Cracks down middle of wide pine planks

Q: I recently built a house in the Northeast and installed 11 inch wide T&G pine floors. Since then many of the boards have cracked along the board. I am not talking about gaps between boards, although we have many of those some even bigger than 1/4 in. Many of the cracks seem to be more closer to the edges than down the middle, although again a few have cracked down the middle. My contractor says this is normal with such wide boards but I can’t imagine that that is so.

The boards were installed in the winter and were face nailed in the summer with no AC on in the house until long after the boards had been laid. Please give me some advice as to what you think the cause is and if this is to be expected.

A: You have to be very careful with pine. I have seen quite a few, much narrower boards that experienced severe shrinkage, leaving large gaps between boards after installation. The wider the board, the more likely is the possibility for severe expansion and contraction. The flooring has to be down about 9% moisture content, and be within 4% of the sub floor. It seems apparent that these boards have shrunk a lot. Since it was face nailed, the board has pulled on the nail and cracked in places.