Does any one have any experience with repairing structural wood with 2-part epoxies? I'm not referring to simply patching surface areas with pastes or putties, but more along of the lines of injecting liquid two-part epoxy into structural wood in situ in order to fill voids and cavities from insect damage or dry rot and to force moisture out.
I have a lot of experience myself using epoxy in fiberglass boat repair, with much success. But the problem as I see it regarding wood is that a fiberglass hull is supposed to be totally stiff and stable. Whereas wood is going to expand and shrink. The argument against is that wood movement is going to work against those parts of the same wood that have been saturated with epoxy and immobilized, and that this might in time result in more damage and undermine the structure. The argument for is that if the wood has been severely compromised anyway, why not inject it and make it into something stronger than it had been? Especially if the wood has historic value and the only alternative would be to replace it.
Any opinions on different brands? E.g., WEST Marine vs. Abatron?
I would say it depends on the size of the repair.
Basing this answer on my hobby of turning wood bowls. I use some spalted wood. This is rotten wood. Turners stablize punky areas of a blank so it can be turned. We use Super Glue, 2 part Epoxy, and other wood stabilizing products.
Typically these areas are relatively small. A Turner will not get too worried about the wood moving and the stablized part not moving.
So now we apply this to a piece of wood in a historic house. How large - and in a house, what is the orientation and purpose of the wood?
Size and Orientation: Wood moves across the face, not from end to end. Think of your board as a bunch of straws. A 2x4 (brand new or 100+ years old) will have the open ends of the straws at the ends of the 2x4. So moisture movement will not occur in the length of the board. It will occur across the 2 inches or 4 inches of the 100 year old board.
You have to look at that part of the wood that will be stabilized and think it through. Which way will the wood move? The stabilized joint may or may not cause a problem.
My, very limited, experience with historical buildings, I've done an audit for a period home owned by a City Historical Preservation Staff member; was that if a piece was replaced it had to look like the original. Windows were the discussion item. It was OK to replace the rotted sill of a window, because that was a restoration.
I would appreciate more input on this one.
Both will work fine, though I generally prefer WEST system - I haven't seen any issues created with them as far as expansion & contraction - Bondo on the other hand can pop out. WEST systems has some really good info on their site for binders, fillers, etc... which I highly recommend checking out.
For deep injections - I would lean more towards Abatron, though I try to get all the bad wood out where possible
For window profiles and others - I trim down one of those cheap plastic putty knives & press the material in as much as possible before pulling across it once
West System is the best. The cost is higher than some, but not as bad as a few others. You can buy various open times. I know guys that like a 30 minute open and others that like 5 minutes.
Wood never drops below about 6% moisture. It will move up and down from there, depending on the relative humidity and temperature.
It's a relevant question to the extent that it could be an aspect of the repair and preservation of historic sheathing, roof decking, siding, historic windows/window framing, etc., as part of (or perhaps as a prerequisite to) the energy retrofitting of an historic structure. To some extent, it also presents something of a requirement for the indoor environment in terms of control of moisture, temperature, and ventilation. I would agree that it's decidedly not relevant to more general aspects of energy auditing & retrofitting, etc. But for this particular group, I think it's reasonable and not necessarily off-topic. (Same goes for an earlier question about how to deal with dry-laid stone as part of sealing/insulating an historic foundation, just as an example). Anyway, thanks for joining the Historic Home group, Kevin, and thanks for commenting.
David, thanks very much for this very detailed and highly informative reply. I have worked with WEST system a lot in fiberglass boat repair, and am familiar with their hardening and filler options, and yes, like you, I've also ended up having to toss unused resin when the hardener runs our first! A bit frustrating. I am in the process of trying Abatron, but haven't used it seriously on any projects yet. The Smith & Co. epoxy I've heard of, but haven't tried. But that one is now at the top of my list to evaluate, given your descriptions of it.
Am also looking forward to hearing any thoughts you might care to share regarding what you've done to control thermal transfer with historic windows. I think these fenestration issues are really important ones for energy efficiency and establishing a good thermal envelope in an older home. And there is no need for apologizing for a delay. There is no time limit here for replying. I am glad that you invested so much time in providing us with a highly compreshensive and very useful report. And if there is any help I can provide you with regarding finding your way around the blogosphere, etc., please do not hestitate to ask. Thanks!