Replace Dangerous Rotting Deck Stairs

James Dulley
Wed, 24 Dec 2025 21:00:00 -0800
Lifestyle

Dear James: My old wood deck is deteriorating and the stairs could be hazardous. What is the easiest way to install new ones for an inexperienced DIY-er? — Shantell K.

Dear Shantell: You are correct to worry about walking on old, unstable stairs that don't have a handrail. It's easy to lose one's balance on them. We become accustomed to the standard height of a step. If the stairs are weak, sagging or on an angle, it can cause someone to stumble.

Building entirely new stairs, especially if some of the lumber already appears to be rotten, is a wise decision. The rotten areas are usually more extensive than they appear to be on the surface. Just take a crowbar and pry off the old stairs. Since they are made of pressure-treated lumber, don't burn them in your fireplace.
Updated: Thu Dec 25, 2025

Dear James: My old wood deck is deteriorating and the stairs could be hazardous. What is the easiest way to install new ones for an inexperienced DIY-er? — Shantell K.

Dear Shantell: You are correct to worry about walking on old, unstable stairs that don't have a handrail. It's easy to lose one's balance on them. We become accustomed to the standard height of a step. If the stairs are weak, sagging or on an angle, it can cause someone to stumble.

Building entirely new stairs, especially if some of the lumber already appears to be rotten, is a wise decision. The rotten areas are usually more extensive than they appear to be on the surface. Just take a crowbar and pry off the old stairs. Since they are made of pressure-treated lumber, don't burn them in your fireplace.

Most stairs for decks range between 3 and 6 feet wide. The easiest way to build the new stairs is using precut stringers which you can purchase at any home center store or lumberyard. Stringers are typically two-by-12's with notches cut in them to properly locate each step with the correct rise and run.

Unless your old stairs were an odd size, just get a stringer with the same number of steps as the old one. If your stairs are very narrow, you will need only one stringer on each side. For most stairs, though, you will need several stringers spaced no more than 30 inches apart to support the steps.

To make the stairs as stable and rigid as possible, pour a concrete footer at the location of the bottom of each stringer. The concrete needn't be very deep, so use two-by-sixes to make the form for the footers. Embed galvanized anchors in the concrete to attach the lower end of the stringers.

Use galvanized metal joist hangers to attach the top of the stringers to the skirt of the deck. These are special metal hangers made just for stair stringers. The bracket portion is tilted down at an angle to properly position the stringer.

Before you actually start nailing the stringers in the metal hangers, check all of the stringers for alignment. You can do this by laying a 4-foot level across the notches. You may have to adjust one or two of the stringers up or down for the proper alignment. Attach the bottom end of the stringers to the anchors in the concrete footers.

Always use galvanized or stainless steel nails for outdoor projects. They hold up much better than plain steel nails and will not create rust stains on the wood.

Using two-by-six lumber, cut the stair treads to length to allow for a 1-inch overhang at each end of the outside stringers. Use 12d or 16d spiral-shank casing nails to attach the treads.

Most stairs on decks are open stairs, meaning the vertical space between each step is open to beneath the deck. If you prefer to install vertical risers to block off the openings, it is much easier to install them before nailing the treads into place.