Replies

1. 
   DanH | Aug 13, 2008 06:15pm | #1

   The biggest problem with composites in this context is that most aren't as stiff as the equivalent wood. You need to alter the design to assure that the whole thing doesn't fold up when several big adults sit down at the picnic table.

   It is an ironic habit of human beings to run faster when we have lost our way. --Rollo May
2. 
   McDesign | Aug 13, 2008 07:33pm | #2

   I agree - composites are just not stiff enough for a chair or table designed with wood in mind.  Plus, composites can "creep" - that is, continually deform under load - even a relatively small load.  That's why they can never be used in structural applications.

   Forrest

3. 
   kbd | Aug 13, 2008 08:08pm | #3

   You don't want to use pressure treated material as a table you will be eating off of. The old pressure treated had arsenic and chromate. Unless of course your having the in-laws over.

4. 
   MGMaxwell | Aug 13, 2008 08:25pm | #4

   If you pay attention to the consideration of structural weakness of the composites, then I think the composites make a good seating and table surfaces.

   They can be cut and shaped with regular woodworking tools. The will expand with heat but their distortion is less than what you will get with painted or stained treated SYP.

   I'm sorry but I've never given much thought to CCA or ACQ toxicity unless you're eating the sawdust and using treated lumber to make your dinnerware. Everything has a risk benefit ratio, and on my list of things to worry about, arsenic poisoning was further down the list than structural weakness from corroding fasteners. Of course other people have different risk aversion thoughts that are legitimate.

   There is no doubt the composites will last longer. Just think of no splinters and a nice smooth surface to sit on.

   If you are just making picnic tables and benches then the premium cost of the composites should not hold you back.

   I would choose one of the fancy colors rather than paint.

   This info is from a DIY, but I've built a dock, boat house, bulkhead and a large muliteared deck utilizing TREX for non structural components

1. 
   emaxxman00 | Aug 18, 2008 07:38pm | #5

   I've seen ~5ft long park benches made with composite material.  There are only the end and a single middle support.  These benches don't seem to flex at all when I'm sitting on them (200lbs). 

   The composite board seem to be more like a 2x4 in dimensions vs composite decking. 

   My understanding is that composite decking is also comparable to other more durable woods like redwood/cedar, etc.  I could be remembering that wrong.  I would check prices on those woods too...and they look nicer.

2. 
   Piffin | Aug 18, 2008 08:11pm | #7

   "arsenic poisoning was further down the list than structural weakness from corroding fasteners."That is true for building decks - but for eating surfaces or playground stuff that children chew on... 

    

   Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!

5. 
   Piffin | Aug 18, 2008 08:07pm | #6

   I don't know if you are referring to surfaces or framing, but I would never use PT for the surface lumber of an eating surface.

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

6. 
   Jim_Allen | Aug 18, 2008 08:13pm | #8

   My best tables were doug fir unfinished. The tops would last years and years and years.

   I noticed an interesting phenom on a table that I had that someone had finished with some exterior hard shell. The top finish broke down and blistered away in the sun. The bottom finish stayed. The wood rotted because the bottom finish acted like a container and held the water in down below.

   My unfinished tables out lasted the finished one by a wide margin. I could take out my plane and re-finish the unfinished table and make it look new in a very short timeframe. The protected table was mush.