Look, I get it. Stair stringers seem intimidating. That first time I stood in my backyard staring at a pile of lumber trying to figure out how to build stair stringers for my deck stairs, I almost called a carpenter. But after building seven sets over the years (and messing up two), I can tell you it's totally doable if you break it down. Let's cut through the confusion.
What Exactly Are Stair Stringers Anyway?
Stringers are the slanted boards running diagonally under your stairs – they're the backbone that holds everything up. Forget them, and your stairs become a collapsing hazard. There are three main types:
- Cut stringers: The most common type with triangular notches where treads sit
- Closed stringers: Solid boards with treads mounted on top (no cuts)
- Monolithic stringers: Precast concrete beasts for commercial jobs
For 95% of DIYers asking how to build stair stringers, we're talking about cut stringers from dimensional lumber. Get this wrong and you'll have bouncy, uneven stairs that feel like a funhouse ride.
Gear Up: Tools That Actually Matter
Don't waste money on fancy gadgets. Here's what you really need:
| Tool | Why You Need It | Budget Option |
|---|---|---|
| Circular Saw | Making precision cuts in lumber | Basic $60 model (avoid ultra-cheap) |
| Speed Square | Laying out angles & keeping cuts square | Standard aluminum ($10) |
| Carpenter's Pencil | Marking cut lines clearly | Any hardware store pencil |
| Clamps (4 minimum) | Securing stringers during layout | Irwin Quick-Grips ($15 each) |
| Measuring Tape | Critical for rise/run calculations | 25' Stanley ($12) |
That framing hammer collecting dust? Not essential. Fancy laser levels? Overkill. Focus on these core tools when figuring out how to build stair stringers on a budget.
Material Choices That Won't Rot in 2 Years
Choosing wood is where many DIY stair stringer projects go sideways:
| Wood Type | Best For | Price Per 12' Board | Why I Avoid It |
|---|---|---|---|
| Pressure-Treated SYP | Exterior stairs | $18-$22 | Can twist while drying |
| KDAT Cedar | Decks/porches | $35-$45 | Costly but stable |
| LVL Beams | Long spans >10 steps | $75+ | Overkill for most DIY |
| Standard Pine | Indoor ONLY | $10-$15 | Rots outdoors quickly |
The Magic Formula: Rise and Run Calculations
This is the absolute foundation of how to build stair stringers correctly. Screw this up and your stairs become a tripping hazard.
Step-by-Step Measuring
- Measure total vertical height (floor to landing)
- Divide by typical step height (7-7.5")
- Round to nearest whole number (this is # of risers)
- Divide total height by riser count for actual riser height
- Calculate run: Tread depth (10") x number of treads
Here's a real example from my porch rebuild last summer:
| Total Rise | # Risers | Calculated Riser Height | Tread Depth | Total Run |
|---|---|---|---|---|
| 56.75" | 8 risers | 7.094" | 10.5" | 84" |
Cutting Stringers Without Cutting Your Fingers Off
Now the fun part. Grab your carpenter's pencil:
- Mark first riser height on board edge
- Mark tread depth horizontally from that point
- Repeat down the board
- Connect marks to form triangles
- Cut with circular saw (finish corners with handsaw)
Avoid these rookie mistakes I made on stair stringer attempt #1:
- Cutting the top plumb cut too long (ruined the board)
- Forgetting tread thickness in calculations
- Using a dull blade causing tear-out
Stringer Spacing: How Close is Safe?
This depends entirely on your tread material:
| Tread Material | Max Span Between Stringers | My Recommended Spacing |
|---|---|---|
| 2x Pressure-Treated | 16" on center | 12" for less bounce |
| Composite Decking | 12" for most brands | 10" (check mfr specs) |
| 1" Solid Hardwood | 14" | 12" |
Hanging Stringers So They Don't Pull Away
Attaching to the deck header? Don't just toenail them! Here's what actually works:
- Metal Stringer Hangers ($2.50 each): Fast, code-approved, foolproof
- Ledger Board: Bolt 2x12 to rim joist, notch stringers into it
- Bottom Concrete Pad: Must be below frost line with proper drainage
Stair Stringer Building FAQs Answered
How many stair stringers do I need for standard 36" wide stairs?
Three minimum. Even with 2x treads, two stringers cause bounce. Add a fourth if using composite decking.
Can I use 2x10s instead of 2x12s for stair stringers?
Only if your total stair rise is under 5 feet and tread depth is shallow. 2x12s are always safer and less bouncy. I never use 2x10s anymore after one cracked under heavy use.
Why do my DIY stair stringers always squeak?
Three culprits: Wood-on-wood friction (use construction adhesive), loose fasteners (switch to structural screws), or seasonal wood movement (ensure proper wood drying).
How much does it cost to build stair stringers vs buying pre-cut?
| Method | Cost for 3-Step Stairs | Time Required |
|---|---|---|
| DIY Stringers | $55 (pressure-treated) | 3-4 hours |
| Pre-Cut Stringers | $130+ (big box stores) | 20 minutes install |
Pre-cuts save time but cost 2.5x more and rarely match exact measurements.
Disaster-Proofing Your Stairs
After building dozens of stair stringers, here's my survival checklist:
- Check for crowning: Lay boards with arch facing up
- Dry-fit everything before cutting treads/risers
- Seal cut ends of pressure-treated wood
- Use stair gauges ($6) for identical stringers
- Brace temporarily until all stringers are secured
Truth time: My third attempt at learning how to build stair stringers still had a ⅜" height difference between steps. I fixed it by planing down the taller risers – a messy solution. Measure thrice, cut once.
When Building Stair Stringers Isn't Enough
Sometimes DIY isn't the answer. Call a pro if:
- Total rise exceeds 12 feet (requires mid-landing)
- Working with curved or spiral stair designs
- Permit requirements demand engineer-stamped plans
Ultimately, mastering how to build stair stringers comes down to precision and patience. Start with small utility stairs before tackling front entries. And remember – every carpenter has a pile of botched stringers in their past. What matters is what you learn from them.
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