Can I install solid surface countertops over plywood or do I need to remove it?
I’m assuming you mean plastic solid surface like Corian, Fountainhead, Jetta or similar products. These can be installed over plywood, but they need air circulation on both sides for dimensional stability. Failure to provide that could result in warping or cracks in joints or stress areas. You can provide circulation by using a furring strip 1-1/2″ wide as a border and interim spaced support framework to lift the new counter above the plywood, and then cutting holes through the plywood in the openings. The strip could be as little as 1/4 or 3/8″ thick. The holes need to be perhaps 10-20% of the area of each pocket in the furring. The holes would then be above the drawer/cabinet storage and allow air movement need to accomplish a stable environment. One of the main reasons this is not done is thickness; you wind up raising the counter. Be sure that doesn’t create conflicts with your sink or other items- such as your microwave not fitting under the upper cabinets.
