a cracked limestone stair tread also showing a sunken patio stone
Q: The five steps leading to my house have 1½-inch-thick limestone treads. The bottom tread and riser have cracked. I'd like to replace this piece, but the only limestone I can get around here is 2 inches thick. Is there a way to solve this problem?
Fred Gauch, Warren, NJ

A: Tom Silva replies: I can imagine a couple of possibilities, though it would be a lot easier if you could get your hands on some 1½-inch-thick limestone. Have you checked architectural salvage lots? Craigslist? Online stone yards? This isn't just about getting the steps to match; it's also about safety. If the distance between the tops of the steps isn't exactly the same, you're going to trip on them every time.

I can see from the photo that one of the patio stones under the corner has sunk. That may be what caused the tread to crack in the first place. So, first, reset the stone, then remove the broken tread and repair the cracked riser.

If you're replacing it with a 2-inch-thick piece, you have to lower the riser by ½ inch. Use a hand sledge and stone chisel to knock out the old mortar, and, if necessary, some of the riser itself. This will be a little tricky, because you don't want to crack the riser or damage any visible surfaces. Be sure to wear safety glasses.

When you've chiseled off enough, set the new stone in a construction adhesive made for concrete block. It's much thinner than mortar and should work fine.
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