plywood question

I have loads of different grades of Ply ... anybody know of a good on-line source that helps identify different standards for ply.
For example I have 1/2" ply .. in shuttering grade, WBP and Marine .... understand the difference OK, but I also have some 1/2" ply that is made from more individual plys than 'the standards'
It is very good quality, very dense and seems to be generally referred to as Birch ply ... but I assumed Birch was referring to finish on one face only. ?
Any Ply experts want to enlighten ?
Rick
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On Sun, 9 Nov 2003 21:27:56 +0000 (UTC), "Rick Hughes"

WBP and marine, not since the machines making the sheets got better. THe marine ply has to have BS1088 ??? stamped on the edges
You can also get drawer ply, which is all laminates go in the same way
also the wbp can come in brazilian (pale colour and quite light) or far eastern (coral to deep pink colour and can be quite heavy), the sheds tend to supply the inferior brazilian which can make them seem cheaper.
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Rick Hughes wrote:

Birch ply is ALL birch IIRC. Its excellent stuff. Its NOT fully waterproof, but apart from that its the best.
Marine ply uses a fuly waterproof glue. Top line stuff usually.
I'd use the birch for gerenarl work, and marine on e.g. bathroom floors and splash panels.
General purpose ply is OK for riough work - house cladding under a render coat etc.

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wrote:

the glue lines are identical.......(both have 'water-boil proof (72h) glue lines)
(marine is a subset of the wbp exterior grade)
The main criteria for this BS1088 is that there are no core gaps in the laminates (which the well made 'wbp' dont have nowadays). And that there is a smooth face and near smooth back (smooth defect only allowed), which good wbp grades have anyway. Finally all exposed edges should be sealed to retard the ingress of water
Marine is way overkill on bathroom floors wbp is easily up to the job, and once people know the price difference 99/100 wbp is used.
i quote from a website 'Marine plywood is sought after for its structural qualities but contrary to popular belief, it does not necessarily have any natural resistance to rot or decay if exposed to wet or damp conditions'
I have some people wanting marine for shed roofing ............

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