Decks, Patios, Porches and Docks - Composite Decking

I'm considering using composite decking for my boat dock. Can this be used in this application, and if so how durable is the product. Can it placed in the water
and continue to be structurally sound?

A dock is an excellent application for either composite or vinyl decking. But what would you be placing IN the water? Neither a composite nor a vinyl can be used as part of the structure (framing).

One thing that you would really want to check carefully is how slick is the product you are looking at when it's wet. I have looked at a couple of vinyls that are slippery when wet. One that ISN'T is Pro Cell.

Lefty, what I was intending to say was when waves and such constantly pound on the material. Is is it solid and holds up with water constently present. Didn't mean to indicate framing. Thanks

Vinyl is plastic and won't be affected by water. Composites are about 1/2 plastic and 1/2 wood fiber. Due to the way that it is made, at least 95% of the wood fiber is encapsulated by the plastic. Again, water isn't going to affect that either. My biggest concern would be 'how slippery is it?', and I would check that out thoroghly before selecting the brand of composite or vinyl to use.

i think a composite is great on a dock, especially one that is non slippery and have seen many used in my locale. virtually all products have an ADA approval for non-slipperyness (is that a word?). Anyhow the best test is to simply run your hand across them. Some are a heck of a lot smoother than others. let your hands tell you what is slippery and what is not.

about dos and don'ts: docks are often made with 2by material. a 2x6 for instance will span 24". Composite must be installed on 16" centers. a few claim to span longer, but i'd be wary of them. one that claimed 24" is (or was) Nexwood. They just threw in the bankrupt towel a few weeks ago. Hollow or corregated products are supposedly able to span longer. Nexwood was hollow, but that property led to other problems and their demise.

docks also usually have the 2x6 hanging over the side of the joist. you just cannot do that with composites. maybe an ince or two is maximum. this may mean redesigning your joist supports.

lastly, the above poster was right about composite being 1/2 wood, but depending on the manufacturing process some will are denser than others. the less dense products will absorb more water and may become water logged or grow mold. an important specification to check is the 24 hr soak test. the results will be expressed as a percentage. some brochures will omit the actual numbers and substitute words like "minimal" absorption. don't buy that crap. insist on an actual number that will let you compare objectively. other factors to check actuall numbers on are strength related.

a very good indication of composite applicability is whether others in your area have used it. ask the salesmen for references on a dock in your area.
By the way, if the salesman has no idea what you are talking about or tries to bluff his way through, run away from that store.

I built a dock a couple of years ago using TimberTech. It is built on pilings and has a welded steel frame. Treated lumber was bolted onto the steel frame, and the Timber Tech was attached to that. I used the T&G product. It has held up quite well over the past two years. You can see a picture here:

<IMG SRC="http://www.idcc.net/pictures/Dock06072004%20001-small.jpg" />

Thanks to all, couldn't of asked for a better response. The attached .jpg was great.