For suppliers

Surface visual quality classes

Prepared according to recommendations of German Laminated-Wood Research Laboratory (Association)(Studiengemeinschaft Holzleimbau e.V.).

 

Special requirements or criteria (other, not specified below) are the subject of agreement between the supplier and the buyer, i.e., they are additionally stated in the specifications of the supplied product and descriptions.

 

Criteria       

Industrial quality    

Standard quality

    

Selected (extra) quality

 

1

Firmly grown knots 

 

Permitted

Permitted

Permitted

2

Fallen and loose knots with bark remnants 

 

Up to Ø ≤ 30 mm permitted, from Ø > 30 mm to be replaced in the works

Up to Ø ≤ 20 mm permitted, from Ø > 20 mm to be replaced in the works

Replaced in the works.

Not replaced in the works if up to Ø 5 mm in diameter.

3

Resin galls  

Delivery condition

Permitted

Up to 5 mm wide resin galls are permitted

Up to 3 mm wide resin galls are permitted

4

Faulty points improved by means of “ships” or knot hole plugs

Not necessary

Permitted

Permitted

5

Knots and cracks improved by means of filler compound      Number of improvements not limited

Not necessary

Permitted  

To be agreed with

the client

Permitted  

To be agreed with

the client

6

Insect attack, bore holes  

 

Burrows are permitted up to 2 mm

Permitted bore holes up to 2 mm

Not permitted

7

Pith

Permitted

Permitted

Pith not permitted in visible surfaces of external lamellas

8

Cracks caused by shrinking 

Delivery condition

Not limited

Up to 2 mm wide

Width – up to 1 mm

9

Discolorations as a result of blue stain, red and brown stripes  

Delivery condition

Not limited

Up to 10% of the whole structure component visible surface area

Not permitted

10

Mould 

Delivery condition

Not permitted

Not permitted

Not permitted

11

Contamination of the surface

Delivery condition

Not permitted

Not permitted

Not permitted

12

Distance between finger joints

Not limited

Not limited

Distance between finger joints of visible external lamellas min. 0.7 mm.

13

Surface

Unplaned areas are permitted up to 5% of the surface area if not deeper than > 3 mm

Planed, edges slightly chamfered. Planed chatter permitted up to a depth of 1 mm.

Planed, edges slightly chamfered. Planed chatter permitted up to depth of 0.5 mm. Surface can be polished by separate agreement.

14 

Grown in bark

Permitted

Width up to 10 mm, length up to 60 mm

Not permitted

15

Rip-outs

Permitted

Depth up to 2 mm, diameter up to 15 mm

Not permitted

 

NOTES:

 

1. The depth of the crack may be, independent of the visual quality class of the surface for structure components, for members not being subject to tensile-stresses perpendicular to the grain up to 1/6 of the width of the structure component, for members being subject to tensile-stresses perpendicular to the grain, up to 1/8 of the width of the component.

2. If visual surface quality class is not specified in the order, products of standard surface quality are supplied.

Compared with solid wood, glued laminated timber is mainly a crack-resistant wooden material. Cracks on the surface caused by changes and fluctuations in the climate or environment are inevitable. Thus, they are not a considered a defect and are permitted and have no impact on strength of the structure component.