Mono Truss Calculator
Estimate monoslope truss pitch, top chord length, gravity reaction, uplift reaction, deflection screening, and a practical material takeoff from span, spacing, loads, pitch, and layout assumptions.
📌Mono Truss Presets
🔧Truss Geometry And Loading
Mono Truss Results
Calculation Breakdown
🧱Material And Spec Grid
📊Mono Truss Reference Tables
| Roof Use | Common Span | Typical Pitch | Screen Load Range |
|---|---|---|---|
| Patio cover or porch roof | 8 to 14 ft | 2:12 to 4:12 | 20 to 35 psf |
| Carport mono truss | 12 to 22 ft | 2:12 to 5:12 | 25 to 45 psf |
| Lean-to storage shed | 8 to 16 ft | 3:12 to 7:12 | 20 to 40 psf |
| Snow region utility roof | 10 to 20 ft | 4:12 to 8:12 | 45 to 80 psf |
| Chord Member | Actual Depth | Best Screening Use | Watch Point |
|---|---|---|---|
| 2x4 chord | 3.5 in | Small sheds and covers | Heel bearing and webs |
| 2x6 chord | 5.5 in | Moderate mono trusses | Compression bracing |
| 2x8 chord | 7.25 in | Longer or heavier roofs | Plate capacity |
| Glulam chord | Engineered | High load trusses | Supplier design data |
| Species Or Grade | Approx Fb | Approx E | Use In Calculator |
|---|---|---|---|
| SPF No. 2 | 875 psi | 1.4M psi | General framing |
| SPF No. 1 | 1150 psi | 1.5M psi | Better screening margin |
| Douglas Fir-Larch No. 2 | 900 psi | 1.6M psi | Common truss lumber |
| Southern Pine No. 2 | 1100 psi | 1.6M psi | High stiffness option |
| Check Item | Rule Of Thumb | Calculator Output | When To Escalate |
|---|---|---|---|
| Roof slope | 2:12 minimum for many panels | Pitch and angle | Low slope waterproofing |
| Support reaction | Must land on bearing path | Gravity load per heel | Point loads on headers |
| Wind uplift | Connector governs often | Uplift per heel | Open-sided structures |
| Deflection | Finish controls limit | L/180 to L/480 | Ceilings or brittle roofing |
💡Calculation Tips
If you’ve ever owned a shed, the story begins with an imagined roof line, but by the time lumber shows up, it’s clear the actual structure need modification. That mono truss may look like a single diagonal plane between two walls, one high, one low, but as they say, what looks easy geometrically can be tough when it comes to load paths.
Before you grab a single board, you have to be able to tell how hard that top chord will be working. To do that, you’ll put some assumptions about load into the calculator above, enter your span and it does the math for you. Abstract physics becomes actionable measurements for your build.
How to Plan Your Shed Roof Properly
Steeper equals stronger, right? No, its more about water runoff than anything else. What kind of shingles will you be putting on? Asphalt shingles require at least some rise to ensure water doesn’t creep beneath the tabs. You can enter pitch either by angle or ratio. This is nice if you are copying specs from a plan where they use different conventions.
It’s not just about looks. The pitch establish how long your top chord must be, thereby affecting your waste factor and lumber expenses. Mess up here, and you’ll find yourself cutting extra pieces or grappling with ugly butt joints that compromise the structure.
The devil is in the span and spacing. A standard twenty-four inch spacing work for most residential sheds. But that’s based off assuming equal loading over all of the roof area. If you up the span with no change in the chords, you create an exponential increase in the bending moment on the lumber. That’s what the calculator checks against deflection limits. Options range from L/180 for basic functional roofs to L/360 for plastered ceilings.
Why does it matter? Because a sagging roof look awful, but worse, cracks drywall and undermines flashing details at the eaves. You need strength, yes, but also stiffness.
Beyond this, there’s another detail that can get missed: Load combinations. For dead load, we’re looking at combined weight of the truss plus whatever it carries (roofing materials, sheathing). And live load? That’d be maintenance people walking around on the roof or snow accumulating. Mono designs are particulerly vulnerable to wind uplift, with that whole roof serving essentially as a sail attempting to pull away from the low wall.
The software compute independent reactions for both uplift and gravity, flagging areas where you’ll want the highest strength connection. Remember, most failures occurs at the heel joint. Not in the middle of the span. This means you must check the uplift connector load and the bottom chord compression equally.
It all comes down to material selection. An eighteen foot long carport with a heavy snow load won’t stand up well on 2×4’s but that same size greenhouse roof may work just fine. That’s where the reference tables on the page come into play, linking common lumber grades to their appropriate span range. Standard spruce pine fir is not as stiff than Douglas fir. That can mean the difference between needing to check for deflection or not. If you have access to better wood, upgrading the grade is usually less expensive then upsizing the dimension.
Take these numbers with a grain of salt! It is not an engineering stamp, far from it. It’s a preliminary tool for checking load distribution and overall geometry. It’s something to help you prevent major mistakes prior to hiring a professional engineer or ordering materials. You should of used this before you start building. Seismic requirements, soil conditions in each area, and wind zone will vary depending on where you live. The calculator is meant to fine-tune the answers, not the permit application.
The math of a mono truss roof is one part arithmetic and one part ambition; you want a lot of open space, but the wood only goes so far. Running these numbers up front makes sure that your wishes are grounded in something other than wishful thinking. That diagonal line seems straightforward enough, until you realize how carefully you have to pay attention to all the details to keep it straight.
