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Frequently Asked Questions

General

What is the difference between balanced and unbalanced glulam beams?

Glulam beams are typically designed with the highest quality laminations placed in zones of maximum expected flexural tension stresses. A somewhat lower grade can be used to resist flexural compression stresses with no reduction in beam capacity.

Consequently, lay-ups are divided into two categories: balanced and unbalanced (See figure). Balanced beams are typically used for continuous-span and cantilevered applications where both the top and bottom of the beam will be subject to flexural tension. Unbalanced beams are preferred for simple spans, because they use lumber resources more efficiently and are consequently more economical than balanced beams. Unbalanced beams can also accommodate short cantilevers (up to about 20% of the main span).

To avoid improper installation, glulam beams are distinctively marked with a “TOP” stamp. Protective wrappings on glulam beams are also typically stapled on the top face of the beam to avoid damaging the faces that will be exposed to view in the finished structure.



Unbalanced layups are optimized for simple spans, and balanced layups are optimized for multiple spans. Letters symbolize relative quality of laminations (A represents highest quality, C represents lowest quality in lay-up)

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Flexural Tension:
describes the tension forces or stresses occurring in a member due to the lengthening of one side of a member as it bends.
Flexural Compression:
describes the compression forces or stresses occurring in a member due to the shortening of one side of a member as it bends.
Balanced Lay-up:
A glulam configuration having the laminations arranged so that the same grades of lumber are used in the top half of the beam as in the bottom half. The two halves are mirror images of each other.
Unbalanced Lay-up:
A glulam configuration having the laminations arranged with higher grades placed in the bottom half than in the top half.