Oh, subway tiles-total classics, right? I've used 'em in kitchens, bathrooms, even a laundry room once. But here's the thing: people think all subway tiles need the same trowel, and that's where they mess up. Let me break it down for you, 'cause size does matter here.
First, let's talk about the standard subway tile: the 3x6-inch ones. These are usually thin-like 1/4-inch thick max. For these, a 1/4-inch V-notch trowel is your best bet. Why V-notch? 'Cause those little V-shaped notches hold just enough mortar to stick the tile without oozing out between the grout lines. I did a kitchen backsplash with 3x6 subway tiles last month, used a 1/4-inch V-notch, and it was smooth sailing-no scraping excess goop off the tiles, no messy cleanup. Trust me, I tried a square notch once for these, and I spent an hour wiping mortar out of the grout lines. Never again.
Now, if you're using bigger subway tiles-like the 4x8 or 6x12 ones-you gotta adjust. These are still thin, but they're larger, so they need a little more mortar to stay flat. A 1/4x3/8-inch square notch trowel works here. The "3/8" part gives just enough extra mortar to cover the bigger surface area, but not so much that it makes a mess. I laid 6x12 subway tiles in a shower last year, used this size, and the tiles sat perfectly level-no wobbles, no gaps.
And one quick tip: if your subway tiles are glass (super popular now!), stick with the V-notch too. Glass tiles are delicate, and too much mortar can make 'em crack or look cloudy. I had a client once who used a 3/8-inch square notch on glass subway tiles-half of 'em cracked when he pressed 'em down. Had to tear 'em out and start over. Save yourself the hassle: 1/4-inch V-notch for standard 3x6, 1/4x3/8-inch square for bigger ones.
