Marine Plywood quality

[Possom]

I'm trying to compare the quality of these two marine plywoods from two different suppliers. Is it possible to tell from the descriptions as to which is the better quality? That is, in terms of being water repellent.

Thanks.


Marine MTCS (PEFC) BS1088 part1 2003 Marine Grade CE2+ E1 EN636-3 EN314-2 Class 3


BS1088, KOMO Class ‘A’, ‘C’ and Lloyds certified. (Guaranteed 25 years)

 

[Roger928]

No idea.
Both will probably be bonded using exterior phenol glue. Same as the glue used for WBP plywood.
Genuine Marine plywood is normally used for the boat building industry or where the board is going to be in contact with water and moisture for a very long time.
And the ply's will be high quality hardwoods.
We use crap Chinese plywood which is supposed to be marine quality. (ie. Fit for underwater) Which delaminates easily.
Especially if the sawn edges are not sealed.
It looks whitish when sawn and not brownish as you'd expect if it contained hardwoods.

I've seen and used 3.3m x 1.2m x 18mm marine ply which costs £200.
It looks brown when sawn. You can tell the quality just by looking at the exterior face also.

 

[JohnD]

if it is genuine Marine ply (unlikely) examine the face. There should be no knots or cracks. look at all cut edges. There should be no voids. It should be stamped with the official grading (the term "marine ply" is no longer officially used). It costs in the region of four times as much as ordinary WBP ply. Ordinary timber yards are unlikely to stock it as it is so expensive, and unnecessary for most work. You would have to order it from a supplier that caters for the boat-building trade. You might find it more easily if you are somewhere like Southampton. It does not have a paper-thin decorative outer layer like "hardwood faced ply"

If it is Lloyds Certified then it should have been subject to third-party inspection and approval. I don't know if there should be a certificate you can see.

"Marine plywood
Marine plywood is manufactured from durable face and core veneers, with few defects so it performs longer in both humid and wet conditions and resists delaminating and fungal attack. Its construction is such that it can be used in environments where it is exposed to moisture for long periods. Each wood veneer will be from tropical hardwoods, have negligible core gap, limiting the chance of trapping water in the plywood and hence providing a solid and stable glue bond. It uses an exterior Water and Boil Proof (WBP) glue similar to most exterior plywoods.

Marine plywood can be graded as being compliant with BS 1088, which is a British Standard for marine plywood. There are few international standards for grading marine plywood and most of the standards are voluntary. Some marine plywood has a Lloyd's of London stamp that certifies it to be BS 1088 compliant. Some plywood is also labelled based on the wood used to manufacture it. Examples of this are Okoumé or Meranti."

https://en.wikipedia.org/wiki/Plywood#Marine_plywood

See also
https://en.wikipedia.org/wiki/BS_1088

I have a few offcuts in the shed.

 

[Possom]

Thanks very much for both replies. Some very helpful info there. Thanks guys.