Filed Under (Knowledge) by Mason Pan on August-9-2008

Marine plywood is the premium quality exterior plywood . In order to understand marine plywood well, it’s better to make a comparison between marine plywood and general exterior plywood .

The following is the comparison between marine plywood and general exterior plywood :

1. The glue
The glue for marine plywood should be the best permanent WBP(phenolic) glue . But there are more types of WBP glue for general exterior plywood .

2. The grade of solid wood face/back veneer (see *Note 1 in the end of post)
No defects (except sound pin knots) are allowed on the face/back of marine plywood . But some defects are allowed on the face/back of low grade (such as C/D grade) general exterior plywood .

3. The thickness of solid wood face/back veneer
For marine plywood : According to marine plywood standard BS 1088 , the thickness of face/back veneers for multi-ply construction should be 1.3 ~ 3.8 mm; for three-ply construction, the thickness should be about 0.5mm .
For general exterior plywood: The thickness of face/back veneers can be reasonably thinner for cost-saving .

4. The core veneer
For marine plywood : Usually, each core layer of long grain should consist of only one piece of core veneer . Edge joints are allowed . End joints are prohibited . 
For general exterior plywood: Each core layer can consist of several pieces of core veneers . Both end joints and edge joints are allowed .

5. The species of wood
For marine plywood : The species should be hardwood of high density .
For general exterior plywood: The species can be hardwood of high density, MLH (Mixed Light Hardwood) and so on .

6. The application 
Marine plywood is intended for boat-building or other marine applications, aircraft construction . Marine plywood can also be used in construction. Marine plywood can be used for all the jobs which can be done by exterior plywood .
General exterior plywood is intended for indoor or outdoor application where resistance to weather/water is required .

Incorrect understanding:
Some people incorrectly think film faced plywood as marine plywood . In fact, the inner quality of marine plywood is much better than that of general film faced plywood . Marine plywood and film faced plywood have different meaning .

*Note 1 :
The face/back of marine plywood can also be MDO, HDO, or other weather/water resistant film paper .

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(9) Comments    What next?

Comments:
au****** on August 30th, 2008 at 1:48 am #

dear sir,
would any of the WBP type be able to pass the new Formaldehyde emission standard EO in USA?

Mason Pan on August 30th, 2008 at 5:25 am #

The best WBP (phenolic) glue type can pass that standard .

gea****** on March 10th, 2009 at 1:34 pm #

how much is a 8′ by 4′ foot marine ply wood for boats a sheet ?

Bru****** on May 20th, 2009 at 3:47 pm #

I am about to purchase a house in New Hampshire that was recently completed after spending 8-10 years as a shell, with a roof but not with siding.
Is the plywood sheathing OK? Or is it apt to be deteriorated by the weather.
How can I check it?
Thanks

CIn****** on May 27th, 2009 at 1:16 pm #

Can any exterior grade or marine grade plywood be used as vertical rain screen on a structure? How would the ends need to be treated?

Mason Pan on June 5th, 2009 at 1:04 am #

As far as I know, US people use structure plywood and structure OSB as sheathing materials . But the outsides should be covered with some water-proof materials, too . Please consult with a construction company because they are more professional on this matter .

Mason Pan on June 5th, 2009 at 1:08 am #

Structure plywood and structure OSB can be used as sheathing materials . But the outsides should be covered with some water-proof materials, too . Please consult with a construction company because they are more professional on this matter .

aja****** on September 13th, 2009 at 7:03 am #

thanks for information given on marine plywood. please send more information on plywood manufacturing and industry. with regards

aru****** on May 15th, 2010 at 7:27 am #

I want to use marine ply for my modular kitchen. how it will be and what is the usual cost of marine ply per sq feet/ meter.

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