Most of the custom homes I build have two stories and therefore require a set of stairs, and, except for a wrought iron spiral job, every staircase gets built on site. To make it easy to remember all the nuances of stair framing, I use a three-stage building checklist that helps me stay on track as I go along. The checklist is based on fundamentals that work on all sets of stairs, no matter what style.
Stair Calculation and Measurements
1. Check the Codes: Before I start anything I refresh myself on building code requirements for stairs and look for any recent changes.
2. Confirm Correct Stairwell Dimensions: I check the stair opening dimensions shown on the plans while the floor joists are being installed. If there is plenty of space for adjustments, I will often build to plan. On the other hand, if there is a wall above and aligned with the end of the stairwell, I check right away to make sure there is enough headroom under the header.
3. Ensure Proper Headroom: In order to build the stairwell correctly, I first need to determine the headroom at the head-out location. Check headroom by measuring diagonally between the header and a straight edge held across a few of the tread nosings, not vertically off the treads themselves.
4. Measure Rise and Run: To determine headroom and pinpoint the location of the stairwell header, I lay out a line on the wall or walls that the stair horse (also called a stringer or carriage) will be attached to. To arrive at this line, I need to measure the overall rise of the stair and overall run. I also check the plans to see where the stairs are supposed to end.
5. Follow Rules of Thumb: Try to keep the rise for each step no higher than 7-5/8 inches, and the run or tread no more narrow than 10 inches. It's good to build a comfortable set of stairs anywhere from 32 to 35 degrees, typically stairs where one tread and one riser add up to between 17 and 18 inches.
6. Determine Tread and Riser: Using the above information and the measured total rise and total run, I calculate the tread and riser needed to make the set fit in the given dimensions. The Construction Master Pro is my tool of choice for these calculations. I adjust the riser and tread until I get an acceptable slope and end up with the start of the first step close to the plan location. I can now pinpoint my headroom and have established the beginning layout for the stair horse.
Stair Horse Layout and Cutting
7. Choosing the Material: I try to avoid the standard 2x12 Douglas fir solid-sawn lumber for my stair stringers, and use Timber Strand 1-3/4-inch LVLs whenever possible.
8. Finish Floor Compensation: Although I have previously calculated the stair riser and tread, I double-check the finish floor thickness on the first and second floor. If there's a difference that will affect the first and last risers, I make needed adjustments. Now's the time to catch this common mistake.
9. Framing Square and Gauges: Use a quality framing square and a decent set of stair gauges for layout. My stair gauge of choice, hands down, is the long-style L.S. Starrett model ST-SGF-111.
10. Marking Treads and Risers: A thick pencil line isn't the best for accuracy; I use a scratch awl to mark out the locations of my treads and risers. I lay out more treads and risers than needed, which allows for proper detailing of the top and bottom riser. I count out and number each riser and tread, making sure there is always one more riser than the number of treads.
11. Calculating Deductions: The bottom riser must always be reduced in height by the thickness of the tread. This allows the first step to conform to the rest; otherwise, it will be taller by the thickness of the tread. The cut is made on the level part of the stair horse that sits on the deck. When I make my plumb cut at the top of the horse where it will sit against the header, I remove an additional thickness equal to the finish riser material. Then I don't have to pad-out the framing when I attach it.
12. Laying Out Your Pattern: Once you've cut and tested your first stringer, use it as a pattern to mark the other stringers, like you would do with a rafter pattern.
13. Cutting: Cut close to, but not past, your layout lines, and finish your cuts with a sharp hand saw. Over-cutting can weaken the stair horses.
14. Framing for Finish: Before I install the stair horse that runs along the wall I pad-out the studs with a few long 2x4s equal to the length of the stair horse so the drywall and stringer trim can slip between the rough stair horse and the wall studs.
15. Connectors at the Landing: The attachment to the landing can involve many different framing options. Depending on the framing situation, I always make sure to have Simpson Strong-Tie A34/A35 or other similar metal connectors on hand to ensure a positive connection. Unless directly supported by a wall below, the connection at the landing needs more than angled nails.
16. Attachment to the Floor: Solid support at the floor requires a 2x4 notched into the bottom of the stair horses. This allows a kick plate-type resistance and can be nailed to the subfloor or, in the case of a slab, be attached to anchor bolts or by shot pins.
17. Draft Blocking: Staircase framing creates all kinds of fire-draft blocking challenges, so I make sure to block out all areas required before I have tons of framing in the way.
18. Fasteners and Adhesives: I always glue and screw the treads and risers, no exceptions. I install the risers first so I can run a few screws through the backside of each riser into the butt edge of the tread below for extra support.
19. Strength and Noise: Once built, I run up and down the stairs looking for bounciness or squeaks. This is the one and only time they can be dealt with affordably.
Don Dunkley is a framer from Cool, Calif., and construction events manager of Hanley-Wood's JLCLive! show and The Remodelers' Show.