Here in the pacific northwest our wooden stairs do...

Here in the pacific northwest our wooden stairs don't just get wet they stay wet. When that happens algae grows on them (happens to composite roofs too) and makes them as slick as if you had smeared grease on them. The HandiRamp 48" aluminum non slip treads have been the ONLY solution that has worked for more than one season. They work great mounted about 3/4 of an inch from the edge of the step. In that position you shoe will always get a grip. I've had a set (brown aluminum) on our back porch stairs for about 4 years now and the still look good and work great.