Anyone that has a sap-producing tree lingering over a deck can tell you that stuff isn’t easy to get off. If you find yourself in that situation, here are some ways to get that sap off your deck according to wisegeek.com:
Applying stain remover
There are a few things that do a pretty good job at removing sap from your deck. One of the best is stain remover. A few others to consider are an exterior deck stripper or oil soap. To apply the stain remover or the oil soap you can use a mop. If you plan on using the exterior deck stripper, a brush can be used.
Let it sit
With any of these solutions, they need time to sit on the sap before being removed. Let them all sit for approximately 15 minutes. After that time has passed, you should be able to scrub the sap off with a brush. Before rinsing off any of your solutions, make sure that it will not harm the environment. If it does, be very careful with your clean-up.
wisegeek.com