A split seat on a wooden chair often sends it to the junk heap, but this solution may save one at your house. The fix begins by forcing wood glue into the crack and clamping the seat back together. While this will put the chair back together, it may happen again.
To prevent it from happening again, add a pair of 1″x 4″ cleats to the underside of the seat to support the repair and the entire seat to prevent future cracks. We made our wood cleats from oak, beveled the edges and stained them to match the chair. Be sure to attach the cleat with screws that are long enough to hold it in the chair seat, but not so long that they come through the top of the seat.