Episode 8 – Wood Stair Construction

It Starts With The First Step

This was difficult to visualize from only the stair floor plans. Walk through the stair project and take a look at the design plans below to compare the design to the installation.

Here we see the first step formed. It’s pressure treated wood on concrete to prevent deterioration. Take note of the felt paper in the below photos to further protect the wood from the concrete’s moisture.

This staircase design plan has steps formed from (2) sides. The final design will have the first run of stairs flanked by walls, followed by glass handrail above.

Time Lapse

See how the stairs were formed from step 1 to the final stringers.

Woodworking Makes This Possible

Standard 2X Southern Yellow Pine wood stringers are notched to form the stairs.

It’s important not to notch so much as to weaken the strength of the stairway and cause excessive deflection or splintering of wood under high loads. This is all calculated by the engineer. 

Three stringers are used in this short stair run to support the 2 stringers.

Posts, Ledgers, & Stringers

The intermediate stair landing is formed by using a double 2X wood ledger beam anchored to the masonry wall. 

4 X 4 (pressure-treated) wooden posts support the landing & are secured above & below.

Wood stringers are formed using hangers to the ledger and wood girder to support the plywood above.  See more in the close-ups and quick clips below of the wood stair construction process.

Staircase Construction Close-Up

More about the parts that make up the masonry walls. Click/Press photos to zoom in.

A double 2X ledger is fastened to the masonry wall using Red Head Anchors.

Learn more about the anchors below. 

Simpson Joist Hangers are used to connect the stringers to the ledger beam. These are designed by the project engineer to handle the code-specified loads & specified on the plans. 

4 X 4 Wood posts hold the intermediate landing to the slab below using Simpson connectors & straps. 

A Simpson ABU44Z Galvanized post base is used to secure the wood post to the concrete slab. The post base keeps the wood elevated above the concrete to prevent contact with moisture. 

About The Anchors Used

ITW – RedHead concrete expansion anchors were used to attach the double 2X wood ledger to the masonry wall. 

These anchors have a tip that expands in the wall when the nut is tightened to provide the grip needed. 

The length & diameter of the anchor is specified by the engineer to support the code-required loads & should be installed to solid concrete or filled masonry per the manufacturer’s specifications to provide the allowable rated load resistance.

Quick Clips From The Field

Understand the stair building process from up-close and personal footage of the installation. 

Staircase Construction Field Plans

The installers work off of a set of field drawings to calculate the steps, rises, and runs as well as all the notches and fittings needed.

This is an art as much as a science, and experienced carpenters handled this complex design with precise measurements.

 

Technical Corner - Plan Tutorial

The Engineering Behind The Plan

Learn to read the stair construction plans

Plan Page: Staircase Design Details

A few highlights to point out from this difficult plan set to build from:

  1. Second-floor plan view of the stairs. the upper part of the drawing is the lower part of the stairs, rising up to the second floor.

  2. Wood stringers that are notched to form the rise and run of the stairs.

  3. Detail of the wood ledger as photographed on this page.

  4. Stair landing in section view on the plans. Notice how different the actual construction is from the intention of this photo, but that’s how the job is done.

  5. Section of the upper stair stringers to the second-floor trusses. Most notable is the glass rail which will be explained during installation.

 

Stair Plan Details. Click/press the image to enlarge

The Engineering Behind The Plan, Explained:  

Wood stairs follow required design loads from the respective building codes (see for example FBC/IBC Table 1607.1). Stairs also need to meet egress requirements which can be seen for example in IBC/FBC 1011 & related sections.

Deflection is a primary concern to provide a ‘safe feeling’ for those who use the stairs.

Wood design follows the American Wood Council National Design Standard for Wood Construction (NDS) 

What's Next?

While we wait for the upper floor beams to be poured & roof trusses to arrive, take a look back at our previous construction articles and catch up on some exciting moments.

We’re also finishing up some new formats to present the next stages of construction to you as we enter more detail and design after the shell completion.  Stay tuned!

Read Our Stair Handrail Article

In this remodel project, we retrofit an old picket-style handrail with a modern glass railing.

Follow along with the process and see the incredible finished product.

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