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Solution for exterior laminated member


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A local House of Worship has asked me to help with an issue involving one of the laminated wood beams that support the roof of the structure. It's the only one installed outdoors and is delaminating.

I've determined that wide moisture-related expansion/contraction cycles compounded by the curve in the beam and perhaps involving a type of adhesive not intended for exterior environments is causing the failures in the bonds. Not having the $52K is would cost to replace it with an engineered steel equivalent, they've asked for a more economical solution that would prevent further damage as the existing beam remains able to serve in my judgement. There is no rot at all in this beam. The failures are confined to the bonds between the laminations.

What's needed is a cladding that breathes, tolerates relative movement where the bonds have broken and has a drainage plane so that incidental moisture can escape. The moisture content of this beam must be stabilize and remain as dry as possible. It was previously painted but the shifting laminations crack the paint coating as soon as it dries. Water then enters with evaporation now virtually stopped by the paint.

Behind this beam is a wall of double wythe of brickwork (painted white). All of the interior beams are in perfect condition. I estimate the building as roughly 50, 60 yrs old. Most of the members of this community are long-time friends of mine and trust me completely. I've met a lot of their maintenance/service needs for nearly two decades now.

Any ideas? I thought of 3-coat traditional stucco w/drainage for the vertical surfaces of the beam but I'd like suggestions.

Marc

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A general caveat and a hard rule....

1) Avoid church work.

2) Never work for your own church.

Yeah on the stamped part, sort of, but in our experience, engineers always come up with the most cockamamie ideas imaginable.

Got a close up pic? I don't know which beam you're talking about. We did one where we simply capped it with an offset horse collar flashing. Copper. Ended up looking like an architectural detail. Cheap. Moisture equalized out from under the copper just fine.

That might not work in this case because I don't know which beam you're talking about.

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The beam is the blue-ish arch from left bottom corner to the underside of the roof deck to the right bottom corner. It's built from 2X6s, sanded to 5 inches thick. The rafter tails are separate and are attached with screws to the main arch.

Found some pics from my examination:

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Do you still think copper is an option?

Moving the brick wall is novel and ingenious. The cost would likely be prohibitive though.

Marc

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The wood member lasted 50 to 60 years. The steel won't last any longer. Replacing it in kind would likely be cheaper.

There's close proximity but no connection between the beam and the brickwork so why is it you don't think steel would last any longer?

Marc

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Steel, primed and coated with a rust inhibitor, would last longer than anyone would care about.

Expensive.....replace the entire thing, wood or steel, doesn't matter. Total ****ing mess on every level.

Cheap....wrap it in metal, details for drainage, drips, etc. Copper if you got the dough, aluminum if you don't. It'll dry out and be fine. If it's lasted this long in the LA climate climate with only this much delam, it'll last wrapped.

I'd pay close focus on the base so it doesn't wick; gotta isolate the base from wicking. I'd soak the thing in Abaton.

The largest problem is it's a church. My #1 business rule is never get between anyone and their obsessions.

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What is 'compression set'?

Marc

The outer fibers of the wood (let's say 1/4" to 1/2" deep) expand and contract a lot in your horrible climate. With a large assembly like that, as the wood tried to expand, it doesn't have enough room to move as much as it wants to, so the fibers become crushed. When the humidity drops, and contraction happens, the crushed fibers remain crushed, resulting in gaps. You've seen it where wood flooring gets wet - the wood expands to the point where it crushes. Then when it shrinks there are gaps.

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I think so too. I doubt it's delam'ed.

I don't think you even have to cover it with metal. If it was fully delaminated, those things look ridiculous.

Determine if it's actually delaminated, then figure out where to go. It doesn't look all that bad to me.

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Steel, primed and coated with a rust inhibitor, would last longer than anyone would care about.

Expensive.....replace the entire thing, wood or steel, doesn't matter. Total ****ing mess on every level.

Cheap....wrap it in metal, details for drainage, drips, etc. Copper if you got the dough, aluminum if you don't. It'll dry out and be fine. If it's lasted this long in the LA climate climate with only this much delam, it'll last wrapped.

I'd pay close focus on the base so it doesn't wick; gotta isolate the base from wicking. I'd soak the thing in Abaton.

The largest problem is it's a church. My #1 business rule is never get between anyone and their obsessions.

No wicking here. That's why I selected a location close to the foundation. There's not a spot of rot anywhere. So it looks like paint remover, light sanding, boiled linseed oil, drainage plane then wrap in aluminum. Folks will steal copper here. Someone drained the refrigerant from one of the AC's (R-22) last summer.

Twice I've had to sue in small claims a church. Both paid up the day before the court date. These folks here, I've served hundreds of times over nearly two decades without ever the slightest issue. Check out them Bahai's, I'll bet they would make good neighbors.

I appreciate all the suggestions. Thanks.

Marc

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Agreed on the Bahai's......this place is about 10 minutes from my house. It's peaceful, and it's beautiful. Click on the history link...built from white portland and crushed quartz crystal....it's incredible.

https://www.bahai.us/bahai-temple

Looking at it more, I don't even think you need to wrap it in aluminum. I'd forget boiled linseed; it breaks down. I'd coat the thing in plastic of some sort, probably epoxy, and paint it again. I don't think it's bad; it just needs love. I've seen similar stuff where it looks like total hell, but it still passes an engineering review.

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The outer fibers of the wood (let's say 1/4" to 1/2" deep) expand and contract a lot in your horrible climate. With a large assembly like that, as the wood tried to expand, it doesn't have enough room to move as much as it wants to, so the fibers become crushed. When the humidity drops, and contraction happens, the crushed fibers remain crushed, resulting in gaps. You've seen it where wood flooring gets wet - the wood expands to the point where it crushes. Then when it shrinks there are gaps.

That's good news if you're right.

This epoxy coating Kurt speaks of...I've found epoxy paints that are intended for steel and concrete substrates, but not for wood.

Marc

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That's right. Boats. And it's not paint, it's either injected or soaked into the wood in dilute form. And I'm not convinced it even needs that the more I look at the pics. I'd be doing some probing, drill a few small holes, and looking deeper before I decided anything.

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The outer fibers of the wood (let's say 1/4" to 1/2" deep) expand and contract a lot in your horrible climate. With a large assembly like that, as the wood tried to expand, it doesn't have enough room to move as much as it wants to, so the fibers become crushed. When the humidity drops, and contraction happens, the crushed fibers remain crushed, resulting in gaps. You've seen it where wood flooring gets wet - the wood expands to the point where it crushes. Then when it shrinks there are gaps.

That's good news if you're right.

This epoxy coating Kurt speaks of...I've found epoxy paints that are intended for steel and concrete substrates, but not for wood.

Marc

Clear Penetrating Epoxy Sealer by Smith & Company is made specifically for wood and make an excellent primer for paint. I've used gallons of it over the years. I believe we've discussed it here before and the mad scientist who makes it even stopped by to discuss it a while back.

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The outer fibers of the wood (let's say 1/4" to 1/2" deep) expand and contract a lot in your horrible climate. With a large assembly like that, as the wood tried to expand, it doesn't have enough room to move as much as it wants to, so the fibers become crushed. When the humidity drops, and contraction happens, the crushed fibers remain crushed, resulting in gaps. You've seen it where wood flooring gets wet - the wood expands to the point where it crushes. Then when it shrinks there are gaps.

That's good news if you're right.

This epoxy coating Kurt speaks of...I've found epoxy paints that are intended for steel and concrete substrates, but not for wood.

Marc

Clear Penetrating Epoxy Sealer by Smith & Company is made specifically for wood and make an excellent primer for paint. I've used gallons of it over the years. I believe we've discussed it here before and the mad scientist who makes it even stopped by to discuss it a while back.

I contacted him within the last few months. He sent info about wood restoration but he'll sell product to me only in large quantities, like 5 gal pails or larger. There are no local vendors. I've been checking out Albatron.

Looks like what I need is a low viscosity epoxy product for the gaps and a higher viscosity version for subsequent roller/brush application.

Breaking a lot of new ground here. Never used or even seen epoxy paints before.

Marc

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I don't think you're necessarily looking for a paint. You (probably) want a penetrating epoxy sealer. Thin epoxy is one of the most aggressive penetrants there is; it goes deep. Paint it with whatever is compatible with the epoxy sealer.

I use WEST system because I can get it in quarts or gallons (don't buy too much, epoxy has a shelf life) from Amazon, and they have a very nice metering pump system. Everyone should have at least a quart on their bench, w/pumps, and some microfiber or micro balloons for fairing out and filling stuff. I've still got a bag of Cabosil, and I make structural putties with it. I cut with lacquer thinner to whatever viscosity I'm looking for to use as a sealer.

Smith may be "the best", but you'd have a hard time convincing the tens of thousands of other system users. Steve is a little weird, claiming to have "invented" a process where a lot of practitioners were all on the same parallel path with regards to wood restoration. All the things he claims only his material does, I've done with WEST, Abatron, and plain old epoxy out of a tube from Ace Hardware.

It's not complicated. It's more about process, temperature, proportions, and understanding the materials you're working with than a specific epoxy imho.

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Ok. I've got in my shopping cart West #105 resin and #207 clear hardener. Kit comes with pumps, etc. Elsewhere is a small bag of Cabosil for raising the viscosity of the epoxy mix enough to fill vertical gaps.

Am I in the ballpark?

Marc

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Counterintuitive note.....

More hardener makes things gooier and less hard. Less hardener makes them more brittle. The spec'd proportions coming out of the pumps are pretty darn good, but you can tweak it a little here and there depending on what you're doing.

Don't make the big mistake of mixing too much at one time in a deep cup; the stuff is exothermic...gets damn hot in a cup. If you mix a large patch, you want to spread it out on a cookie sheet covered in wax paper so the heat dissipates.

Heat makes it set quicker, so when it starts warming up, you are being notified you need to spread it out to dissipate the heat.

It just takes a little practice. It's not complicated.

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