy penetration. Also, if the wood were reheated just prior to applying the epoxy, the cooling down wood will 'draw in' the epoxy (as the air contracts and cools) deeper into the wood than if the wood were at room temperature. This 'apply to a cooling down surface' is not theory but a well established and proven technique in a number of epoxy application situations.

REPAIRING ROT

STEP 1

find the rot and remove as much of it as you can (if you haven't already). Let the wood dry as much as possible.

Seal and reinforce the wood with a 'solvent thinned' thin epoxy. Our ESP 155 epoxy is solvent thinned already. Our Low V epoxy is solvent free - you optionally add 0 - 100% solvent to it. Keep repeating this step until no more epoxy will soak into the wood.

STEP 3

If the chipped out bad area is large, some people recommend carving a wooden plug to fill up most of the space - thus saving epoxy and/or epoxy putty and incorporating more 'real wood' into the repair.

STEP 4

At this point you might fill the rot cavity with the chunk of wood and epoxy putty into place. Whether you use the wood plug or not, time to NEARLY FULL the cavity with epoxy putty. Use our Wet Dry 700 epoxy paste/putty which is thickened and reinforced with Kevlar (tm) and will bond to damp surfaces (you can even apply it underwater!). You can also use our non solvent thinned Low V epoxy mentioned in Step 2 and our EZ Thick thickener to make an epoxy paste (approx. 2 parts thickener to 1 part epoxy).

Using an exterior putty (cheaper and easier to sand/smooth - buy from local hardware store) fill the remaining hole. Let harden and sand smooth. It is much easier to sand and shape the non epoxy putty.

STEP 6

Using the same epoxy you used in step 2, coat the putty patch and the surrounding wood. This will 'seal' in the putty patch (locking it away from rain, ice and snow) and prime the patch and the window sill (or whatever) for painting.

You can add pigment to the epoxy, which will make it easier (few coats) to topcoat.

STEP 7

Paint the area with a good quality paint (100% acrylic latex or enamel.

YOU ARE NOW DONE!

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Products offered by Progressive Epoxy Polymers, Inc.

LOW V™ (thin, solvent free epoxy - add solvent to this to make a penetrating or priming epoxy. Add thickeners to form a paste) - Click Here

ESP 155™ (our own clear primer epoxy with approx. 25% solvent - add more solvent for an easy penetrating epoxy) - Click Here

WET DRY 700™ (epoxy paste - bonds to wet surfaces) - Click Here

EZ THICK - (thickening powder for epoxies) - Click Here

EPOXY PIGMENTS - Click Here

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Knowledge is Power - We like informed consumers!

Learn the basics of epoxy at our educational EPOXY 101 page - Click Here.

Finally, email us back with your questions or comments before you buy - EMAIL HERE

OTHER RELATED LINKS ON ROT, EPOXY PRIMERS, ETC.

Penetrating epoxies - www.epoxyproducts.com/penetrating4u.html

Treating rot (this page!) - www.epoxyproducts.com/rot.html

Competitor's penetrating epoxy solvent list - www.epoxyproducts.com/solvents.html

More on primers - www.epoxyproducts.com/primer.html

Sealing wood (tests) - www.epoxyproducts.com/woodseal.html

link to commercial site

Index of epoxy information

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