What Should you Spray on a Wooden Park Bench to Protect it From Rain?

How Sealants Work

• A waterproofing sealant soaks into the wood, as water might do, and enables it to repel water. Most have some sort of varnish in it, as well as a variety of chemicals that treat the wood and build a barrier that keeps water out. Some varieties also have mild fungicides that prevent wood from mildewing and decaying. On their own, these treatments don't change the color of the wood, so unfinished or unstained wood will likely turn gray over time.

Aerosol Sealers

• There are a few kinds of sealant products that can be applied by aerosol can. These spray on in minutes and soak into the wood, protecting it from rain. The spray goes on clear, and may at most make the wood look damp. Don't expect it to drip off; if it does, you may be applying the spray too liberally. These cans are small, but one should cover all of the wood on a bench fairly easily. Most hardware stores have a handful available, and they are usually near the spray paints. Thompson is one of the most well-known brands, but there are others you can use.

Sealers in a Paint Sprayer

• If you have paint spraying equipment available to you, there are a few sealants that can be applied this way. Paint sprayers usually take paints that could be applied by brush and spray them on instead, and the same can be done with waterproofers--although, be sure to read the can before doing so. These are sometimes mixed with stains or paints, and so you can do twice the work with one can: coloring and sealing the wood. You will also want to consider other factors, such as the base and lifespan of the product. Oil-based sealants will trap moisture in, while water-based will let it evaporate. The life of a product is affected by its opacity and percentage of solids--the higher opacity and quality of the product, the less often you will have to reapply it to your bench.

Reapplying

• Over time, the sealant will lose its efficacy and you will need to reapply it. Generally, the service life of these products is about a year, especially if the bench is exposed to the elements year-round. A treatment at the beginning of spring will keep the wood in great shape for the rest of the year to come.

  You can test the sealant by dripping a small drop of water onto a level seat slat, and watching how the wood responds: If it beads on top and doesn't soak in, the sealant is still working; if it soaks into the wood, then you definitely need to reapply it.