Low deck stairs with composite decking treads. Deck Basics:

Building Basic Deck Stairs
With Composite Treads
And Risers

In This Article:

Supporting structure is added to the deck frame, stair stringers are laid out to visualize the project, holes are dug for handrail posts, stair stringers are attached, then riser and tread surfaces are installed.

Related Articles:
Skill Level: 2-3 (Basic to Intermediate) Time Taken: About 4 Hours

By , Editor


I recently modified a deck for some friends, and they wanted the stairs relocated after we built an extension to the deck.

The original steps are visible  toward the right-hand side of the picture.


The new stairs will go here, facing a different direction.


The back side of the rim joist.

It helps to have easy access to this area, preferably before the deck surface is installed. Otherwise, I could crawl under the deck and fasten the new structure.


Visualize A New Set Of Steps:

These are the stair stringers that I removed from the old deck, plus some more that I made from 2x12 lumber.

These stringers are barely resting against the rim joist, so I'll need to add some wood below the rim joist to support them.


I screwed these "down-riggers" to the rim joist. These are just scraps of joist material (2x8 in this case) that are twice as long as the depth of the joist. In this case, that means 14½" long.


I attached some 2x8 blocks below the rim joist.


Now the stair stringer has something to push against. I'll call these the "leaner" boards, because the stringers lean against them.


At this point I focused my attention on installing the new deck boards, just because the homeowner preferred it.

Usually I will complete the stair framing and install the stair treads before working on the deck surface, because I like to get the complicated tasks done first.

If the stairs are done before the decking, the stringers can be fastened by driving screws through the "leaner" boards into the backside of the stringers, which is easier than the method I used, which you'll see shortly.


Laying out deck post holes. Using a can of white landscape marking paint, I laid out the location of the handrail posts that will support the bottom of the stairs.

I cut away the sod using a flat-blade shovel and dug holes with a post-hole digger.


I dug the holes about 2½ feet deep, tamped and leveled the soil at the bottom of the hole, and dropped a 12 inch concrete pad into the hole.

I would've set the post in the hole and backfilled it, but there was nothing to hold the post in the proper position, so I had to remove it.


I mounted the outer stair stringers to the deck structure. It's hard to see, but there are two 2x8 blocks fastened to the "leaner" boards. I screwed these stringers to the side of these blocks. Otherwise, I could have used some metal "L" brackets to attach the stringers.


Between these outermost stringers I installed a piece of wood. This happens to be a 2x8, because that's all I had. Given a choice I would have used a 2x6, but this board will be a little stronger, so it can't hurt.


I placed an 8-foot long 4x4 post into the hole and clamped it to the inside corner of the stringer/front board connection.

This was kinda tricky. I had to make sure the flat part of the stair stringer was level (using the little red torpedo level) while simultaneously making sure the post was close to being plumb, then clamp everything together. I just used my foot to lift the stringer while I held a 4-foot level against the post and tightened the clamp.


After the posts were fastened to the stringers with 3-inch deck screws (4 screws on both faces), I backfilled the holes and tamped the soil.


Stair Stringers:

This is one of the 2x8 cleats that the stringers were screwed to...


... like this.

Large metal angle brackets (at least 5 inches long, I'd guess) would also work


The middle two stringers were so close to the neighboring stringers that I could not reach them if I attached the cleat to the deck frame first.

I screwed the stringers to the cleat and then I just tilted the assembly into place.


I fastened the entire assembly to the deck structure with screws.

I also screwed through the front 2x8 board into the stringers, so the stringers were secured front and back.


There are six stringers for a set of stairs that are less than 5 feet long (it's exactly 4 feet between the handrail posts).

Some of these stringers were placed 12 inches on center, and the middle two were 10 inches on center. I could have easily gotten away with 16 inches on center, but I had some extra stringers so I decided to use them.


Covering The Stair Stringers:

I attached a piece of decking to the riser.

I often use two 1x4 treated boards for this surface, but the homeowner wanted a no-maintenance product, so we just used the same deck boards.

The risers were about 7 inches tall, so I will need to rip a thin strip of decking to place above this board.


Then I screwed two pieces of composite decking to the tread portion of the stringers.

Note that the riser surface has already been installed. I always install the riser boards before the treads (unless I'm leaving the risers open).

This riser takes up one inch of the tread space, forcing the tread boards one inch farther forward. But the riser board below provides an additional inch of support for the stair treads, so the net effect is the same.


The lower tread boards needed to be notched around the posts. I used a jig saw to cut the notches.

I made these treads overhang at each end by 2 inches. The homeowner wants to add some pieces of this decking to the sides of the treads to conceal the structure, so that will take one inch of the overhang, leaving a final overhang of one inch.

When I do stairs with wood treads I usually use an end overhang of 2 or 3 inches.



Related Articles:



Tools Used:

  • Cordless Drill/Driver
  • Basic Carpentry Tools
  • Level, 4'
  • Miter Saw
  • Table Saw (or Circular Saw)
  • Jig Saw
  • Shovels
  • Post Hole Digger
  • Tamper, 8"x8"

Materials Used:

  • Treated Lumber, 2x12x8'
  • Treated Lumber, 2x8
  • Treated Posts, 4x4x8'
  • Concrete Post Pads, 12" Wide
  • Composite Deck Boards
  • Deck Screws, 3"
  • Screws for Composite Decking, 2½"

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Written May 11, 2005