Consistent heating and cooling can cause cracks in wood shingles. The expansion and contraction process affects water that may have entered spaces in the shingles. When heated, the water expands potentially causing small cracks. Over time, the cracks increase in size and may split the shingle into several pieces. As the weather changes and the shingles cool, the contraction may loosen the attachment to your roof. When shingles are loose or cracked, they can expose your roof's structure to moisture and possible decay. To prevent moisture damage from cracked shingles, try filling them with roofing cement. Installation can also cause cracks in wood shingles. Nails used to secure the roof may crack or split the shingle. Proper installation can help prevent future problems with shingle cracking. Contact a roofing specialist for more information on wooden shingle cracking.