Putting plywood under granite countertops is a common practice in the installation process, but it is not always necessary. The need for plywood depends on the type of base cabinets you have, the weight of the granite, and the support requirements of the specific countertop installation.
Here are some factors to consider:
Cabinet Strength: If you have standard base cabinets made of solid wood or sturdy construction, they can typically support the weight of granite without the need for plywood. However, if your cabinets are older or made of weaker materials, adding plywood can provide extra support.
Granite Thickness and Overhang: Thicker granite slabs and larger overhangs (for breakfast bars or islands) exert more weight on the cabinets. In these cases, plywood may be recommended to help distribute the load and prevent potential sagging or damage to the cabinets.
Substrate Material: In some countertop installations, a layer of plywood or another suitable substrate may be required to provide a smooth and stable surface for the granite to sit on.
Support Structure: The support structure beneath the countertops, such as braces or brackets, can influence the need for plywood. A qualified installer will evaluate the situation and determine if plywood is necessary for proper support.
Building Codes and Guidelines: Local building codes or guidelines might specify requirements for countertop installations. It's essential to follow these regulations to ensure a safe and durable installation.
Ultimately, it's best to consult with a professional countertop installer or contractor who can assess your specific situation and provide expert advice on whether plywood is needed for your granite countertop installation. They can take into account factors like the size of the countertops, the type of cabinets you have, and any local building requirements to ensure a successful and secure installation.