Great question. I am a believer in power washing. If your deck has not been stained in about 2 years, power washing will get the dirt out like you won’t believe. There are some that do not recommend power washing a deck, but I believe power washing will do a better job than the cleaners, with less effort. However, it does take some practice to use a power washer. You don’t want to use a spray nozzle with a tip that is less than 20 degrees spray. If you do, it can scratch the wood and leave marks. Use a wide spray, and after practice, you will get the feel. Sometimes, you will need to have the nozzle closer than 12” to the wood, but as long as you are using a wide tip or spray, you shouldn’t have any trouble. If you are planning on doing the work yourself, a power washer can be a good investment. Just be sure to allow enough time to do the job correctly.
If your deck has mold on it, you may need to use a bleach solution. Simply spray it on, let it sit for a few minutes, then power wash it off. However, if you are power washing the vinyl siding of your home, and it has mold (usually on the North sides), do not let the bleach sit longer than 2 or 3 minutes. If you do, it could discolor the siding.
The electric power washers are good, although generally not as powerful. They are also much lighter if you should have to carry it. I believe that you don’t have to buy the most expensive power washer, so do some research to see what is best for you.
After power washing your deck, be sure to let the deck dry for at least two days before applying a stain or sealer, and be sure to follow the directions of the stain manufacturer for the amount of time that is required afterwards where there won’t be any rain.
When power washing your home, a ladder may be needed. If so, remember that the ladder will be wet, so use a great deal of caution.