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How to Build a Deck: Composite Stairs and Stair Railings

Marc McCollough

By Marc McCollough
Updated April 23, 2021

With composite decking and deck railings installed, complete the look with composite stairs. Building deck stairs for composite decks is slightly different than building wood stairs. Here's how to build a set of composite steps.

Skill

Advanced

Time

One Weekend

Tools and Materials

Tools

Materials

Note

Product costs, availability and item numbers may vary online or by market.

Deck Stair Basics

Illustration of Composite Deck Stairs.

This deck already has composite decking and deck railings installed. See the steps in How to Build a Deck: Composite Decking and Railings. It's common to build the framing with treated lumber and use composite surface material, as with the decking and stairs on this deck.

Composite deck stairs are typically made from 2 x 12 pressure-treated stringers spaced about 8 to 16 inches apart. They rest on a solid foundation and are attached to the deck with hangers. They have risers (also called toe kicks), treads and railings. Stairs should be at least 36 inches wide.

You can build your own custom stringers or get pre-cut ones at Lowe's. Custom-built stringers allow you to match the dimensions of a set of stairs in your home, which will feel most comfortable. Whichever you choose, always make sure you follow building codes.

Good to Know

Some codes require toe kicks.

Stair Measurements

Illustration of Determining the Location of the Stairs.

Determine the location of your bottom step. Set a long level or straight 2 x 4 on top of the decking, and measure the height at the point where you want your steps to end. Use this measurement to determine the number and height of the risers.

For example, if the height is 55 inches, divide this measurement by 7, the ideal height in inches for each step. Round to the nearest whole number to get the number of risers — in this case 8. Now divide 55 by 8 to get the actual height of the risers — in this case it's 6-7/8 inches.

55 ÷ 7 = 7.86 rounded up to 8 risers

55 ÷ 8 = 6.875 or 6-7/8 inches

If you use the deck itself as the top riser as with this deck, subtract one step.

The stair treads will be made of composite decking planks — two for each step — making the run for each step (the distance front-to-back) about 11 inches. There are risers or toe kicks on the back, made of pressure-treated wood and composite boards without grooves.

Good to Know

You may want to check the height of steps or stairs that are already familiar to you, such as interior stairs or porch steps, to get a sense for a comfortable height. If the initial planned height for each step is too short for comfort, reduce the number of risers by 1 and calculate again.

Good to Know

You’ll often see decking boards listed with a common (or nominal) measurement of 5/4 inch thick. While you might indicate this measurement as 1-1/4 inch, the standard reference is 5/4 inch. Also note that the actual measurement of the thickness of a 5/4-inch board is usually 1 inch. See our video Why Is a 2 x 4 Not 2 by 4? to learn about the difference between common/nominal measurements and actual measurements.

Creating a Stair Landing

A concrete pad is one common type of landing. It has a 4-inch layer of gravel underneath and extends beyond the steps about 36 inches. You can find step-by-step instructions for pouring a concrete pad landing in How to Build a Deck: Wood Stairs and Stair Railings.

This deck uses another option — concrete footers like those that support the deck frame. You'll need to determine the correct location for the footers.

Good to Know

Our Concrete Holes and Pillars Calculator helps you estimate how many bags of concrete mix you need to set your posts.

Instructions

Cutting the Stringers

When you have the rise and run determined and the footers installed, mark the stairs on 2 x 12s to create stringers.

Instructions

Attaching the Stringers, Toe Kicks and Treads

You'll attach posts to the footings you poured above and run the stringers between the deck and the posts. Once the stringers are secure, you can add the toe kicks and treads.

Instructions

Installing the Stair Railings

The stair railings include vinyl top and bottom rails, as well as balusters.

Instructions

Working with Pressure-Treated Lumber

Guidelines

  • Use fasteners and hardware labeled for treated lumber — stainless-steel or hot-dipped, galvanized screws.
  • If the lumber is wet — it typically is when delivered from the store — butt it together tightly when building. Pressure-treated wood shrinks as it dries.
  • Drill pilot holes in the ends of boards to prevent splitting when you nail or screw them together.
  • Use wood rated for ground contact when necessary for the project.

 

Safety

  • Wear a dust mask and eye protection when handling or cutting wood.
  • Wash your hands after working with treated wood.
  • Dispose of sawdust and waste according to local regulations.
  • Don't burn pressure-treated wood.
  • Don't use pressure-treated wood as mulch.

Read more about pressure-treated lumber and wood preservatives on the EPA website:

Overview of Wood Preservative Chemicals.

Finishing Touches

With the deck complete, make it stand out with the right furnishings and accessories. See how in How to Build a Deck: Finishing Touches.

Watch the complete deck series at Lowes.com/BuildaDeck.