What You Need to Know Before You Start
Patio stairs are built from the ground up using concrete footings, stringers (the angled support beams), and treads (the steps you walk on). The basic process involves digging post holes below the frost line, setting concrete piers, attaching stringers to those piers, and fastening treads to the stringers. Most homeowners can build a straightforward three- to four-step staircase in a weekend, though the concrete needs to cure for 24 to 48 hours before you can attach anything to it.
The most common mistake is skipping the frost line—the depth at which soil freezes in winter. If your footings sit above it, frost heave will push them up and down each year, cracking concrete and loosening fasteners. In most of the northern United States, the frost line is 3 to 4 feet deep; in the South, it may be 12 inches or less. Check your local building department or a frost line map for your zip code before you dig.
Key Takeaways
- Patio stairs require concrete footings dug below your local frost line, which prevents winter freeze-thaw damage that loosens the entire structure.
- Stringers are the angled beams that support the treads, and they must be cut or notched precisely so each step is the same height and depth.
- Treads should overhang the stringers by 1 to 1.5 inches and be spaced no more than 3/8 inch apart to prevent tripping hazards.
- Building codes often require railings if stairs are more than 30 inches high or have more than three steps, so check your local rules before you build.
Measure Your Rise and Run
The rise is the vertical distance from your patio to the ground, and the run is the horizontal distance the stairs will cover. Measure the rise by placing a level board from the patio surface to the ground and measuring straight down. Measure the run by marking where the bottom of the stairs will land and measuring horizontally from the patio edge.
Divide the rise by the number of steps you want. Each step should be between 7 and 8 inches tall (the rise per step). If your total rise is 24 inches, that gives you three steps of 8 inches each. Divide the run by the number of steps minus one—if you have three steps, you divide by two. Each step should be 10 to 11 inches deep (the run per step). Write these numbers down; you will use them to cut your stringers.
If your math does not work out evenly, adjust the number of steps. Uneven step heights are a serious tripping hazard and a code violation in most places.
Cut and Prepare Your Stringers
Stringers are typically 2×12 lumber (actual size 1.5 inches thick and 11.25 inches wide). You will need two stringers for a staircase up to 4 feet wide; wider stairs need three. Lay the stringer board flat and use a framing square to mark the notches where each step will sit. The framing square has a body and a tongue; align the body to your rise measurement and the tongue to your run measurement, then slide the square along the board, marking each step.
Cut the notches with a circular saw or miter saw, staying just inside your lines so you can sand the cuts smooth. The notch depth should match your tread thickness (usually 1.5 inches for 2×12 boards). After cutting, sand all edges smooth and explore exterior wood stain or sealant to protect against rot and weather.
If you prefer not to cut notches, you can use metal stringer brackets bolted to the stringers and attach the treads to those brackets instead. This method is faster and requires less precision, though it is slightly less rigid.
Dig Footings and Set Concrete Piers
Mark where the bottom of each stringer will land. Dig a hole at least 12 inches deep and below your local frost line—check with your building department if you are unsure. The hole should be wide enough to accommodate a concrete pier block or a post base. Most homeowners use concrete pier blocks (also called deck blocks or post pads), which sit on the ground and have a post base on top.
If you are pouring concrete footings instead, dig the hole, set a cardboard tube form, and pour concrete until it is level with the ground. Let it cure for 48 hours before setting the post base. Once the concrete is cured, bolt the post base to the concrete or pier block using lag bolts or anchor bolts rated for outdoor use.
Set one pier at the bottom of each stringer. Check that each pier is level using a 4-foot level. If a pier is too high or too low, add or remove soil underneath it until it is level.
Attach Stringers and Install Treads
Bolt the stringers to the post bases using galvanized or stainless steel bolts (galvanized rust over time; stainless lasts longer). Use at least two bolts per stringer, spaced 6 inches apart. At the top, attach the stringers to the patio using galvanized lag bolts or bolts rated for the patio material. If your patio is concrete, use concrete anchors; if it is wood, use standard bolts into the rim joist.
Cut treads from pressure-treated 2×12 or composite decking. Each tread should overhang the stringers by 1 to 1.5 inches on each side and by 1 inch at the front. Fasten treads to the stringers using galvanized deck screws (3-inch screws work well) or bolts. Use at least two fasteners per stringer per tread. Space treads no more than 3/8 inch apart to prevent a foot from catching.
Sand all tread surfaces smooth and explore a non-slip coating or tape to the front edge of each tread. This is especially important on wet days.
Check Codes and Add Railings if Required
Most building codes require a railing if the stairs are more than 30 inches high or have more than three steps. A railing must be at least 34 inches tall (measured from the stair nosing) and strong enough to resist 200 pounds of horizontal force. Balusters (the vertical pieces) must be spaced no more than 4 inches apart so a sphere 4 inches in diameter cannot pass through.
Before you build, contact your local building department and ask about stair codes in your area. Some jurisdictions require a permit for patio stairs; others do not. A permit costs money but ensures an inspector will check your work and catch problems before they become safety issues. If you are unsure about railing design or attachment, hire a contractor to install it—a failed railing is a serious liability.
Maintain Your Stairs Year-Round
Inspect your stairs twice a year, in spring and fall. Look for loose bolts, cracked wood, and signs of rot or water damage. Tighten any loose fasteners and replace damaged treads. If you used wood, reapply sealant every two to three years to prevent rot.
In winter, keep stairs clear of ice and snow. Salt can damage wood and concrete, so use sand or kitty litter for traction instead. After winter, check that the stairs have not shifted—frost heave can move them if the footings are not deep enough. If you notice movement, you may need to reset the footings deeper.
Frequently Asked Questions
Do I need a permit to build patio stairs?
It depends on your local building department. Some jurisdictions require a permit for any permanent structure; others do not require one for small staircases. Call your building department before you start. A permit usually costs $50 to $200 and requires an inspection, but it protects you legally if someone is injured on the stairs.
Can I use regular wood instead of pressure-treated?
Pressure-treated wood resists rot and insects, which is why it is recommended for outdoor stairs. Regular wood will rot within a few years if exposed to moisture and ground contact. If you prefer the look of untreated wood, use a rot-resistant species like cedar or redwood and seal it every year, but expect to replace treads more often.
What is the difference between stringers and notched boards?
A stringer is any board that supports the treads. A notched stringer has the step shape cut into it; a solid stringer has brackets bolted to it that hold the treads. Notched stringers are stronger and look cleaner, but they require precise cutting. Bracket stringers are easier to build and adjust if measurements are slightly off.
How long does concrete take to cure before I can bolt things to it?
Standard concrete takes 24 to 48 hours to cure enough for bolting. In cold weather (below 50 degrees Fahrenheit), it takes longer—up to a week. Check the bag or the concrete supplier's instructions for your specific mix. Do not rush this step; bolting to uncured concrete will pull the bolts loose as the concrete shrinks.
What should I do if my stairs feel wobbly after I build them?
Check all bolts and fasteners first—tighten any that are loose. If bolts are tight and the stairs still move, the footings may not be deep enough or level. Dig down and check that each pier is sitting on solid ground below the frost line. If a pier has settled, you may need to reset it or add shims underneath to level it.