How to Attach Stairs to a Deck: Methods, Steps, and Mistakes to Avoid

A deck can be an extension of your home’s living space, but it also comes with various safety hazards. One such hazard is deck stairs that are not correctly attached to the main structure and landing pad, causing the stairs to become unstable and potentially leading to injury. This guide explains how to attach stairs to your deck, ensuring your outdoor space is safe and secure.

Why Do I Have to Attach Stairs to My Deck?

Stairs have several parts, including stringers (the boards along the staircase sides), treads (the horizontal steps that you walk on), and risers (the vertical boards that form the back of each step). 

For safety purposes, the stringers must be attached to both the deck and the landing. If the stringers are not attached properly, they can come loose from the deck while someone is walking up or down them, potentially causing them to fall and injure themselves.

How Much Does It Cost to Attach Stairs to a Deck?

The exact cost to attach stairs to a deck depends on the installation method and the size of the staircase. You can expect to pay more if you’re constructing the staircase from scratch. The cost to build a deck ranges from $4,350 to $12,560, and this price may include stair installation if you complete everything at once. In general, expect to pay between $25 and $50 per stair to build deck stairs.

How to Attach Stairs to a Deck

Once you’ve built your deck stairs, it’s time to secure them to the deck and landing. Here’s how to do it.

Choose an Installation Method

There are three methods for attaching stairs to a deck.

• Attach the stringers to the rim using lag bolts. This method will extend the deck surface over the stringers, which may not be suitable if you have limited space.

• Secure the stringers to the posts using a ledger and an adjustable slope hanger. This method reduces the additional load on the deck frame and is usually the best option when attaching a long staircase. 

• Bolt stringers to deck joists using carriage bolts. This method is often the simplest and works well to secure the stairs to the deck thoroughly.

Once you have decided on the best installation method for your project, gather your supplies and proceed to the next step.

Test-Fit the Stringers

Before attaching the stairs to the deck, test-fit the stringers to ensure they are in the correct position. Don’t use force; if you have to jam the stringers into place, you may damage them. 

Adjust the Stringers

After test-fitting the stringers, use temporary screws to hold them in place while you check the placement. Use a level to check that the stringers are installed correctly and evenly. Level stringers mean that your stairs won’t be uneven, with one side higher than the other. Make adjustments as needed until the stringers are even within 1/16 inch.

Secure the Stringers to the Deck

Once the stringers are in the correct place, it’s time to secure them to the deck. Depending on your chosen method, you’ll need lag bolts, slope hangers, or carriage bolts. 

To attach the stringers to the rim using lag bolts:

• Screw in the bolts from the inside of the deck rim. 

• Use two bolts—one toward the top of the rim and one toward the bottom—to ensure the installation is secure.

To attach the stringers with slope hangers:

• Secure the hangers to the deck using nails and screws.

• Screw the hanger to the stringer’s inside face. 

• Repeat until all the stringers have been attached to the deck.

To bolt the stringers to the deck joists:

• Position the screws low on the stringers for maximum strength. 

• Use three carriage bolts per stringer: one at the top, one at the bottom, and one just in front of the bottom bolt to create a triangular shape. 

Secure the Stringers to the Landing

Once the stringers are attached to the deck, secure them to the landing to prevent movement. There are three ways to do this: 

• With galvanized brackets to secure the stringer and the concrete. 

• With a pressure-treated kicker board secured with masonry bolts.

• Embedded in concrete and secured with brackets.

The landing pad must be secure; many people opt to pour a concrete pad for this purpose. However, you can also use pavers or gravel as a landing pad.

How to Avoid Improper Deck Stair Installation

If your stairs aren’t correctly attached to the deck, they will be wobbly and dangerous to walk on. That’s why it’s essential to attach your deck stairs correctly. Follow these tips to avoid potential problems down the road.

• Measure carefully to ensure the stairs are level once attached to the deck.

• Choose the right attachment method for your deck stairs.

• Always secure fasteners near the stringer’s bottom edge for maximum strength.

• Don’t forget to attach the stairs to the landing pad for a secure fit.

DIY vs. Hiring a Pro

Attaching stairs to a deck is an advanced DIY project that is not suitable for many homeowners. If you make a mistake during this job, you could risk compromising the safety of any family or friends who use the stairs. However, that doesn’t mean you can’t complete this job yourself; just be diligent in following each step carefully and checking the fit and slope along the way to ensure the stairs are safe to use once installed.

If you’d prefer to leave this project to a professional, a local deck builder can help. Professional deck builders are experienced in attaching stairs to decks correctly to ensure they’re safe to use and won’t budge.