SUMMARY OF CHARACTERISTICS AND ALLOWABLE DEFECTS FOR BACK GRADES

Grade Description

1

2

3

4

 

(Sound, same species, specify cut)

(Solid, same species, specify cut)

(Any solid back, other species)

(Reject back)

 
Sapwood

Yes

Yes

Yes

Yes

Discolouration & Stain

Yes

Yes

Yes

Yes

Mineral Streaks

Yes

Yes

Yes

Yes

Sound Tight Burls

Yes

Yes

Yes

Yes

Sound Tight Knots

Max. Diameter 3/8"

Max. Diameter 3/4"

Max. Diameter 1 1/2"

Yes

Maximum Number of Tight Knots

16

16

Unlimited to 1/2";

No more than 16 from 1/2" to 1 1/2"

Unlimited

Knot Holes

No

3/8" Repaired

1" Repaired

3"

Maximum Combined  Number of Knot Holes and
Repaired Knots

Nonea

All Repaired;
Unlimited to 3/8"

Unlimited to 3/8";

No more than 10 from 3/8" to 1" - Repaired

Unlimited

Wormholes

Filledb

Filledb

Yes

Yes

Splits or Joints

Six 1/8"x12"
Repaired

Six 3/16"x12"
Repaired

Yes 3/8" by 1/4 length of panel
Repaired

1" for one-fourth length of panel;
1/2" for one-half length of panel;
1/4" for full length of panel.

Doze & Decay

Firm areas of doze
No decay

Firm areas of doze
No decay

Firm areas of doze
No decay

Areas of doze and decay provided serviceability of panel is not impaired.

Rough Cut

Two 8" areas

Yes

Yes

Yes

Ruptured Grain

Slight

Some

Yes

Yes

Bark Pockets

1/8" wide - Repaired

1/4" wide - Repaired

Repaired

Yes

Laps

No

Repaired

Repaired

Yes

Back is the unexposed surface of a panel, or the second (least important decorative) surface when both surfaces are exposed. A back grade may be ordered for both surfaces when agreed to by both buyer and seller.

a Repaired pin knots allowed.

b Unfilled, inconspicuous, vertical wormholes not larger than 1/16" in diameter are permitted.

 

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Horizon Plywood.