Simply put they're not meant to go there. I see highly upvoted DIY posts with glossy decks regularly enough that I finally had to make a post. So why shouldn't you do this?Regular interior glossy clear coats, like you use on your natural/stained/wood trim don't have the protective properties of exterior finishes. They're not meant for floors so they don't dry hard enough to prevent dents, scrapes, and resistance to foot traffic ultimately just rubbing off. Also, because they are interior protective coatings they don't have the UV inhibitors that an exterior purposed coating would have which will lead to whatever color underneath fading very quickly.Ok so I'll just use a clear meant for floors. Nope, if you notice all the cans of protective clears for floors say not for use outside. Now we are met with the opposite problem as before. Clears for floors dry to a much harder finish so they can handle all the abuse that floors take. That's fine indoors where temperatures remain constant. However, outside the temperatures swing wildly and whatever wood you have applied your coating to is going to expand and contract. Hard coatings do not like when the surface they are on expand and contract. Cracking, peeling, and bubbling are in your future. Again, because they are interior products they don't have UV inhibitors.Ok so I'll just use an exterior clear spar varnish/urethane/acrylic. It's meant for outside right? Yes it is. But not on walking surfaces. This takes us back to the problem in point 1. Exterior clears are super soft (relatively) so that they can expand and contract with the wood as temperatures change. If you put it on a floor it's going to dull down very quickly.IT IS AN EXTERIOR WALKING SURFACE. IF A SHINY WALKING SURFACE GETS WET PEOPLE ARE GOING TO BUST THEIR ASSES. That's why no major companies are going out of their way to try to formulate a product that manages to be hard enough to walk on but soft enough for the change in surface because it doesn't make sense to make a walking surface that is going to get rained on shiny. It's one reason why every exterior deck stain dries to a flat finish."But when I stained my deck the deck stain (transparent, semi-transparent, semi-solid) dried with a shine." That's because you over applied it. At most all you ever need is 2 very thin coats of exterior purposed deck stain. Usually one will do. Deck stains penetrate into the wood. If you apply too much the wood can no longer absorb any more stain and what you're left with is the stain pooling on top. When it pools on top you will be left with a very slight shine, mostly because it could never fully dry. You'll notice highs and lows of shine and dull because you've applied more in some spots than others.So that's it. Stop clear coating your decks.Source: Paint and stain are in my DNA. via /r/DIY https://ift.tt/2LZtjRA
