I’m replacing my picnic table and benches and wondering if I would benefit from constructing them using composite decking materials versus pressure treated pine 2×4’s.
One consideration would be of cost and the other is how well does the decking work with joiners, table saws, and power miter saws. Not having worked with these materials do they also require any special materials for connectors. For example when the new PT pine came out, and due to the different chemicals used to treat the pine, it was strongly suggested to use special screws without the zinc metal. Should I use stain or paint to finish the pieces?
Has anyone had any experience that they’d like to share to aid in my choice of materials?
Thanks
Senor Dorado
Replies
The composite deck materials aren't very stiff, so the design would have to allow for more supports for benches and top than typical picnic tables. For that matter I'm not at all sure they even come in 2x sizes--they are generally just the surfaces on decks where the structure is made from PT lumber--and with closer joist spacing to boot.
Steve's right about composites. They have very little stiffness and require more bracing than with solid wood. I wouldn't rule them out though, if you can tolerate the look. Most composites are just a plastic/wood fiber mixture. They machine fine with your regular power tools. Some compostites have a special "invisible" fastening system which engages in the slots in the sides of the boards. However, for your needs, these are not practical. You should look for decking that looks like regular lumber - without any grooves on the sides (bottom is okay).
Pressure treated lumber does a number on regular fasteners. Stainless steel is the best way to go.
I'd go with stain. If you like the solid colour of paint, go with a solid colour stain. Stain doesn't peel like paint.
Chris @ www.flairwoodwork.spaces.live.com
- Success is not the key to happines. Happiness is the key to success. If you love what you are doing, you will be successful. - Albert Schweitzer
Go with PT pine, it's much stronger and will last forever. I build and sell outdoor furniture of all kinds. I use mostly cypress because that seems to be what the customers want however I try to talk them into PT pine because it last longer and is stronger than cypress. I have used both stain and paint. Paint seems to work better. Be sure to let the wood dry good and seal it with a good oil base primer and top coat it with a good latex acrylic or oil base paint. Stainless screws are best but costly I've had good luck with the coated deck screws however and they are not expensive.
ZABO
i built a picnic table for a cafe in 2000 using trex for the top and seats and 2x4 spruce for the framing. it's still in great shape, despite the abuse, and to boot, weighs about 400 lbs, so nobody's ever tried to steal it.
PT ONLY for legs of the table. The sawdust is still toxic, so it's not good for your garden or your lungs. DO NOT burn the scraps either. Even though the formulation of PT has changed, it is still not good for general use around people. When I build a deck with the composite 'wood' the joists are on 12 inch centers, not 16 because the stuff is too flexible. If it's out in the sun, that table top will get nice and hot. You may want to look at IPE, it's almost totally rot and insect-proof. It is heavy and you will need to pre-drill all the screw holes. It will grey up a bit from the sun, but a coat of boiled linseed oil keeps it looking good for many years.
Our local State park replaced almost a mile of boardwalk with IPE and it has held up beautifully for over 3 years.... salt-water, sun and thousands of people, winter snow and wind-blown sand have not caused any degradation to the wood. The pine?? fir?? they were using lasted only 3 to 4 years before it had to be replaced.
Oh yes, they don't tell you this, but many of the composite woods will change color from sun exposure, so the nice dark brown becomes a medium brown after a season or two.
Sawdust Steve Long Island, NY (E of NY City)
Thank you all for your suggestions and advice. I'm off to Lowes to start pricing the materials. I'll get back to ya when I'm finished. Senor Dorado
If you can avoid the borg I'd do it. Real lumberyards quite often have much better lumber, for prices not much more.
As others have noted, the composites aren't strong enough. When used as decking, they require that the joists be on 12" centers -- real PT lumber can span 16".
Senor,
A couple of things to add:
1) If you use PT - LET IT DRY OUT before doing anything with it!
PT is usually still "wet" when you get it at the supply stores.
If you buy NOW and cut and assemble NOW - your project will
shrink as the lumber dries. Your joints will pull apart and the
end result will be an unstable table. (I speak from experience -
I have a garden gate I have to rebuild for this very reason).
2) I can't speak for stain - but if you opt to paint the tables
you should (again) let the wood dry for a year before painting.
Painting "wet" PT will result in poor adhesion & you'll never really
get a long lasting finish.
Best advice - be patient and let the wood dry.
Bill-
http://www.franklinwoodwright.com
Edited 8/19/2008 6:56 am ET by Woodrat1
I understand your concern and fully agree on the drying issue. Next problem that usually arises though is the bending, twisting, and cupping of the lumber. Unless you are very vigilant in stacking with stickers and rotating your stock. Especially with impregnated PT pine. Would you know the amount of time it takes to dry out 2x4x8' pt pine? I once had 50 1x8x9' poplar boards that took about 9 months to stabilize within my cellar, that had a dehumidifier running 24 7. Is there a better method to acclimatize? Keep a cool Breeze! Senor Dorado
Senor,No well defined answer to your question re: drying time.
Depends on how "wet" the PT is that you buy & how & where
you dry it - along with humidity levels in the storage area.You could use a moisture meter to check - or just good ol'
intuition to determine when the wood is ready to be worked.With PT - I just use intuition. When it feels light enough in weight
to match untreated wood - I use it. Being PT and the application
it's used for, I don't worry over it too much as I would a high
end project.Bill-http://www.franklinwoodwright.com
You can buy PT lumber that has been kiln dried after treatment so that it would have a considerably lower moisture content (under 19%--still not like the 6% - 8% range for furniture hardwoods.) You would have to pay for the convenience, making other good outdoor woods more feasible as alternatives.
I generally keep some pt lumber stored for future projects. I keep it stored flat, not necessarily stickered, in the attic of a storage shed. The shed has a metal roof and here in South Louisiana it gets pretty hot in there. I guess you could call it a solar kiln. But whatever it works for me. If I know I have a project coming up and I don't have enough dry stuff I buy what I need plus a little more to account for loss ( cupping and knots and such). I let it dry for a month or so and go ahead and use it. I have never had any problems with a project coming apart. As long as you screw and glue it good I don't think you will either. Like I said in an earlier post make sure the wood is dry before you apply any type of finish. I don't use a moisture meter for outdoor projects they are exposed to the weather anyway. You can usually tell when it is dry enough to paint by feel.
ZABO
One comment about Trex (and other brands of composite wood) - they're not quite as maintenance-free as their advertising literature would have you believe. In addition to sun-fading of the pigments that other posters have noted, leaves, acorns, and tree limbs will stain the material if they're allowed to sit on the decking (and especially if they get wet).
From the standpoint of building a deck with wet PT wood - it's very true that the decking will shrink, leaving gaps between the boards. However, this is what you want. If you thoroughly air or kiln dry the wood and butt the flooring together, there will be an insufficient gap between the planking to allow water to drain quickly. It will, of course, drain quite quickly in the beginning, but the very small chinks between the boards will quickly fill with dirt and muck, and water will sit on the deck, which is not a good thing from both the perspective of walking through puddles and the longevity of the deck boards.
Thanks guys. All real good info. I'm on it! Keep a cool Breeze! Senor Dorado
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