A washing machine poses a double threat since water and heavy objects are both dangerous for wooden floors. That doesn't mean a washer can't be placed on a wooden floor, but there are some precautions to take that will prevent permanent damage from water and the constant vibration caused by both front- and top-loading models.
Uneven legs can cause the washing machine to vibrate and bounce when it is running, especially on a wooden floor that flexes more than a solid, concrete surface. This vibration can cause the washer to move around, leaving marks on the floor. Front-loading washers tend to vibrate more than top-loading models, but both can be helped by ensuring the legs are level on all four corners. Most models have self-leveling legs in back, and adjustments are made in the front. Keep the washer as low to the ground as possible to minimize vibrations.
Wooden flooring is usually nailed to the subsurface, which allows the boards to move slightly under the weight and action of the washing machine. The continuous movement loosens nails and, in turn, planks along the floor. Replace nails with screws to reinforce the floor and prevent the planks from becoming loose. Screws can withstand the vibration created by the washer without losing their grip on the planks and subfloor.
Hard plastic on the bottom of washer legs can scuff and ding wooden floors, especially during spin cycles when the washer is vibrating. Place soft, rubber cups on the bottom of the feet to stop the washer legs from scraping the floor. In addition, there are specialty cups that can be attached to both the legs and the floor to keep the machine in place.
A leak-proof floor tray provides a barrier between the washer and the floor in case of overflows, leaks and drips. The tray, usually made of heavy plastic, slides underneath the washer to catch water before it reaches the wooden floor and causes damage. In addition to protecting the floor directly underneath the washer, the tray prevents leaks from running across the entire room.
A leak sensor protects against major damage from a hose that may burst or problems at the valve, which can cause major damage as the amount of water isn't limited to what the washer can hold. There are two types of leak sensors -- one that warns of a leak or overflow, and one that includes an automatic shutoff that turns off the water in case of a problem.