Yes you can pressure wash your decking however there is almost an “art” to do it correctly without damaging the wood. Using too much pressure, the incorrect nozzle tip or being too close to the wood will fur up the wood, split the edges and cause “tram lines” in the surface. To properly clean decking the correct pressure and nozzles must be used followed my chemical treatments to soak into the wood to kill the green growth that is deep in the wood. Unfortunately these chemicals are once again controlled substances and restricted and sold only to professional service providers.