That's an excellent and very practical question! The short answer is: it depends entirely on the type of finish on the bench. Some can become surprisingly slick when wet, while others are designed to maintain grip.
Let's break it down. Many traditional outdoor benches are coated with varnishes, polyurethanes, or lacquers. These create a hard, glossy shell that looks great when dry. However, when rain hits this smooth surface, it can form a thin film of water, significantly reducing friction. This is similar to how a tiled floor gets slippery. A bench with a high-gloss finish is often the most hazardous in wet conditions.
On the other hand, benches with oil-based finishes (like teak oil or linseed oil) or penetrating sealants tend to be much better. They soak into the wood rather than sitting on top, preserving more of the wood's natural texture. While they can still be wet, the surface generally offers more traction. Similarly, unfinished, naturally weather-resistant woods like teak or cedar have a rougher grain that provides inherent grip, even when damp.
The best options for slip resistance are benches specifically treated with non-slip additives in their coating or those made from textured materials like composite lumber or rough-cut stone. Regular maintenance is also key. Algae or mildew growth, common in shady, damp areas, can turn any surface into a slippery slide.
So, what can you do? First, identify your finish. A glossy, plastic-like coat is a warning sign. For added safety, consider applying a non-slip patio paint or a clear anti-slip coating designed for outdoor furniture. Placing the bench under a cover or in a sheltered area can also prevent it from getting dangerously wet. Ultimately, while a beautiful shine is appealing, prioritizing a finish with texture or a matte look will lead to safer, more reliable seating after a rain shower. Always exercise caution and dry off a bench before sitting, especially if you're unsure of the finish.