Online Gable Truss Builder - Create and Visualize Gable Truss Plans
Design and customize your gable truss structures with our Online Gable Truss Builder. This dynamic tool offers comprehensive capabilities to create detailed gable truss plans, visualize all components and angles in, and manage cut lists for all parts efficiently. Perfect for construction professionals and DIY builders, it allows for precise planning and modification of gable trusses. Export your finalized truss designs as blueprints or PDFs and enjoy the convenience of printing directly from the platform. Streamline your truss construction projects with precision and ease.
How to Use This Tool
Enter span, pitch, and overhang
Type the outside-to-outside span of the bearing walls, the pitch (for example 4/12), and the overhang length. The truss profile draws instantly with top chords, bottom chord, and heel geometry.
Choose the web layout
Pick a king post, queen post, fink, or gable-end style web arrangement depending on span and whether the truss carries sheathing nailers for a gable end wall.
Check every angle and member in the viewer
Click any chord or web to read its length and end-cut angles. The plumb cut at the peak, the heel cut, and every web bevel are dimensioned on screen.
Export the cut list and blueprint
Generate the full cut list with quantities for a run of identical trusses, then print or download the blueprint PDF to build from on a flat deck or driveway.
Gable truss geometry
A gable truss is two common rafters (top chords) closed with a bottom chord, so all the standard rafter math applies. The top chord length is the half-span run times the pitch multiplier, and the peak plumb cut angle equals the pitch angle: arctan(pitch/12). At the peak the two chords meet at 180 degrees minus twice the pitch angle, so each chord takes the same plumb cut you would put on a common rafter.
Webs are solved as triangles hung between the chords. A king post is simply the rise at center; queen posts stand at the quarter points where their height is half the full rise. The tool dimensions every web cut so nothing gets bevel-guessed on the saw.
run = span / 2
top chord length = run x sqrt(1 + (pitch/12)^2)
rise (peak height above bottom chord) = run x pitch / 12
peak plumb cut angle = arctan(pitch / 12)
king post length = rise (less chord depth adjustments)
queen post height at quarter point = rise / 2
Worked example: 24 ft span king post truss at 4/12
- Span 24 ft, so the run is 12 ft. Pitch is 4/12, so the pitch angle is arctan(4/12) = 18.43 degrees.
- Pitch multiplier: sqrt(1 + (4/12)^2) = sqrt(1.1111) = 1.0541. Top chord line length = 12 x 1.0541 = 12.65 ft, about 12 ft 7-3/4 inches from heel to peak centerline.
- Rise at center = 12 x 4/12 = 4 ft above the bottom chord line, which sets the king post length before deducting for chord depths.
- Cut both top chords with an 18.43-degree plumb cut at the peak and the matching heel cut at the wall end; the bottom chord is a straight 24 ft plus any overhang detail.
- Build one truss on a flat deck, check it against the blueprint, then use it as the template for the rest of the run. The exported cut list shows quantities for however many trusses you enter.
Frequently Asked Questions
Can I build my own roof trusses instead of ordering them?
For sheds, garages, and outbuildings, site-built trusses are common and this tool gives you the geometry and cut list to do it. For habitable dwellings, most jurisdictions want engineered trusses with a stamped design, because plate-connected trusses are proprietary engineered products under IRC R802.10. Gusset plates you cut from plywood can substitute for metal plates on small spans, but check with your building department before framing a house roof with them.
What is the difference between a king post and a fink truss?
A king post truss has one vertical web from the bottom chord center to the peak - simple, and fine for spans up to roughly 16 ft. A fink (W) truss replaces the single post with four diagonal webs in a W pattern, which shortens the unsupported length of both chords and is the standard for residential spans of 20 to 33 ft. The builder lets you switch layouts and instantly redraws the web lengths and bevels.
What angle do I cut the top chords at the peak?
The plumb cut equals the pitch angle: arctan(pitch/12). That is 18.43 degrees for 4/12, 26.57 degrees for 6/12, 33.69 degrees for 8/12, and 45 degrees for 12/12. Set your miter saw to that angle measured from square. Both chords get the same cut and meet on the vertical centerline. The tool prints the exact angle for your pitch on the blueprint, along with the heel cut at the wall end.
How is a gable-end truss different from a common truss?
A gable-end truss sits over the end wall and carries little roof load, but it needs vertical studs (nailers) at 16 or 24 inches on center to attach the wall sheathing and siding, instead of the W-shaped structural webs. Its profile matches the common trusses exactly so the roof planes stay straight. Select the gable-end layout in the builder and it swaps the webs for evenly spaced studs with their lengths in the cut list.
How much overhang can the truss tail carry?
Overhangs of 12 to 24 inches are routine as cantilevered extensions of the top chord. Beyond about 24 inches, the tail starts to need a larger chord or additional support, and wind uplift on the soffit becomes a design consideration. Enter your overhang in the builder and it extends the top chord and adjusts the tail cut. For engineered trusses in permitted dwellings, the truss designer must account for the overhang - verify locally.
Do site-built trusses need collar ties too?
No - a true truss already ties the rafter feet together with the bottom chord, which is what resists spreading. Collar ties per IRC R802.4.6 belong to stick-framed rafter roofs, where they resist wind uplift at the ridge when installed in the upper third of the attic space. If you are framing with individual rafters and a ridge board instead of trusses, use the roof builder and add rafter ties or collar ties as your code official directs.
Can I modify a truss after it is built, like cutting a web for storage?
Never cut a truss web or chord without an engineered repair detail. IRC R802.10.4 prohibits alterations to trusses unless approved by a registered design professional, and a single cut web can drop the capacity of the whole truss. If you need attic storage space, design for it up front: an attic truss with a widened center bay, or a gambrel profile. The gambrel truss builder is built exactly for that case.