I'd caution against power washing if there is any kind of supporting timber structure underneath. Attached are some pictures of the joists of a deck I had to rebuild for a client who had taken to regularly jet washing their deck. The decking material is usually much harder than the subframe which is just made from regular construction lumber so much more able to absorb damage from the jetwash. This means that you can be causing damage that you won't see. In the case of my client he was aware that the deck was becoming bouncy but didn't realise the extent of the damage until he fell through it and wound up in a plaster cast.
I'd caution against power washing if there is any kind of supporting timber structure underneath. Attached are some pictures of the joists of a deck I had to rebuild for a client who had taken to regularly jet washing their deck. The decking material is usually much harder than the subframe which is just made from regular construction lumber so much more able to absorb damage from the jetwash. This means that you can be causing damage that you won't see. In the case of my client he was aware that the deck was becoming bouncy but didn't realise the extent of the damage until he fell through it and wound up in a plaster cast.