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 | houndog3
Join Date: May 2025 Posts: 1 michigan 
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2025-05-27 201891
I want to build a 14ft wide lean to in michigan,for a steel roof ,can a 2x6 at 24inch on center with a 12 inch fall be ok?can any body point me in a good direction where to find this info,i do not understand the live load math that I have read about,thanks for any input !
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| Tractorpoint
Join Date: Oct 2006 Posts: 20 NJ
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2025-08-01 201904
You're asking a great (and important) question — building a 14-foot-wide lean-to with a steel roof in Michigan must take snow load into serious consideration, and unfortunately a 2x6 rafter, 24" on center, with just a 12" total fall (slope) across 14 feet is likely not strong enough for the typical Michigan snow loads.
🔍 Let's break this down:
❄️ 1. Snow Load in Michigan
Michigan has some of the highest snow loads in the U.S. outside of the Rockies. Depending on your specific location, the ground snow load can range from 30 to 70+ psf (pounds per square foot). For structural design, you'd use the roof snow load, which is often 70-90% of the ground snow load.
Assume 35–50 psf roof snow load unless you’re in the Upper Peninsula, where it can be higher.
🧱 2. 2x6 Span Limits
For a roof with a snow load of 40 psf, the maximum allowable span for:
2x6s at 24" O.C. is around 9 to 10 feet
At 16" O.C., it's a bit more: 10 to 11 feet
But you're proposing a 14-foot span — far beyond what a 2x6 can safely handle under Michigan snow loads.
📐 3. Slope (Pitch)
A 12-inch fall across 14 feet is only a 0.7/12 pitch — nearly flat. A roof with this low of a slope:
Doesn't shed snow well
Must support full snow loads — no reduction due to slippage
So, you cannot reduce the snow load value due to pitch.
✅ Better Options:
✔️ Use 2x8 or 2x10 rafters, or:
Reduce the spacing to 16” O.C.
Increase the pitch to shed snow better (even a 3/12 or 4/12 helps)
Consider a metal I-beam or LVL (laminated veneer lumber) ridge/support beam and hangers for intermediate support
📚 Where to Get Reliable Info
Here are some great resources:
American Wood Council’s Span Calculator (free and reliable):
https://awc.org/span-calculator/
Your Local Building Department
They'll give you the minimum snow load and required rafter specs for your exact area.
Michigan Residential Code (MRC)
Based on the IRC (International Residential Code) — your local building department enforces this.
Books/Guides:
"Graphic Guide to Frame Construction" by Rob Thallon
"Residential Structural Design Guide" by HUD (available free online)
💬 Summary
No, 2x6 at 24" O.C. over 14 feet with low slope is not safe for Michigan snow loads.
Use larger dimensional lumber, reduce spacing, or add intermediate support.
Check with your local building inspector — they're usually very helpful and want you to build safely.
....
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