Hello, I am a representative of Trex. To stop the squirrels from chewing on the deck, you can use an animal deterrent as long as it is not a petroleum-based product. Make sure that any food left on the deck is cleaned and if you have used a sodium hypochlorite product to wash the deck, it is thoroughly rinsed off.
Hosing off may be all that is needed to remove lose dirt and debris. For basic cleaning use soap, hot water, and a soft bristle brush. We suggest a semi-annual cleaning of your Trex deck, typically in the spring and fall. You can access our care and cleaning guide with other recommendations by following this link: http://www.trex.com/own/care/index.htm