The most common chemical used in professional deck cleaning products is sodium hydroxide, and it has proved to be the most effective.
Preparation
Gather all the equipment that you are likely to need: a ladder, garden hose, leaf blower or broom, protective gear like gloves or overalls to keep you protected from the chemicals you will be using, and the deck-cleaning solution.
Remove everything from your deck--flowerpots, barbecue grills and deckchairs. Clear away large debris and dirt with a broom or by hand. Repair any visible structural damage to your deck, such as loose boards, loose screws and bad wood. Cover all electrical outlets to prevent electrocution.
Cleaning
Sodium hydroxide is the chemical most commonly used in deck cleaning solutions because it doesn’t need to be sprayed at high pressures to be effective. This is because the chemical itself does most of the cleaning. One good clean with this chemical is better than multiple sub-par ones.
After you’ve cleaned your deck, it’s likely that your wooden slats will turn black. This can be rectified by neutralizing the whole deck with a weak acid like citric or oxalic acid, which will turn it back to its original shade. You should always neutralize your deck after cleaning with sodium hydroxide even if there’s no discolorization. This is because the caustic base causes the wood to degrade and rot faster than it would otherwise. After you finish cleaning, reseal it with a good sealant to prolong its longevity.