My Big Bang Theory

Not only is it tax time, it's gap time. We acclimate flooring to reduce seasonal gaps and help prevent abnormal gaps. But what happens when the flooring contractor does everything right and the structure is the problem?

I looked at a house this week with a gap problem. A big bang woke the homeowners up in the middle of the night. They discovered a piece of baseboard blown across the kitchen. They also discovered a big gap down the middle of their floor.

This house has a relatively open floor plan, with a kitchen in one corner. The flooring was respectably tight with normal minor seasonal gaps throughout, except for this one major gap of about 1/4" running end to end in the house. The location made me suspicious, and measurement revealed that the gap was about 16 feet from the front of the house, and 14 feet from the back. The front of the house was over a crawl space, while the back was over a basement, with 16-foot joists in front and 14-foot in back.

A little more investigation revealed that the joists butted together over a beam above the basement foundation wall. And since plywood comes in 4-foot-wide panels, the plywood subfloor joint fell right at the beam. Seasonal drying of the joists and subfloor caused them to shrink and pull apart at the beam. Granted, longitudinal shrinkage in a joist is about 0.1% from wet to oven dry, but that's almost 3/8" across this house. Plywood can shrink more, about 0.5" total over 4 feet on both sides of the joint.

So line up all the joints and you have something that can easily pull apart. Then dry things out in the winter, and the joint opens up. In this case, it did so in such a way that a piece of baseboard popped off and went sailing across the kitchen.

The builder decided to fix things, especially when I pointed out the building code section showing that these details weren't allowed. But it was ultimately a case of structural issues, not flooring issues.