Engineering and Construction

Where the edges of ß oors and roofs of a heavy timber frame are supported on concrete or masonry, special attention must be given to the potential for differential shrinkage between  the outer walls and the interior wood  column supports. Wood, compared  to masonry or concrete, expands  and contracts more with changes in  moisture content, particularly in the  direction perpendicular to its grain.

These changes occur over a period of  years as large timbers gradually dry  and seasonally with changes in ambient conditions. A heavy timber frame  building is detailed to minimize the  effects of this differential shrinkage  by eliminating cross-grain wood from  the interior lines of support. In traditional Mill construction, cast iron

Figure 4.7 Minimum sizes for solid wood members used in Type IV Heavy Timber construction, as specifi ed in the IBC.