With the composite decking and the deck railings installed, complete the look with composite stairs. Building deck stairs for composite decks is similar to building wood stairs, with a just few slight differences. Here's how to build a set of composite steps.
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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.
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.
Some codes require toe kicks.
You may want to check the height of steps or stairs that are already familiar to you — such as interior stairs of porch steps — to get a sense for a comfortable height. If the initial planned height of your steps is too short for comfort, reduce the number of risers by 1 and calculate again.
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.
Our Concrete Holes and Pillars Calculator helps you estimate how many bags of concrete mix you need to set your posts.
Calculate the total length of the run by adding together the runs for each individual step.
Mark the deck where the steps will attach.
Install the footers and posts in line with the two outer marks, at the total distance of the run. You can make the footers even with the ground. Look at Build a Deck: Post Holes and Framing to get step-by-step instructions for creating footers and setting posts.
When you have the rise and run determined and the footers installed, mark the stairs on 2 x 12s to create stringers.
Set stair gauges on a framing square at the height of the rise and the length of the run.
Hold the square at the corner of the 2 x 12 plank and mark the top run.
Slide the square along the plank and mark both rise and run for the next step. Continue marking until you have the correct number of steps laid out.
At the run mark you made for the top step, subtract the thickness of the toe kick — treated board and composite board — and strike a perpendicular cut line. This line indicates where the stairs attach to the deck. There won't be a toe kick at this point of the stairs.
At the bottom step, subtract the thickness of a tread from the rise and mark a line perpendicular to the rise. This is a cut line to allow you to shift the entire set of stairs down. When the treads are installed, this cut will make the bottom step the same height as the others.
Cut the stringer with a circular saw and finish the cuts with a handsaw.
Use this stringer as a template to mark and cut the others.
You may also want to trace the stringer onto composite material to cut two fascia boards that will cover the outside stringers. Use composite boards without grooves.
Cut a board (for this deck a 2 x 8) the width of the steps to support the stringers below the rim or end joist. Use pieces of the same 2 x lumber to attach the board against the bottom edge of the joist.
Use an additional piece of 2 x material to brace the back of the support board against a joist or beam. Attach the braces with joist hangers or decking screws.
Hold the stringers and hangers flush with the top of the 2 x 8 support and mark the each hanger location.
Remove the stringers and secure the hangers to the support board with 10d nails and screws.
Drill pilot holes and attach the outer stringers to hangers with nails and screws. Secure the bottom of the stringers to the bottom posts with screws.
Cut a pressure-treated wood toe kick for the bottom of the stairs. Drill pilot holes and attach it with screws.
Attach the remaining stringers and secure the posts to the bottom of the stringers with bracing, anchors and carriage bolts. Look at How to Build a Deck: Composite Decking and Railings for step-by-step instructions on bracing posts.
Cut the remaining toe kick pieces from pressure-treated wood and composite material without grooves. Remember to cut a composite piece for the bottom of the steps. Cut stair treads from composite decking to overhang the toe kicks by about an inch.
Drill pilot holes and attach the toe kicks, securing treated boards first and covering them with composite boards.
When attaching the composite toe kick elements and the treads, use matching-color composite screws.
Drill pilot holes and secure the treads, using a screw to set a drainage gap between the boards on each step.
For a cleaner look, install composite stringers to cover the outer wood stringers.
The stair railings include vinyl top and bottom rails, as well as balusters.
Slide post sleeves over the posts. Cut the sleeves to length as needed. Glue the collars in place with PVC cement. Follow the package instructions.
Hold a bottom rail against the posts with the baluster holes centered. Mark the angle at each end. You'll need to subtract enough from your measurements to allow space for the two mounting brackets. Cut the rail. Repeat the process with the other bottom rail.
Align the holes on each bottom rail with a corresponding top rail. Transfer the angles to the top rails and cut them accordingly.
Slide the brackets on a bottom rail and mark the bracket locations on the top and bottom posts. Drill pilot holes and secure the rail with screws. Repeat the process with the other bottom rail.
The balusters need be cut to match the angle of the rails. Hold a T-bevel against a post and bottom rail to get the correct angle.
Mark and cut the balusters accordingly.
Place stair baluster inserts in the holes on the top and bottom rails. Attach the balusters to the bottom rail.
Position the top rail and secure it in place with screws.
Finish the railings with post caps and fill in around the footers with gravel or soil.
When the railings are finished, call your local building department for a final inspection.
Always follow the manufacturer's recommendations for fasteners and structural hardware.
Read more about pressure-treated lumber and wood preservatives on the EPA website: