Install Wood Deck Stair Stringers and 4×4 Newel Posts

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How to Build Wood Deck Stairs: Install 2×16 stringers, anchor the 4×4 newel posts to the concrete step and build the guard rail with Simpson Strong-Tie metal-wood connectors.

Table of Contents

  1. Planning and Building Wood Deck Stairs with Landing
  2. Tear Down Old Wood Deck Stairs and Landing
  3. Remove Wood Deck Stair Landing Support Posts and Concrete Footers
  4. Build Deck Stair Landing: Pour Concrete Footers and Install 6×6 Posts
  5. Deck Stair Landing: Saw Post-to-Beam Support Notches
  6. Deck Stair Landing Beam and Joist Framing
  7. Deck Stair Stringer Hanger Board and Simpson Strong-Tie LSCZ Stringer Connectors
  8. Install Wood Deck Stair Stringers and 4×4 Newel Posts (you are here)
  9. How to Frame a Wood Deck Stair Landing
  10. Build Wood Deck Stairs – Layout Solid and Sawn Stringers
  11. How to Install Deck Stair Stringers and Treads
  12. Build Wood Deck Stairs and Landing – Completed Job Photos

Install Wood Deck Stair Stringers and 4×4 Newel Posts

The stair steps have been traced, the 2×16 solid stringers cut, Simpson Strong-Tie ABA44Z post bases bolted to concrete anchors:

Build Deck Stairs - Install Solid Stair Stringers

Build Deck Stairs – Install Solid Stair Stringers

The TA9Z-R staircase angles are fastened to the stringer with SD 1/4 x 1-1/2 inch screws for each stair tread. Metal angles or 2×4 ledger blocks are required for solid stringers to support the treads:

Simpson Strong-Tie TA9Z-R ZMax Staircase Angles on Deck Stair Stringers

Simpson Strong-Tie TA9Z-R ZMax Staircase Angles on Deck Stair Stringers

Install Wood Deck Stair 4×4 Newel Posts

The newel posts are mounted on Simpson ABA44Z 4×4 post bases bolted to a 1/2″ x 4-1/4″ concrete wedge anchor in a hole drilled in the concrete step. The post is then fastened to the metal base with six Simpson SD #9 x 1-1/2 inch screws:

Deck Stair 4x4 Newel Post - Simpson Strong-Tie ABA44Z Post Base

Deck Stair 4×4 Newel Post – Simpson Strong-Tie ABA44Z Post Base

Side view of the newel posts, Simpson post base and 2×6 blocking (required by the Deck Code, see Figure 36 “Stair Guard Requirements” on Sheet 19). The newel posts are bolted to the 2×16 stringers with 1/2 inch galvanized bolts. Take care to place the newel-to-post upper bolt high enough that it doesn’t obstruct the 1-1/2 inch thick stair tread:

Deck Stair 4x4 Newel Post to Stringer Connection Detail

Deck Stair 4×4 Newel Post to Stringer Connection Detail

Newel posts and 2×16 stair stringers assembly. The newel posts are extremely rigid with no wiggle. The newel posts are initially sawn about 14 inches taller than required. The tops will be sawn off at the correct height and angle to match the stairs later:

Wood Deck Stair Framing - 4x4 Newel Posts and Cross Blocking

Wood Deck Stair Framing – 4×4 Newel Posts and Cross Blocking

Deck Stair Newel Post Blocking

Simpson Strong-Tie DTT2Z deck tension ties are fastened to the 2×6 cross block and lower 1/2 inch bolts through the newel posts. Tension ties are normally be installed on the upper bolt to better resist lateral loads on the guard postl but that’s not possible here:

Deck Stair Newel Posts - 2x6 Blocking

Deck Stair Newel Posts – 2×6 Blocking

Newel post and cross blocking installation details showing how the bolts, staircase angle and tension tie are installed:

Deck Stair Newel Post Connection Detail - 2x6 Blocking with DTT2Z Deck Tension Tie

Deck Stair Newel Post Connection Detail – 2×6 Blocking with DTT2Z Deck Tension Tie

I place a couple of 2×12 WeatherShield stair treads on the staircase angles to check the fit. (I stained the treads prior to installation because it’s way more convenient.) The uneven concrete step is apparent:

Deck Stair Framing - 4x4 Newel Posts

Deck Stair Framing – 4×4 Newel Posts

The 2×12 stair tread is fastened to the Simpson TA9Z-R staircase angle with two SD 1/4 x 1-1/2 inch screws driven in from the bottom:

Build Deck Stairs - Simpson Strong-Tie Staircase Angle and Deck Tension Tie

Build Deck Stairs – Simpson Strong-Tie Staircase Angle and Deck Tension Tie

Build Deck Stair Guard Rails

The stair and landing guard rails are built next for safety as I’ll be going up & down the stairs as I work my up to the 2nd flight of stairs. See How to Build Code Compliant Deck Railing for details.

Wood Deck Stair Framing - Rail and Guard Post Cross Blocking

Wood Deck Stair Framing – Rail and Guard Post Cross Blocking

Challenges when installing 4×4 guard posts on the stairs are:

  1. The guard posts must be much taller for stairs compared to the landing.
  2. Sawing the post tops accurately to match the stair angle.

My solution is to temporarily install a 2×4 top rail as illustrated in the following diagram using an uncut 10 foot long board:

Build Wood Deck Stairs - Mark 4x4 Guard Posts for Sawing 40 inch Rail Height

Build Wood Deck Stairs – Mark 4×4 Guard Posts for Sawing 40 inch Rail Height

34 inch Stair Guard Height

Figure 36 “Stair Guard Requirements” on Sheet 19 of the Deck Building Code calls out a “stair guard height: 34″ measure from nosing of step“. Compare this to 39 7/8″ in my diagram (see above). The mistake I made was laying out the 2×4 side rail and 2×6 cap rail such that it was more or less flush with the landing guard rail for a smoother transition. The Building Inspector didn’t fault me on this, although your local officials may be more strict.

A taller stair guard rail may be safer (more challenging to fall over the rail) but the main reason for a 34 inch stair guard height is placement of the hand rail at a height where it’s easier to grasp. See Sheet 20, Figure “Handrail Requirements” in the Code requirements at the prior link.

The correct way to build a 34 inch stair rail is shown in the following diagram. The stair rail mounts much lower compared to the landing rail as noted in the yellow circle:

Build Wood Deck Stairs - Mark 4x4 Guard Posts for Sawing 34 inch Rail Height

Build Wood Deck Stairs – Mark 4×4 Guard Posts for Sawing 34 inch Rail Height

Because I build everything with screws, I could lower my rail by:

  • Disassemble the stair rail and saw the stair guard posts shorter.
    The busy work is sawing the many 2×2 pickets to match.
    – or –
  • Install 2×4 blocks below the top rail at each stair post, then mount the aluminum handrail lower at 34 inches.

The steps for marking and sawing the sloping top of the guard posts for a 34 inch rail are:

  1. The interior guard and newel posts are sawn 4 feet long, which is taller than the final dimension.
  2. Install the two guard posts at the top of the stair landing per the standard dimensions (the landing is a free standing deck in terms of the Deck Code):

    Wood Deck Rail with Pickets Profile Drawing

    Wood Deck Rail with Pickets Profile Drawing

  3. Permanently install the 4 feet tall 4×4 guard posts along the stairs with 1/2 inch galvanized bolts and nuts.
  4. Get a helper to hold the other end of a 10 foot long 2×4 at the stair landing.
    This is a stand-in for the top rail.
  5. Hold the 2×4 against interior faces of the newel post and landing guard post.
  6. Place a 2x block on the 2×4.
    This represents the 1-1/2 inch thick cap rail. See the following image for details.
  7. Raise the 2×4 and 2x block until it’s 34 inches high above the nose of the bottom step.
  8. Hold the 2×4 top rail against the newel post while your helper raises the far end until it’s 34 inches above the nose of the top stair.

    Mark Stair Guard Posts for 34 inch Rail Height

    Mark Stair Guard Posts for 34 inch Rail Height

  9. Fasten the 2×4 to face of the newel post with a single screw.
    This allows the bottom end of the 2×4 to swing up & down for adjustments.
  10. Raise or lower the far end of the 2×4 until the 34 inch step nose to rail measurements are the same.
    The 2×4 is now parallel to the stairs.
  11. Fasten the other end of the 2×4 to the 4×4 guard post at the stair landing with a single screw.
  12. Mark a line on the 4×4 guard and newel posts using the slope of the 2×4 top rail as a guide.
  13. Remove the 2×4 top rail.
  14. Cut off the top of guard and newel posts following the sloping marks with a circular saw.
    The posts are not difficult to saw freehand.

This procedure eliminates a lot of guesswork.

Next up: How to Frame a Wood Deck Stair Landing.

Thanks,

Bob Jackson

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