What is a good wood epoxy for strengthening a floor joist?

Empty Nest, Soon wrote:
Drilling holes will be no benefit. You will probably be removing good wood and the thinned epoxy will still only penetrate by a tiny fraction of an inch. Kill the rot with TimBor or anti-freeze. Explore with an awl to ensure that no rot lies slightly below the surface. If all seems good, the deeply buried wood is probably fine. Drill a few exploratory holes if you must to satisfy yourself that the remaining wood is good. Then fill the holes so they don’t collect water. There’s no point in making Swiss cheese out of the joist.

I'm glad that you said that, because I've been debating how far I wanted to go with trying to strengthen the existing joist. I see the benefit in drilling holes to put in CPES, but it does seem like it would be a trade off since, as you said, I'd be removing good wood in the process.

I think I'll get as much antifreeze on it as I can. Then I'll replace the worst of the rot with good wood, and put CPES in the holes that I drill for the sister joist. That will at least give the screws something solid to bite into if there is any rot in the middle.

I feel like I have a battle plan! Going to tackle it tonight. Will let you guys know how it goes.

To their credit, Smith & Co., who makes CPES, does not market it as a miracle dope to make sound wood out of rotten wood, although lots of others make that claim. It is a sealer, and does a fair job of that on new wood. It makes a great surface for paints to stick to. But if excess moisture or rot is already in the wood, all CPES will do is better seal it in the wood.

Drilling holes will be no benefit. You will probably be removing good wood and the thinned epoxy will still only penetrate by a tiny fraction of an inch. Kill the rot with TimBor or anti-freeze. Explore with an awl to ensure that no rot lies slightly below the surface. If all seems good, the deeply buried wood is probably fine. Drill a few exploratory holes if you must to satisfy yourself that the remaining wood is good. Then fill the holes so they don’t collect water. There’s no point in making Swiss cheese out of the joist.

After you put in the sister(s), the original joist is basically without a job anyway. If you can sister all the rotten joists, that is the way to go.

Wayne

owenssailor wrote:
I have a 52 year old 38 foot sailboat. Over the years have had to do various repairs.

The best option is to cut out the rotted area, make a new piece to fit and then epoxy and screw it in place.

The next option is to use West System epoxy with their high density filler and fill in the area where the rotted wood was.

I tried Git Rot years ago. It did help but when I later took that area apart there was hard wood at the holes where the Git Rot was injected but still soft a few millimeters away.

If you have questions plse let me know

I won't dispute your findings, but I wonder how far apart your holes were? Was it solid teak, or ply? I honeycombed the area covered by the base of the mirror with 1/4" diameter holes every inch or so and really saturated the 3/4" plywood beneath the fiberglass skin. I'm not about to tear it apart to see the extent of the saturation, but not only did the mirror's four large screws bite and hold firmly, the previous spongy feel and sound of the area was gone, as well. When pulling hard on the mirror mount in any direction, the wall surface no longer moves at all. In my case, where I did not want to tear apart the sandwich wall to affect a repair that would have been a cosmetic mess, the thin epoxy served me perfectly and I am still delighted with the results.

To each his own, and different solutions for different situations. In the OP's case where the damage is totally exposed and accessible, I will concede to your advice.

Empty Nest, Soon wrote:

owenssailor wrote:
I have a 52 year old 38 foot sailboat. Over the years have had to do various repairs.

The best option is to cut out the rotted area, make a new piece to fit and then epoxy and screw it in place.

The next option is to use West System epoxy with their high density filler and fill in the area where the rotted wood was.

I tried Git Rot years ago. It did help but when I later took that area apart there was hard wood at the holes where the Git Rot was injected but still soft a few millimeters away.

If you have questions plse let me know

What he said!

There are several places that promote expensive thinned epoxy (CPES, or similar) as a miracle snake-oil to make sound wood out of rotten wood. Baloney! There's no way to get it to penetrate far enough to do much good. If you want to give it a try, it is cheaper to thin epoxy 50/50 with xylene, but I say you're wasting your time.

Get the rot out by cutting if possible. Kill remaining rot spores with one of the borates made for the purpose (TimBor, etc) OR by saturating with old-fashioned ethylene glycol anti-freeze, (e.g., Prestone) which penetrates wood exceptionally well and is toxic to rot.

Grave in a replacement piece or sister with good wood beside the bad place.

Wayne

Apologies in advance for the long post...

Thanks as always for the assistance! Everyone on this forum is great. Figured I would just respond to these two posts since they captured everything people said.

There are three parts to the repair that I'm doing, and this is the order that I'm doing them in:

1. Repairing the weakened joist (which is what this thread is about).

2. Repairing a section of the flooring above the joist that was rotted and that I can't cut out. I put a picture of that below. I can't cut that section out because it would require going under the slide. That's just not an option for me because of A) lack of skill, and B) a place to do it. We travel full time and won't be at home base until December. I'm in an RV park right now.

3. Putting in sister joists to replace the floor that I cut out and offer support to the weakened joist.

The way I see it, I have a few options here. Please correct me if there are better ways to do this (again, without cutting under the slide.

Solution 1:

* Dig (or cut) out the rot
* Put a product like Timbor on the wood to kill any rot
* I do have CPES already so I am going to go ahead and put that in the wood that isn't visibly rotted, but might be rotting internally. I plan to just drill 1/2 inch holes at a 45 degree angle into the joist and inject the CPES. I figure it can't do any harm!
* Once all this is done I'll either patch the wood, like you guys suggested, or fill it with an epoxy. I need to go to Home Depot and see how much a rotary tool is that can make the cut. If it's more than about $100 I'll probably just use epoxy. My wife and I are on a debt free plan so we're trying to save money :).

Solution 2:
* For the section of floor that is rotted above the joist, I plan to just put some Timbor on it, patch it with epoxy, and then also put some CPES around it for good measure. That wood doesn't need to be super firm because nobody ever puts direct weight on it. There is another joist right beside the one that is rotted, underneath the slide. There's a gap of only about 3 inches between the two. So that section of floor just needs to be firm enough to not sink when someone puts a little pressure on it.

Solution 3:
* Slap in some sister joists and make a couple of squares, lay new flooring down.

Does all that seem about right?

Also, here's a follow up question: Do you guys have any tips for making the sister joists not squeak? I'm definitely not a carpenter! I've read that putting epoxy between the joists and then screwing them in is the way to do it, but I'd like to get it right the first time!

Thanks

Edit: Forgot to link the pic to the section of flooring that I'm going to patch (step 2). - https://www.dropbox.com/s/2eigoi3exwkxtws/2015-10-05%2011.18.14.jpg?dl=0

West systems epoxy have fallen behind the times. Lots of blush, yellowing, secondary bonding issues, hard ratio to mix accurately, but granted not much of an issue in the OP's requirements

My Favorite epoxy is System3, the SB112 and Clearcoat resins for laminating fiberglass cloth onto wood. Have not tried their new silvertip resin.

They have various rot fix products too.
http://www.systemthree.com/store/pc/Rot-Repair-c33.htm

Their clear coat resin is pretty thin stuff, and cures very slow, Good for when a bunch of epoxy cures in a thick mass.

Epoxy creates its own heat so if a large mass is to cure, it can generate too much heat and expand, then shrink afterwards and compromise the bond.

owenssailor wrote:
I have a 52 year old 38 foot sailboat. Over the years have had to do various repairs.

The best option is to cut out the rotted area, make a new piece to fit and then epoxy and screw it in place.

The next option is to use West System epoxy with their high density filler and fill in the area where the rotted wood was.

I tried Git Rot years ago. It did help but when I later took that area apart there was hard wood at the holes where the Git Rot was injected but still soft a few millimeters away.

If you have questions plse let me know

What he said!

There are several places that promote expensive thinned epoxy (CPES, or similar) as a miracle snake-oil to make sound wood out of rotten wood. Baloney! There's no way to get it to penetrate far enough to do much good. If you want to give it a try, it is cheaper to thin epoxy 50/50 with xylene, but I say you're wasting your time.

Get the rot out by cutting if possible. Kill remaining rot spores with one of the borates made for the purpose (TimBor, etc) OR by saturating with old-fashioned ethylene glycol anti-freeze, (e.g., Prestone) which penetrates wood exceptionally well and is toxic to rot.

Grave in a replacement piece or sister with good wood beside the bad place.

Wayne

I have a 52 year old 38 foot sailboat. Over the years have had to do various repairs.

The best option is to cut out the rotted area, make a new piece to fit and then epoxy and screw it in place.

The next option is to use West System epoxy with their high density filler and fill in the area where the rotted wood was.

I tried Git Rot years ago. It did help but when I later took that area apart there was hard wood at the holes where the Git Rot was injected but still soft a few millimeters away.

If you have questions plse let me know

No need to epoxy the rotted area; I doubt it would add any strength. You're on the right track by sistering it.

Abatron makes good products, maybe less expansive than the West System stuff. I have used the Liquiid Wood and WoodEpox both. Good stuff.

From my days with boats (even more of a money pit than RVs!) I learned of a product called Boatlife GIT-Rot. I recently used it on my motorhome to restore the rotted plywood panel sandwiched in the side-wall behind the right hand-side mirror. I had to replace a damaged mirror that some dolt, who shall remain nameless, had managed to knock off going through a toll booth lane! :o The underlying plywood had rotted to the point that it would no longer hold the mounting screws for the new mirror. I thought that an expensive and difficult wall surgery was going to be necessary until I remembered the GIT-Rot. A half-hour's work and an overnight cure left the wall stronger than ever.

It's a thin, two-part liquid epoxy that you squirt into drilled holes in the rotted wood without removing the rotted portions. By capillary action it permeates all the spongy, rotted wood fibers and cures overnight, leaving a wood/epoxy amalgam that stronger than the original, undamaged wood. You should dry the rotted area as much as you can with a hair dryer or heating gun set on low, but the stuff will even work on slightly damp wood, as it did with mine.

Here's the YouTube video: GIT-Rot demo

I got mine at Amazon, here.

Just make sure you follow the directions carefully when it comes to temperature, mixing, and curing time. Also, if you are drilling on the vertical side of your beam, slant the drilled holes downward to allow the epoxy to flow into the wood and not spill down the surface.

Good luck. I hope it works as well for you as it did for me.