Our 3/8" Textured Virgin Rubber Tiles can be installed on top of a wood porch. These tiles are non-porous and will not allow water to pass through them. Water would be able to flow through the cracks around the interlocks if they are not interlocked tightly. Since these tiles are made from rubber, they are weather-resistant and mold and mildew resistant. The only issue you made run into with these tiles is that they fade in direct sunlight due to them not being UV stable.