Plywood Guide: Grades and Uses

Plywood Guide: Grades and Uses

Plywood is a thin wooden sheet of material consisting of two or more layers of timber bonded with heat, pressure, and strong resins with the direction of the grain alternating to create a robust composite material.

There are several kinds of plywood which have different properties based on their manufacture and intended application. Here we will outline the defining factors in each grade, the finish and treatments that determine the different grades.

Plywood Manufacture

Four types of glue bonds are used for plywood manufacture, in decreasing order of durability.

  • Type A bond uses a phenol-formaldehyde resin which is specified for marine and exterior plywood and will not weaken under wet conditions, heat, or cold.
  • Type B bond uses a melamine fortified urea formaldehyde resin and is suitable for exterior applications including concrete formwork.
  • Type C and D bonds use urea-formaldehyde resin and are both interior bonds and are not recommended for structural applications.

Veneers

There are five veneer qualities specified as A, S, B, C and D in descending order. The face’s veneer grade is given first followed by the back veneer grade. E.g. Where only one face will show such as in wall cladding the veneer quality could be given as AD.

  •     A is a high-quality appearance grade veneer for decorative uses.
  •     S is an appearance grade veneer which allows more natural characteristics.
  •     B is suitable for high-quality paint finishing.
  •     C has a solid makeup and is designed for non-visual applications.
  •     D is a non-appearance grade explicitly designed for structural applications.

Strength and Stability

In plywood boards, the outermost veneer has a significant influence on strength and stiffness. An A or B grade veneer will increase a board’s engineering properties by one stress grade.

Cross-lamination of veneer layers restricts the movement across the grain due to moisture and temperature changes. Most structural plywood has more strength in the direction of the grain, and its recommended that the face grain of structural plywood should run parallel to the span.

Treatment

All timber products may be subject to decay and termite attack under certain conditions. Direct contact with the ground is exceptionally conducive to both decay conditions and termite attack.

Preservative treatment is essential for all wood products that are permanently exposed to the weather. There are several methods of treating plywood including;

  •     Impregnation of veneers before manufacture
  •     Pressure treating the manufactured product
  •     Treating surfaces after production

Treating surfaces after manufacture should be done only after machining, sawing and boring the plywood. If the plywood is cut, the surface treatment is required the cut edge.

Grades

Structural Plywood

Structural Plywood is suitable for structural applications as a Type A bond is used.Structural plywood comes in eight standard stress grades and five face veneer qualities.

In exposed applications, structural plywood must be treated to ensure its full-service life and to minimise checking.The product can be specified with the appropriate veneer qualities to suit the specified application.E.g. cladding can be manufactured to a higher quality AD or BD grade.

Structural Plywood features:

  •     Excellent damage resistance
  •     Allows nailing close to panel edges
  •     High Strength and Stiffness to Weight Ratio
  •     High Dimensional Stability
  •     Twice the shear carrying capacity of timber
  •     Chemically Resistant and non-corrosive

Interior Plywood

Plywood Guide: Grades and UsesSource: Lunchbox Architect

Interior plywoods are intended for use in non-structural application where a high-quality aesthetic finish is required such as interior wall panelling and fitments but must not be used in exposed, wet or damp conditions.

A grade faces should be used where a clear finish is required B grade faces can be determined where a standard paint finish is planned.

Interior plywood will have either a type C or type D bond. Type C should be used in higher humidity environments such as bathrooms or the tropics.

Interior Plywood features:

  •     Works without sophisticated equipment
  •     Allows nailing close to panel edges
  •     Can be glued with normal wood adhesives
  •     Variety of finishes for a decorative appearance
  •     Natural beauty
  •     Versatility

Exterior Plywood

Exterior plywood is intended for use in non-structural, exterior application where a high-quality aesthetic finish is required. Typical applications include signs and non-structural claddings.

Exterior plywood is manufactured with a higher quality(A, B, or S grade) face with a reduced quality (C or D grade) back.

Exterior plywoods possess either a permanent Type A bond or a less durable Type B bond. All exposed exterior plywood should be treated to guard against fungal attack.

Exterior Plywood features:

  •     No fear of delamination
  •     Dimensional stability under moisture changes
  •     Easily finished
  •     Works without sophisticated equipment
  •     Allows nailing close to panel edges
  •     Versatile

Marine Plywood

Marine plywood is a purpose-built structural plywood with a permanent Type A bond. It is intended for use in hulls of boats and other marine applications.

Marine plywood is made from selected species and therefore has known and consistent structural properties. The assigned stress grade is F14 and is manufactured with two A grade veneer faces.

The product can be painted or clear finished on both surfaces and provides an excellent base for paints, varnishes, and high gloss finishes.

Marine Plywood features:

  •     High strength and stiffness to weight ratio
  •     High dimensional stability
  •     High shear and chemical resistance
  •     Works without sophisticated equipment
  •     High impact resistance
  •     Paintable

Plywood Suppliers

Austim carries a range of plywood, timber and composite products. Contact Austim directly with any questions or technical enquiries.

Share on facebook
Facebook
Share on twitter
Twitter
Share on pinterest
Pinterest

Get a Quote or Enquire

austim book

Download product range price list

What our clients say

Austim are a great partner and timber supplier. Our business is based on the East Coast of Australia and we partner with Austim for WA projects. We have had a long lasting and great working relationship with Austim for many years. Highly recommend them.
daniel wright
daniel wright
06:31 18 Jun 19
Austim is always the first place I try when I need timber and it’s rare that I can’t get what I need there. Stuart is a rare gem of a gent to deal with – quick to respond to any queries, full of good advice and goes out of his way to help get whatever project I’m working on happening to my schedule, even when all I need is a few sticks and a handful of fixings. Highly recommend Austim, the team and young Stuart.
Anni Lilford
Anni Lilford
00:51 16 Nov 18
Stuart went out of his way to make sure we got the product we wanted. He made suggestions on possible constructions and timbers suitable. Very knowledgeable friendly staff all around. Excellent experience, highly recommended.
Holger Butenschon
Holger Butenschon
05:14 22 May 18
Hi Ben,Just wanted to thankyou for your help and advice in our selection of the Millboard Vintage Oak decking also in you recommending Grant from Premier Hardwood Decking. Grant has just completed our decking and we couldn't have asked for a more professional, reliable and competent tradesman. The decking has been installed to a very high standard and the decking itself is stunning. Ian and Sue
susan smith
susan smith
06:27 08 Oct 18
I've used Austim on a few occasions for home projects like decking and pergola, etc and each time the response to my requests for price and delivery have been excellent, the deliveries took place as negotiated, the timber quality was great and value for money. The team at Austim do a great job and make dealing with Austim a breeze.
Michael Robinson
Michael Robinson
09:06 25 Oct 18
I have worked with Austim for around 8 years now and they are one of the best suppliers in perth to deal with. I would highly recommend to use them for any timber needs!!!
Art of Timber
Art of Timber
07:55 05 Mar 20
I had been looking for some cedar for my kayak project and had rung a couple of other places with no luck. When I contacted Austim they were very helpful, had the timber in stock and I was on my was in 20 minutes. The wood was very good quality and has really finished up beautifully. Thanks to Austim.
mark alderson
mark alderson
02:03 08 Apr 17
I"d like to thank Austim for there help in supplying me with material that firstly I thought I'd have trouble sourcing as it was marring up with originally 30 year old existing timber.My project was not a massive project but still needed the attention of an new build.The timber supplied by Austim was machined to size with absolute perfection, where I had to remove old pieces and replace with the new pieces they fitted perfectly.once the floors are re-sanded and varnished they will be back to there former glory. Thanks again to the staff at Austim.Regards Bob Heppenstall.I've just added a finished photo after the Floor Sanding was completed.Original timber was Tassie Oak, and the new is Vic Ash, as you can see there is only a slight variation in the final product.I hope this gives anyone thinking doing the same the confidence to proceed. Regards Bob Heppenstall.
Robert Heppenstall
Robert Heppenstall
10:05 12 Oct 18
Great service over phone and by email. Product supplied is high quality - no issues. Staff accommodating and friendly.
M F
M F
00:18 07 May 20
Good service with fair prices.
Colin Della Bosca
Colin Della Bosca
08:14 04 Jun 20

Austim Inspirations

Request Price List

“The timber quality is excellent, the price was competitive, the communication spot on and the delivery just right. Well done and thanks again”

Michael

.