Roof truss sizes for U.S. residential construction follow a small set of standard profiles, dimensions, and pitch combinations. Trusses are pre-engineered triangular wood assemblies that span wall to wall, replacing site-built rafters in roughly 80% of new U.S. residential construction. They are manufactured in factories under quality-controlled conditions, delivered to the site as completed assemblies, and installed in a single day on a typical residential project.
Roof truss sizes — also searched as roof truss dimensions, truss dimensions, roof truss measurements, or truss design dimensions — really mean three things: the span (the horizontal distance between supporting walls), the pitch (the rise per 12 of run, which determines how tall the truss is), and the profile (the geometric arrangement of webs that determines what loads the truss can carry). The roof trusses span chart below covers the standard combinations; the 2x4 roof truss span chart covers the most-common residential lumber size; and the section on rafter truss design covers when trusses replace conventional rafter framing.
This guide covers each variable, common truss profiles, typical residential ranges (including specific cases like 30 foot 4 12 truss dimensions and 4 12 pitch truss dimensions which appear frequently in builder questions), what to expect for cost and lead time, and when to choose stick framing instead.
Common residential truss types
Most U.S. residential roof trusses fall into a handful of standard profiles. The differences between them come down to web geometry — the diagonal members between the top chord (rafter) and bottom chord (ceiling joist) that distribute loads.
Common (King-post) truss is the simplest profile — two top chords meeting at a peak, a bottom chord, and a single vertical king post connecting the peak to the middle of the bottom chord. Used for short-to-medium spans up to 24 feet. Cheapest truss to manufacture but limited in span capability.
Queen-post truss is like the king-post but with two vertical posts (one each side of center) plus a horizontal strut between them. Spans 24-35 feet typical. The added webs allow longer spans without increasing top-chord depth.
Fink truss is the most-common modern residential truss profile. Webs form a W shape with the longest diagonal running from the bottom chord midspan up to a top-chord intermediate point, mirrored on each side. Spans up to 40 feet typical, with engineered designs going to 60+ feet. Material-efficient — the W geometry uses smaller web members than a king-post for the same span.
Howe truss has webs forming an N pattern. Less common in residential but standard in light commercial and agricultural buildings. Performs well in long-span applications.
Attic truss is a specialty profile with the web pattern shaped to leave a clear interior "room" — typically 24 by 60 inches usable space — for finished-attic designs. Costs 30-50% more than equivalent fink trusses but provides usable second-story space without conventional framing.
Scissor truss has a sloping bottom chord rather than a horizontal one, creating cathedral-ceiling space in the room below. The bottom-chord pitch is typically half the top-chord pitch — a 8/12 top with a 4/12 bottom is a common spec.
Roof trusses span chart and 2x4 roof truss span chart
The roof trusses span chart below covers the most-common residential combinations of lumber size, pitch, and span. These are starting values for typical residential snow loads (under 30 psf) — actual specifications depend on local snow load, wind exposure, and ceiling load. Always verify against the engineered truss calculation for your specific project.
2x4 roof truss span chart (Spruce-Pine-Fir #2 grade, 24-inch on-center spacing): up to 24 feet for common (king-post) truss; up to 28 feet for fink truss at 4/12 pitch; up to 30 feet for fink truss at 6/12 pitch (the additional pitch increases the moment arm and allows longer spans). For 8/12 pitch fink: up to 32 feet. For 10/12 or 12/12 fink: up to 34-36 feet at the 2x4 size.
2x6 roof truss span chart: up to 36 feet for common truss; up to 40 feet for fink at 4/12; up to 44 feet at 6/12; up to 48 feet at 8/12. For 10/12 to 12/12: up to 50-52 feet. The 2x6 size is the residential workhorse for spans over 32 feet.
2x8+ roof truss span chart: 50+ feet for fink at any standard pitch. Beyond 60 feet, the truss design typically requires custom engineering with deeper top chords or alternate profiles. 2x10 and 2x12 top chords appear in agricultural and light commercial applications more than residential.
Bottom chord sizing follows similar logic: 2x4 bottom chords for spans under 30 feet, 2x6 for 30-40 feet, 2x8+ for longer spans. The bottom chord must support the ceiling load (drywall, insulation, attic storage if any) plus its own self-weight, with deflection limits typically L/240.
For high snow loads (over 50 psf, common in mountain regions and Northern climates) all of the above spans drop by 15-30%. Verify the snow load with your local building department before assuming the standard table values apply.
Specific truss dimensions: 30 foot 4/12 and other common cases
Builders frequently search for specific truss dimensions when planning a project. The most common queries: 30 foot 4/12 truss dimensions, 4/12 pitch truss dimensions, 30 ft truss 4/12 pitch (also written 30 ft truss 4 12 pitch in some search forms).
30 foot 4/12 truss dimensions: the peak height above the bottom chord = (30/2) × (4/12) = 5 feet. Total truss height (including 3.5-inch top chord and 3.5-inch bottom chord depths) = approximately 5 feet 7 inches from bottom of bottom chord to top of top chord at the peak. Top chord length (the rafter member) = sqrt((15)² + (5)²) = sqrt(250) = 15.81 feet, plus 1-2 feet for the heel detail at the wall plate. Bottom chord length = 30 feet (matching the span).
30 foot 6/12 truss dimensions: peak height = (30/2) × (6/12) = 7.5 feet. Total truss height ≈ 8 feet at peak. Top chord length = sqrt(225 + 56.25) = 16.77 feet plus heel allowance. Steeper than 4/12, with more material per truss.
30 foot 8/12 truss dimensions: peak height = (30/2) × (8/12) = 10 feet. Total truss height ≈ 10.6 feet at peak. Top chord length = sqrt(225 + 100) = 18.03 feet plus heel allowance.
24 foot 6/12 truss dimensions: peak height = (24/2) × (6/12) = 6 feet. Top chord length = sqrt(144 + 36) = 13.42 feet. Bottom chord = 24 feet. Smaller than the 30-foot equivalent — typical for a smaller addition or detached garage.
40 foot 6/12 truss dimensions: peak height = 10 feet. Top chord length = sqrt(400 + 100) = 22.36 feet plus heel allowance. The largest commonly-stocked residential truss size; spans up to 40 feet are typical for open-plan single-story homes.
4/12 pitch truss dimensions for various spans: peak height (in feet) = span/6. So a 24-foot 4/12: 4 feet. 30-foot 4/12: 5 feet. 36-foot 4/12: 6 feet. 40-foot 4/12: 6.67 feet. 4/12 pitch trusses are the lowest-profile commonly used in residential, popular for ranch-style and modern designs.
Pitch options and what they cost
Trusses can be ordered for any pitch from 2/12 (low slope) up through 18/12 (very steep). Most residential trusses are 4/12 to 8/12, with 6/12 being the most-ordered single pitch in the U.S.
Pitch determines truss height: for span S and pitch P/12, peak height = (S/2) × (P/12). A 30-foot truss at 6/12: peak height is 7.5 feet above the bottom chord. The same span at 12/12: 15 feet. Steeper pitches mean taller trusses, more material, and more shipping volume.
Cost grows roughly linearly with pitch. A 30-foot 4/12 truss costs about 10-15% less than the same 30-foot truss at 8/12, and 25-35% less than the same truss at 12/12. Beyond 12/12, costs accelerate because the assemblies require taller manufacturing jigs, more bracing during transport, and larger installation cranes.
For finished-attic designs, the practical sweet spot is 8/12 to 12/12 pitch. Below 8/12 the usable attic space is too narrow; above 12/12 the marginal usable area gains plateau but cost continues climbing.
Pitch also affects shipping. 30-foot trusses at 4/12 ship two to three per flatbed (vertical clearance is the limiter). 30-foot trusses at 12/12 ship one or two per flatbed because the trusses are much taller. Steeper pitches add 15-30% to shipping cost on top of the manufacturing premium.
On-center spacing
24-inch on-center is the U.S. residential default for trusses. Most prescriptive design tables and engineered truss specifications use 24-inch on-center as the baseline. 16-inch on-center is allowed and sometimes specified for high-load conditions or longer-span designs, but it doubles the truss count and project cost without meaningful benefit in most cases.
Compared to stick framing, 24-inch on-center trusses are structurally equivalent to or stronger than 16-inch on-center stick framing because the truss carries loads through both top and bottom chords plus the web pattern. The truss-on-truss spacing of 24 inches is one of the engineering advantages of truss construction.
For unusual conditions (very long spans, heavy snow loads, high-wind regions), the truss engineer may specify tighter spacing, larger lumber sizes, or both. Specific examples: in ASCE 7 wind exposure D zones (coastal areas), the engineer may specify 16-inch on-center to handle wind-uplift loads. In Region 7+ snow zones (mountain regions), 16-inch on-center plus 2x6 top chords is common.
Rafter truss design — when trusses replace rafters
Rafter truss design is the engineering decision to use trusses instead of conventional stick-built rafters. The decision is driven by cost, schedule, and structural performance.
Cost: trusses come out 10-20% cheaper than equivalent stick framing for most residential projects. The premium for engineered components (the trusses themselves cost more per board foot than dimension lumber) is offset by the much faster installation. A typical 1,800 sq ft house: stick-frame the entire roof in 3-5 days with a crew of 3; truss-frame the same roof in 1 day with a crew of 4 plus a crane operator.
Schedule: trusses arrive ready-to-install. The framing crew sets all trusses in a day, sheaths the roof the next day, and is ready for roofing material before the end of the week. Stick framing extends the dried-in milestone by 2-4 days.
Structural performance: engineered trusses have predictable structural performance verified by the truss design engineer. Stick-built rafters depend on the carpenter's craftsmanship and the inspector's verification. For typical residential conditions both work; for any unusual condition (long spans, complex roof shapes, high-wind regions, heavy snow), trusses are the safer choice because the engineered design provides documented capacity.
When stick framing wins: custom or unusual roof shapes that don't fit standard truss profiles. Renovations or additions where matching existing rafters is required. Buildings with restricted access where craning a truss into position is not possible. Designs requiring full-floor structural attic space (where attic trusses don't give enough usable area).
Truss cost in 2026
Pricing is per truss, per piece. A standard 30-foot 6/12 fink truss in 2026: $250-450 per truss in average U.S. markets. The price varies with lumber prices (which fluctuate), region, manufacturer, and current order backlog.
For a typical 1,500-2,500 sq ft house, plan on 25-40 trusses depending on building length and on-center spacing. Total truss cost: $7,000-15,000. Add 15-25% for engineering and stamping if not included.
Premium and specialty profiles cost more. Attic trusses run 40-60% above equivalent fink trusses. Scissor trusses run 25-35% more. Steeper pitches run 15-25% more. Engineered designs for unusual spans or loads add 20-40% to the standard pricing.
Lead times vary seasonally. In peak construction season (April-October), expect 4-8 weeks from order to delivery. Off-season (November-February), 2-4 weeks. Truss delivery is typically a single day for a residential project, with the trusses delivered on a flatbed and craned into place by the installer.
Specific truss size pricing examples: 24-foot 4/12 fink truss: $180-280 per truss. 30-foot 6/12 fink: $250-450. 36-foot 6/12 fink: $320-500. 40-foot 6/12 fink: $400-650. Pricing approximate; verify with local truss suppliers.
How we sourced these recommendations
Truss specifications and span values reflect typical 2026 industry practice for U.S. residential construction. Specific values vary by region, snow load zone, wind exposure, ceiling load, and manufacturer. The Truss Plate Institute (TPI 1-2014, "National Design Standard for Metal Plate Connected Wood Truss Construction") provides the underlying engineering standards. For project-specific design, verify with engineered truss calculations from your truss manufacturer.
Pricing figures reflect 2026 typical residential pricing in major U.S. metro markets. Pricing varies by region, manufacturer, current lumber prices, and order volume. Recommendations are reviewed annually and updated whenever industry pricing or design practices change materially. For any project requiring engineered design, defer to a licensed structural engineer or truss design professional familiar with your local conditions and code.
Need to run the numbers?Use the free roof pitch calculator on the home page to convert pitch to angle, calculate rafter length, or estimate roof area in any unit.