Requirements concerning Duobalken® and Triobalken®

The specification of quality criteria which exceed those required by building regulations were first defined in 2003 in an agreement on Duobalken® and Triobalken®. To minimize cracking and deformation from shrinkage caused by drying, specifications for moisture content and the type of cutting were set down. Other criteria are concerned mainly with the dimensional stability and the appearance of the timber.


The table below comes from the revised Agreement on Duobalken® and Triobalken® from 2015. It can also be applied to the laminated beams according to EN 15497, until revision of the agreement.

Requirements to be met by Duobalken® and Triobalken® in accordance with the National technical approval of the German building authorities as assessed by the Deutsche Institut für Bautechnik Z-9.1-440 and the agreement on Duobalken® and Triobalken®




Exposed areas (Si)

Non-exposed areas(NSi)

Technical Approval

Z 9.1-440



Grading class

S10 TS or
C24M according to DIN 4071-1 or C24 acc. to DIN EN 14081-1 and DIN 20000-5

The characteristic strength, stiffness and density values of laminations with the lowest strength class in the cross-section, apart from C24, where E0,mean is E0,mean=11.600 N/mm²
Other strength classes are available on request

Moisture content

max. 15%

Prerequisite for bonding

Dimensional stability
of the cross-section

DIN EN 336, Dimensional stability class 2
w ≤ 100 mm   ± 1 mm
b > 100 mm ± 1,5 mm

The dimensional stability for the longitudinal dimensions must be agreed between the customer and supplier.


≤ 4 mm/2 m

For comparison:
DIN 4074-1; S10: ≤ 8 mm/2 m

Longitudinal warping

≤ 4 mm/2 m

In comparison:
DIN 4074-1; S10: ≤ 8 mm/2 m

Surface condition

Planed and chamfered

Leveled and chamfered

The "right" sides (near-core sides) must face outwards

Finishing of the ends

Trimmed perpendicular