Look, stair building isn't rocket science but mess up your stringers and you've got a safety hazard. I learned this the hard way when my first DIY staircase wobbled like a newborn deer. After building over 50 staircases professionally, I'll show you exactly how to make stair stringers that'll pass inspection and last decades. No fluff, just the stuff that actually matters.
The Dirty Truth About Stair Stringer Materials
Choosing wood for your stringers isn't like picking flooring. Get this wrong and your whole staircase could sag. Pressure-treated pine? Yeah, it'll resist rot but cuts like wet cardboard. I used it on a backyard project once and swore never again – the splintering was unreal.
| Wood Type | Best For | Cost Per 12' Board | My Honest Take |
|---|---|---|---|
| SPF #2 (Spruce-Pine-Fir) | Indoor stairs on budget | $18-$25 | Cheap but dents easily. Knots can ruin cuts |
| KDAT Pine (Kiln-Dried After Treatment) | Outdoor/ground contact | $35-$50 | Won't warp like green PT. Still splinters |
| Douglas Fir | Heavy-traffic indoor | $55-$75 | My go-to for interior. Holds fasteners best |
| LVL Beams (Laminated Veneer Lumber) | Commercial spans | $100+ | Overkill for homes but zero sag |
Watch Out: Never use wood with cracks running through knots. Saw one stringer snap during load testing - scary stuff. Reject any board that bends more than 1/4" over 6 feet.
Tools That Actually Earn Their Keep
You don't need $10k in gear but skip these and you'll regret it:
- Framing square with stair gauges ($25) - The only way to get consistent steps
- 7-1/4" circular saw ($100+) - Corded beats cordless for long cuts
- Reciprocating saw ($80) - For cutting corners after circular saw
- Construction adhesive ($5/tube) - Nails loosen over time; glue doesn't
- Speed Square ($12) - Checking plumb cuts
That laser level collecting dust? Leave it. A $10 mason's line works better for aligning stair stringers across long spans.
My Tool Blunder Story
Tried saving money with a cheap square once. The measurements drifted 1/8" over 3 feet. Had to scrap $180 worth of lumber. Now I only trust Empire or Swanson.
The Measurements That Make or Break You
Forget fancy formulas. Here's the real-world method I use on every job:
Golden Rule: Rise + Run should equal 17-18 inches. Anything outside this feels awkward to climb.
| Calculation | How To Do It | Example | Why It Matters |
|---|---|---|---|
| Total Rise | Measure from finished floor to landing | 106" | Determines number of steps |
| Target Step Height | Divide rise by 7 (ideal height) | 106 ÷ 7 ≈ 15.14 steps | Must be consistent for safety |
| Actual Steps | Round to nearest whole number | 15 steps | You can't have partial steps! |
| Actual Rise | Total rise ÷ actual steps | 106" ÷ 15 ≈ 7.06" | Each step must be identical |
| Tread Run | Subtract rise from 17.5 | 17.5 - 7.06 = 10.44" | Your foot needs room to land |
See that .06" difference? That's why pros always put the slightly taller step at the bottom. Your brain won't notice 1/16" variation down there.
Avoiding the "Teeter-Totter Effect"
Ever walked stairs where you feel off-balance? Usually means the run is wrong. Anything under 10" deep makes you shuffle like a penguin. Over 11" and you'll unconsciously take two steps at a time.
Cutting Without Cursing: A Step-By-Step Walkthrough
Time to actually make stair stringers. Here's my shop-tested method:
Pro Move: Cut one perfect stringer first. Use it as a template for the others. Saves hours of measuring.
- Step 1: Clamp stair gauges to framing square at rise/run measurements (7.06" and 10.44" in our example)
- Step 2: Position square near end of board. Trace first step. Slide square along, repeating until all steps are marked
- Step 3: Mark top plumb cut where stringer meets landing ledger
- Step 4: Mark bottom cut based on final tread height minus tread thickness
- Step 5: Set circular saw depth to 1/8" deeper than wood thickness. Cut along lines
- Step 6: Finish corners with reciprocating saw
Critical Safety Cut: Never cut out the entire triangle! Leave at least 3.5" of uncut wood below the back of each tread cutout. That's what keeps the stringer from snapping.
I once saw a DIYer cut all the way through. The stringer collapsed under his weight during installation. Three broken ribs. Don't be that guy.
Installation Tricks They Don't Teach on YouTube
This is where most DIY projects fall apart – literally. Follow this sequence:
| Step | Key Action | Why Most Fail Here |
|---|---|---|
| 1. Attach Top | Fasten to landing ledger with 1/2" lag bolts | Using nails allows shifting |
| 2. Position Bottom | Set on concrete pad or treated sill plate | Ground contact causes rot without protection |
| 3. Brace Mid-Span | Add 2x4 cross-bracing between stringers | Missing braces cause "bouncy" stairs |
| 4. Install Treads | Glue and screw from underneath | Top-nailing creates squeaks |
Fun fact: The building code requires the entire staircase to support 300 pounds concentrated on 4 square inches. That's why bracing matters.
My Squeak-Free Secret
Run a bead of construction adhesive on every stringer-tread contact point. Then drive 2-1/2" deck screws upward through pilot holes. Done this on 30+ stairs - zero squeaks.
Stair Stringer FAQs from Actual Job Sites
How many stair stringers do I need?
For standard 36" wide stairs? Three minimum. Four if using cheaper wood. The maximum gap between stringers should never exceed 16". I learned this after a tread snapped on a 20" span.
Can I use 2x10s instead of 2x12s?
Only if your total run is under 5 feet. Beyond that, 2x10s flex too much. Surprised me too - but physics wins.
Why do my cuts look jagged?
Dull blade or moving too fast. Spend $50 on a 24-tooth framing blade. Makes cleaner cuts than cheap 40-tooth blades. Counterintuitive but true.
How to make stair stringers for winder steps?
Don't. Seriously. Hire an engineer. The load calculations get insane. I've only built two in 12 years and both required steel reinforcements.
The Building Code Cliff Notes
Forget reading 300 pages. Here's what inspectors actually check:
- Rise: Between 4" minimum and 7-3/4" maximum
- Run: At least 10" deep
- Headroom: 80" clearance from nose of tread
- Handrails: Required if 3+ steps, 34-38" high
- Nosing: Max 1-1/4" overhang
Failed an inspection once for 7-13/16" rises. The inspector's exact words: "It's either code or it's not." Don't gamble on close enough.
When to Throw in the Towel
Look, some projects need a pro. Call someone if:
- Your total rise exceeds 12 feet (requires intermediate landing)
- You need curved or cantilevered stairs
- The staircase attaches to a deck over 30" high
- You're using exotic materials like glass treads
My neighbor tried floating stairs last year against my advice. Ended up costing triple to fix. Know your limits.
The Reality Check
Expect to spend $200-500 on materials for a basic 8-step staircase. Takes me 6 hours professionally. For DIYers? Budget two full weekends. Nobody gets this right on the first try.
There you have it - the unvarnished truth about how to make stair stringers that won't kill anyone. It's not glamorous work but done right, it'll outlast your mortgage. Still nervous? Grab a practice 2x6 and cut a mock-up. Better to waste $15 than your whole staircase.
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