Hardwoods such as mahogany are very dense making them exceptionally durable, but they also do not absorb stains and sealers as well as softwoods. This requires more frequent sealing and cleaning. The deck should be cleaned before every application of sealant to ensure proper bonding. This should be done every year, preferably in the spring so you can enjoy your deck's new finish in the summer.
Regular pressure washing of your mahogany deck, especially before applying a sealer, will keep your deck looking good all year. Power washing with a proper detergent for wood decking will not only remove dirt and grime but will also restore the proper pH level to help the wood bond to the sealer or stain. Power washing a deck saves time and work if done carefully and with low pressure. The high flow rate from the power washer makes rinsing quick and easy, and the soap injector system applies the wood cleaner evenly and effectively.
Use a wide angled tip kept at a safe distance. Low pressure will work fine if coupled with a good detergent. Never use a turbo tip or tip of less than 25 degrees on your deck. Remove furniture and plants from the deck and apply the detergent according to the manufacturer's recommendations. Let the cleaner sit on the deck for several minutes before rinsing, but never let it dry. On large decks, work in sections to keep the surface wet at all times. Rinse the deck thoroughly using even overlapping passes, and wait until dry before replacing the furniture. Wait 48 hours before sealing or staining the mahogany.
Power washing can be harmful to your mahogany deck if not done properly. Power washers are capable of shredding the upper layer of the deck, raising the grain and even gouging the surface. Practice using your power washer on a scrap piece of wood or inconspicuous area first, and wait until the wood is dry to gauge the results. Keep the tip at a safe distance from the decking; too close and damage can occur. Never use hot water on mahogany decking, and never use a chlorine bleach or harsh detergent. Use only oxygen bleaches and mild detergents meant for use on wood surfaces.