I've been curious about the differences in sanding grits for outdoor decks versus indoor flooring. Why is it recommended to use sandpaper with a grit of 120 or lower on decks, while it seems to be okay to use 220 grit on flooring before staining? Thanks for your help with this!
3 Answers
From my experience, I’d say it comes down to how the wood is treated and how finishes bond. Decks are often made of softer woods that can absorb water, while indoor floors are generally hardwoods. Using higher grit sandpaper can leave the surface too smooth, making it difficult for finishes to penetrate properly. I usually stick to about 120 for decks, as Osmo suggests. For interiors, I sand up to 180 and then use 220 between coats.
Great question! The main reason is that decks are usually outside and exposed to the elements, meaning they're going to wear out faster than indoor floors. 220 grit might be too fine for a deck since it won't hold up as well against rain and sun. Meanwhile, indoors, people walk barefoot on floors, and that smoother finish is more desirable. It helps keep the surface nice and comfy. So, a finer grit is actually beneficial for interior flooring, but not for outdoor decks.
There are a couple of key points here: finer sandpaper produces finer sawdust, which can clog the pores of the wood, making it harder for finishes to adhere correctly. Also, different finishes require different surface textures to bond well. Higher grit works better for finishes that need to settle into smaller grooves, which is why it's recommended for flooring. Generally, I follow the manufacturer's specs closely because they’ve done the R&D on this.
Exactly, and it's all about the finish too! Softwoods and the wear they get outdoors really change the requirements for sanding grit.