How to Build Rock-Solid Deck Stairs With Concrete

There’s a lot to be said for uncut stringers. For one thing, they are stronger than cut stringers and make it possible to build stairs with longer spans without intermediate supports. And if the tread material is strong enough, a 3- to 4-foot-wide stair will require only two stringers. That’s not possible with composite tread stock, of course, and, even with 2x12 treads, the stairs would be limited in width to 36 inches. But by using concrete treads and 4x12 solid stringers, we can build exterior stairs as wide as 48 inches that are strong, visually appealing, long lasting, and less expensive than cut-stringer stairs.

At first glance, front porch stairs may look a little unconventional with uncut stringers and concrete treads, but we’ve been building them this way for more than 20 years and have found that not only have the ones that we’ve built performed well over this time, but they also look like they will last decades more with minimal maintenance.

Concrete Treads

We source stock precast concrete treads from Puget Sound Precast (psprecast.com). They’re made with 4,000‑psi concrete reinforced with a grid of #2, #3, or #4 rebar (depending on the size of the tread) and have four threaded inserts—two at each end—embedded in the bottom for 3/8-inch-diameter bolts. A pair of galvanized L-brackets, which bolt to the inserts and the stringers, are included with each tread to support it.

On this project, we used stock treads with an exposed aggregate finish (a broom finish and custom finishes and colors are also available). The 42-by-12-by-2 1/2-inch treads weigh 105 pounds each; other stock sizes range from 36 to 48 inches in length. The treads we bought cost about $58 each, which included the galvanized brackets, lag screws for fastening the brackets to the stringers, and machine bolts for fastening the treads to the brackets.

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