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Since living trees contain sap, newly sawn timbers are very high in moisture content. Moisture content within the timber varies greatly. In softwoods the sapwood contains more moisture than the heartwood, while in hardwoods the sapwood and the heartwood may have nearly the same moisture content. Because softwoods have a lower moisture content and are lighter than hardwoods they shrink less than hardwoods. Among the softwoods Douglas Fir will shrink more than Sitka Spruce and Pine.

Changes in timber dimensions, during drying, are not equal in all directions, in general:

  • Dimensional change is greatest in the girth of the timber.

  • Dimensional change in diameter is about half of that in the girth of the timber.

  • Dimensional change lengthwise is very small, about 2% of girth change.

The difference in girth and diameter shrinkage rates induces tension stress that often cause a lengthwise separation of the wood that extends across the rings of annual growth, which is called a heart check. Since a heart check only separates the wood cells they usually do not affect the structural capacity of the timber. Heart checks and shrinkage are primarily aesthetic problems. The only ways to eliminate heart checking is to either remove the heart of the tree from the timber or to kiln dry the timber.



The only trees large enough, in North America, to produce free-of-heart timber are trees such as the Douglas Fir, Sitka Spruce and Cedar that grow in British Columbia. We source all of our old growth wood from some of the finest specialty mills in British Columbia. We also have access to salvaged timber. When using salvaged timber the heart checks have already occurred, therefore, we can place the checks towards the outside of the building where they will not be seen.



The second method is to dry the timbers. Conventional drying takes anywhere from 6 to 8 weeks, but with new technology radio frequency/vacuum (RF/V) kiln drying, the drying time can be reduced down to several days. We have access to the largest RF/V kiln in North America. It can dry any size of timber up to 40 feet in length. When placing an order with a kiln we specify that the wood must be dried down to the same moisture content as that expected inside the heated building. Since Alberta's average moisture content level is one of the lowest in North America kiln drying is desirable to eliminate heart checking. Kiln drying is desirable for wood inside the heated interior of most North American buildings. When ordering old growth timber from British Columbia we often order free-of-heart RF/V dried timber.

Free-of-heart timber and the process of RF/V drying eliminate heart checking and significantly reduce checking and splits, but they do not completely eliminate small internal checks. There may still be small internal checks, but nothing the size of heart checks.

The majority of timber sawn in Alberta, and the rest of North America, is boxed heart cut and is not kiln dried. Since these timbers will heart check, they cost less than the old growth dried timber available in British Columbia. For these timbers we have developed a crack control method, similar to that used in the concrete industry. This method helps to drive the heart checks towards the outside of the building, where they will not be seen. Our crack control method helps to minimize heart checks but may not eliminate them. This work takes longer, but the extra effort ensures the highest quality timber frame possible.

We also have sources of seasoned reclaimed, standing dead and fire damaged timbers.

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