In the Collins COBUILD English Dictionary*, "wood" is listed as a noun but not an adjective. According to their usage, then, the phrase "wooden bench" would be acceptable, while "wood bench" would not.
Similarly, in the Collins COBUILD online**, there are no occurrences of "wood bench." There are a few with "wooden bench," however:
"...went over and sat on a wooden bench against the cold stone wall. He was
...and each stood in front of a wooden bench behind the pulpit. The assistant
...The usual place was wooden bench beside the tranquil river in the...
...the-wall and sat on a scarred wooden bench bolted to the floor. One ..."
There are several more.
The American Heritage Dictionary of the English Language**, however, does list "wood" as an adjective, with these definitions:
"adj.
1. Made or consisting of wood; wooden."
So, using this dictionary as the standard, "wood bench" is perfectly acceptable.
About other collocations with wooden/wood, according to the Collins online site:
wooden floor 40
wood floor 4
wooden house 5
wood house 0
wooden furniture 4
wood furniture 4
As for the number of instances of "wooden bench" that appears on Google, when a search for that phrase is entered, it is 22, 400. In contrast, the number for "wood bench" is 8,930.
When you refer to the beams in an old house, you'd say the "wooden beams," right? And to the doors of an old building: "wooden doors." But if you were buying a new house and putting things in it, you'd probably say: "We're putting in new wood doors – we don't like the old metal ones." And, "We're getting all new wood bookcases – we don't like the composition ones." It feels like the old, established articles are "wooden," but the new ones, the ones that you acquire that aren't antiques, can be "wood."
"Wooden bench" appears far more frequently than "wood bench." But on the first two pages on Google, the sites are mostly catalogues, offering both "wooden benches" and "wood benches," in equal numbers. If I were going to an antique store, I'd be looking for a "wooden bench," but if I were buying sleek, modern furniture, I'd ask to see a nice "wood bench."
It may be that the old/new distinction also applies to woolen/ wool, golden/gold and other adjectives. I'll do some research on this and add to this posting.
Rachel
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*The Collins COBUILD English Dictionary. Harper Collins 1995
**http://titania.cobuild.collins.co.uk/form.html
***The American Heritage Dictionary of the English Language. Houghton Mifflin.1996