Wood for ground contact laminated beam
DonStephan
| Posted in General Discussion on
I’ve been asked to bid on laminating 18″ x 7″ x 8′ beams for a bocce ball court. The beams will be on concrete footers. The court is about 10″ lower than the surrounding lawn so the bottom and much of the outside will be coated with epoxy paint and below grade. The court will be sprinkled daily to maintain the clay court surface. The top edge of the beams will be covered with aluminum or copper cap.
Anyone know a source for kiln dried treated lumber? With a dark deck stain that wood would look good enough. As another option, anyone have any experience with marine plywood in contact with the ground? The front face of this would have to be covered with a 1/2″ mahogany or similar board for appearance.
Thanks.
Replies
Sounds like a poorly though out design but that isn't your problem. They should just cast the entire beam out of concrete and then trim it out with wood and copper faces as needed
The quickest way to do this would be to rip 3/4 " PT plywood into strips and then stack them up to get the beam. I'd use glue and stainless steel screws to attach each layer to the one below so there would be no need to use clamps. Marine plywood isn't treated to resist rotting it would be useless for this job.
John White, Shop Manager, Fine Woodworking Magazine
JWW, don't you know that a serious BOCCE court is a little more than another FWW design by the numbers /science available project. If those balls do not bounce from the walls on that dampened clay in the "accustomed" way, you all may have to go into hiding. This all depends on who the client is. Check it out, a great deal of green will change hands in games on a court(of course amongst friends?) Pat
BTW, ya think I got my moniker at Yale? How about South Brooklyn , AKA the Irish kid on the Bocce court. pfh
Sounds like a good job for composite lumber.
Jack
You can find ACQ pressure treated that has been kiln dried after treatment--if you have a real lumberyard that caters to high end custom builders. If you were in CT I know exactly where to send you.
How about this. When pouring the footer add an above grade square shape of concrete about 10 inches tall and 4 inches square. Inside that square imbed pvc pipe to allow thru bolts to be inserted after the concrete dries. When you build the beam shorten the inside laminations by 10 inches and extend the outside laminations to go near the ground but not touch the groung ( with a 7 inch beam and 4 inch concrete that would be 1 1/2" of thickness of outside lamination on all 4 sides.Remember it is still a solid beam .When installing the beams countersink the thru bolts,but only to the depth of the bolt head so you don't weaken the wood too much. Cover the bottom section with a base board that covers the bolts and goes to the ground. The only part of the beam that will be subject to rot will be the baseboard and that can be replaced without compromising the beam.
Thanks everyone for the very helpful replies. I was surprised to find that the laminated beams are specified in great detail in the official rules; the customer has said the beams have to match the specifications exactly.I'll check on a Cincinnati source for kiln dried treated lumber and kiln dried treated plywood, which I had overlooked.Thanks for answering my question about marine plywood John. I'll let the customer know that's not an option.The option with PVC is very good, but unfortunately here the beams have to comply with the official specifications.Don
If the beams are covered by specifications there are probably a few more specifications about wood type and other details. You should get a copy of the official requirements before going too much farther with this.
I would also suspect that there is somebody out there already manufacturing these beams, a Google search will probably turn them up and you can get some hints about how they build their beams from their web page. If they are doing this as a business they have probably worked out a method of making a sturdy product efficiently.
John W.
I totally agree with you, John.
One possibility that would probably not rot though, is to use Black Locust. It is as rot proof as wood gets.
The keel of the USS Constitution (Old Ironsides) was made of it and was the only part with no rot found when it was rebuilt a few years ago.
This wood also makes great fence posts. But you have to put them in the holes upside down or they will start to grow.
Hal
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