When you pressure wash a wooden deck, you really do so with two goals in mind. Primarily, you are seeking to remove algae and other contaminants from the deck, leaving it clean. But you're also aiming to do this without causing any damage to the deck. It is important to weigh both of these goals as you go about pressure washing your deck. Follow these tips for the best results.
1. Use a detergent.
Yes, you probably could get the deck clean with the pressure of the water alone. However, you have to turn the pressure up higher and spend more time spraying when you do not use a detergent. Use a cleaner made specifically for wood, and follow the instructions on the bottle. Typically, you are told to apply the detergent at a low pressure, let it sit and work for about 10 minutes, and then pressure wash it away on a higher pressure setting. Resist the urge to cut the "rest time" short, as this will only make it necessary to apply more pressure when you wash.
2. Use the lowest effective pressure.
Some pressure washers change pressure as you change the spray tip. Others change pressure via a dial. Regardless of how yours works, you should always try cleaning your deck with a lower pressure setting, and then turn it up slowly just until you feel the needed effectiveness is achieved. This way, you will reduce the risk of blasting away chunks of wood as you wash.
3. Spray with the grain of the wood.
You will get a cleaner deck and you will also loosen fewer wood chunks if you move the pressure washer wand with the direction of the wood grain rather than spraying back and forth across the grain. Start at one end of the board, and work your way towards the other end.
4. Choose a dry day.
It's important to spray your deck on a day when it will dry quickly, as this will reduce the amount of moisture damage the wood will suffer overall. Do not power wash your deck when it is going to be rainy and wet outside for days afterward.
With the tips above, you can satisfy both goals of power washing: cleaning and minimizing damage. You'll be doing your best to use the equipment as it is intended, and you'll also be using detergent to make the task easier.