I was talking with someone today who had a garage with almost no slope and needed to lay something down to keep the liquids and debris off his already bad concrete garage floor. The road salt is really hurting and breaking down the cement, and hes trying to keep the liquids from leaking through down to a storage garage below, something waterproof or water tight. The Garage Floor Mat G-Floor is about the only garage floor mat that can really say it holds the water back, and being made of tough vinyl it will stand up to all the salt, dirt/mud and other nasty stuff. We talked about washing the mat, and since he dose not have a slope, I recommended the standard thickness. This is a bit lighter weight and will be that much easier for him to drag out of the garage in the spring and wash it off with mild soap and water. I recommend the ribbed top because he will lay two mats together and over lap them or lay them up next to each other. The ribbed top will channel the water / liquids and keep them from traveling sideways to where the mats meet up. You can use 2x4's on the edges, under the matting in order to channel the water or liquids back to the center of the mat where it will evaporate and or dry up.
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This garage floor mat G-Floor comes with different top patterns - Diamond, Coin, Levant (leather look), and Ribbed. You can see all these at Mymatting.com, great prices and great service too!