Construction glossary · Wood framing
What is truss in construction?
A truss is a pre-engineered, factory-built roof or floor frame made of dimensional lumber webs and chords connected by metal plates, delivered ready to set. In roof framing it replaces stick-built rafters and ceiling joists with a single component spanning wall to wall. Trusses are spaced at a set on-center dimension and counted off the truss layout.
Updated June 2026 · Reviewed by the Ruh construction team
Roof trusses across a building
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Book a walkthroughA roof truss carries the roof load across a clear span using a triangulated arrangement of top chords, bottom chords, and internal webs, joined at the panel points with stamped metal connector plates. The truss manufacturer engineers each profile to the span, pitch, loads, and bearing conditions, then ships a sealed layout and placement plan. For the estimator, trusses are a supplied component: you are not buying loose 2x lumber, you are buying a count of engineered units plus girder trusses, hangers, and bracing. Common spacing is 24 in OC, which lets the roof sheathing and ceiling drywall span without extra framing. Trusses go up fast, give predictable material, and remove most cutting from the roof, but they limit attic use and lock the roof geometry once the package is engineered. The takeoff is a count along the building length plus special members at hips, valleys, and openings.
Trusses are counted as each, off the truss placement plan or, in early budgeting, off the roof framing plan. Read the building length along the ridge line, the on-center spacing (almost always 24 in OC), and any gable-end and girder trusses called out separately. The count is the run length divided by the spacing, plus one for the starting truss, plus the gable ends. Add girder trusses at load points, hip and valley sets, and any doubled trusses under point loads. Bracing lumber, metal connector hardware, and hangers are taken off the engineering package. Confirm the bearing length and overhang from the truss profile, not the wall plan.
Worked example
A 60 ft long building, common trusses at 24 in OC (2 ft). Field trusses = 60 ft / 2 ft = 30 spaces, which gives 30 + 1 = 31 trusses to cover the run. Then add the two gable-end trusses: 31 + 2 = 33 total trusses on the roof. Say the layout also calls for 1 girder truss at an interior bearing and a 2-ply condition there, adding 1 more leaf: 33 + 1 = 34 truss units to order. At an illustrative supplied price of 165 dollars per common truss, the 33 commons run 33 x 165 = 5,445 dollars before the girder, hardware, and freight, which are priced from the truss vendor quote.
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How Ruh handles truss
Ruh reads the roof framing plan or truss placement plan, picks up the building length and 24 in OC spacing, and does the count: field trusses by run divided by spacing plus one, plus gable ends and any girder or doubled members flagged on the layout. It prices the units against your truss vendor pricing in your price book. The estimator checks the count against the engineered placement plan and signs off before the order goes to the plant.
See framing estimating softwareTruss: frequently asked questions
How many trusses do I need for a 60 ft building at 24 in OC?+
60 ft divided by 2 ft spacing is 30 spaces, so 31 common trusses cover the run. Add the two gable ends for 33, then any girder or doubled trusses the layout calls out.
Do I count gable-end trusses in the spacing?+
No. Run the field trusses by length divided by spacing plus one, then add the gable ends as separate units. They are built differently, often with vertical studs for siding, and are priced on their own line.
Can I take off trusses before I have the engineered package?+
You can budget a count off the roof framing plan using length and spacing. The final order must follow the sealed truss placement plan, since girders, hips, and doubled members change the count and price.
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Figures on this page are illustrative. Construction estimates depend on project-specific conditions, source documents, market pricing, and professional judgment. Ruh's AI assists the estimator and does not replace professional review: your team reviews, validates, and approves every estimate, bid, and pricing decision.