AITC Technical Note 11, titled “Checking in Glued Laminated Timber,” provides guidelines on the significance of checking glued laminated timber members.
In general, checks have little effect on the strength of glued laminated members. Checks usually appear on the wide faces of the lumber and do not materially affect the shear strength of the laminations. In cases where members are designed for loading parallel to the wide face of the laminations, checks may affect the shear strength of a beam. Their effect may be evaluated in the same manner as for sawn lumber.
Seasoning checks in bending members affect only the horizontal shear capacity. Regular checking due to seasoning has been considered in establishing allowable horizontal shear values. Checks are usually of structural importance only if they are significant in-depth, occur in the mid-height of the member near the supports, and the member’s design is governed by shear.
The size of the checks relates directly to the shrinkage stresses induced that are a function of several factors related to the properties of both the member and the environment. Proper initial moisture content specifications, shipping considerations, and job site storage procedures can significantly affect the moisture content of the wood.