Truss Joist Span Chart: TJI, LPI, and Engineered I-Joist Span Tables

How engineered I-joists work

An engineered I-joist (also called a TJI, wood I-joist, or wood I-beam in residential framing) is an I-shaped structural member made of three engineered components: a top flange of laminated veneer lumber (LVL) or solid sawn lumber, a bottom flange of similar material, and an OSB (oriented strand board) web that connects them. The cross-section is shaped like a capital "I" — hence the name.

The I-shape is structurally efficient because bending loads in a beam concentrate at the top (compression) and bottom (tension), with relatively little stress in the middle. The flanges (top and bottom) take the bending load; the thin web in the middle just keeps the flanges separated. Compared to solid lumber, which has material throughout the cross-section, an I-joist achieves the same bending capacity with significantly less material weight and cost.

I-joist depth is measured from the top of the upper flange to the bottom of the lower flange. Standard residential depths: 9.5 inches (matches a 2x10 in floor framing), 11.875 inches (matches a 2x12), 14 inches (the next size up), 16 inches (used for long spans or heavy roof loads). Larger depths up to 24 inches are available for specialty applications (commercial, custom residential, long-span).

I-joist flange width: typically 1.75 to 3.5 inches, depending on the product and load capacity. Wider flanges = higher load capacity = longer span. Manufacturers offer multiple "performance levels" within each depth — for example, TJI 110, TJI 210, TJI 230, TJI 360, and TJI 560 series in increasing capacity (the higher the number, the wider the flanges and the longer the span).

The OSB web of an I-joist is critical to performance. Most I-joists allow holes through the web for plumbing, HVAC, and electrical (within manufacturer-specified zones marked on the joist), with the holes typically up to 1.5-3 inches diameter without needing reinforcement. Larger holes or holes outside allowed zones require web stiffeners (additional reinforcement strips). The web joist span table for each manufacturer shows allowable spans both with and without web stiffeners.

Truss joist span tables by depth

A truss joist span chart for residential floor framing under typical 40 psf live load + 10 psf dead load conditions, at 16-inch on-center spacing. Values are approximate for mid-grade I-joist series (TJI 210, LPI 20Plus, BCI 6000); always verify against the specific manufacturer's chart for your product.

9.5-inch I-joist: residential floor span 16-18 feet at 16" OC (16-foot for entry-level series, 18-foot for premium series). Compares to 2x10 dimension lumber at 15'9" — small advantage. The 9.5-inch depth is the most common entry-level I-joist size, used widely in tract-home construction since the late 1990s.

11.875-inch I-joist: residential floor span 19-22 feet at 16" OC. Compares to 2x12 dimension lumber at 19'2" — modest advantage. The 11.875-inch is the most common residential second-floor I-joist size — covers most modern open-plan rooms with comfortable margin.

14-inch I-joist: residential floor span 23-26 feet at 16" OC. No dimension lumber equivalent — the I-joist enables spans not achievable with solid lumber. Used for longer floor spans, large bonus rooms, and great rooms in luxury residential. Also used for heavily-loaded roof rafters in deep-snow zones.

16-inch I-joist: residential floor span 27-30 feet at 16" OC. Used for great rooms, open floor plans, and commercial-residential applications. The largest depth commonly used in residential construction; larger depths exist but are typically commercial.

Spacing variations: at 12-inch on-center (heavier-load applications), the same depth I-joist spans about 5-10% longer. At 19.2-inch on-center (less common but standard for some I-joist applications), spans about 5% shorter. At 24-inch on-center (light-load applications), spans about 10-15% shorter. The truss joist span tables in manufacturer documentation include all four standard spacings.

Roof rafter applications: I-joists used as roof rafters typically span 5-10% shorter than equivalent floor joists at the same depth, due to the additional dead load (roofing material) and seismic considerations. A 14-inch I-joist as a rafter at 24" OC: about 22-24 feet at typical roof loads. Verify against the manufacturer's rafter span tables (separate from floor span tables).

TJI span calculator — using a manufacturer-specific tool

A TJI span calculator is a manufacturer-specific tool from Trus Joist (Weyerhaeuser) that computes allowable spans for their specific TJI product line. Similar tools exist for other manufacturers — LPI by Louisiana-Pacific, BCI by Boise Cascade. Each tool runs the same fundamental engineering math but uses the specific load values and capacities of that manufacturer's product line.

Trus Joist iLevel Cut and Span calculator: free online tool from Weyerhaeuser, available at the Trus Joist website. Inputs: I-joist series (TJI 110, 210, 230, 360, 560), depth, spacing, span, load, and end-use (floor, roof, ceiling). Returns: pass/fail, suggested alternatives, and a printable design summary. The most commonly used calculator for the dominant TJI product line.

Why a manufacturer-specific calculator: the I-joist span tables vary slightly between manufacturers because each tunes their product to slightly different load capacities. A 9.5-inch TJI 210 spans about 17'6" at 16" OC; a 9.5-inch LPI 20Plus spans about 17'9" at the same conditions. The differences are small (1-3% typical) but matter for marginal cases. Use the calculator for the actual product you're specifying.

For preliminary design and rough sizing, the truss joist span chart values in this guide work fine. For final design before ordering material, run the manufacturer's calculator on the actual product you intend to use. The calculator is also useful for verifying compliance with bearing and concentrated-load requirements that don't fit a simple chart lookup.

For projects without a specific manufacturer chosen yet, use the most conservative product-line values across the major brands. The variance between brands is small; designing to the conservative values gives flexibility to switch brands during procurement.

Web stiffeners and bearing requirements

Web joist span table values typically have two columns: spans without web stiffeners and spans with web stiffeners. Web stiffeners are short reinforcement pieces (typically OSB or plywood) attached to the web at locations of concentrated load — bearing points, point loads, and openings. The stiffeners prevent the thin web from buckling under high local loads.

When web stiffeners are required: at bearing points where the joist sits on a wall plate or beam (the load is concentrated at the bearing area); at point loads where heavy items rest on a single joist (typically over 1,000 lbs concentrated); at openings cut for plumbing or HVAC where the cut weakens the web. The manufacturer's installation guide specifies exactly where stiffeners are needed for each product.

Stiffener material: typically 7/16-inch or 23/32-inch OSB or plywood, cut to fill the space between flanges and attached with nails or screws to the web. Some manufacturers offer pre-cut stiffener kits matched to their products; others require field-cutting from sheet material. Cost: $5-10 per stiffener pair; typical residential project needs 20-40 pairs at concentrated load points.

Bearing length: I-joists typically require minimum 1.75 inches of bearing on a wall plate or 3.5 inches on a beam (verify against the specific product). Less bearing reduces the allowable load and may require additional reinforcement. The bearing requirement is independent of the span — even a short joist needs full bearing at each end.

Concentrated loads: any point load over 500 lbs concentrated on a single I-joist requires special design consideration. Common concentrated loads in residential framing: bathtubs (especially Jacuzzi tubs at 800-1,200 lbs filled), water softeners, water heaters, HVAC equipment, large refrigerators with ice makers. The manufacturer's installation guide specifies how to reinforce around these loads — typically with additional joists, doubling, or a small structural beam.

Holes in the web: most I-joists allow circular holes up to 1.5-3 inches diameter through the web within a marked allowed zone. Larger holes or holes outside the zone require structural review or reinforcement. Plumbing, HVAC, and electrical contractors should coordinate with the structural design before cutting holes — some shapes (rectangular, large circular) compromise the web significantly.

Engineered I-joists vs. dimension lumber — when to choose each

The choice between engineered I-joists and dimension lumber depends on span, cost, and installation factors. Both work for many applications; the right choice varies by project.

Use I-joists when: the span exceeds dimension lumber capacity (over 19 feet for floor joists, where 2x12 maxes out); you need a flat ceiling surface (I-joists are straighter than rough-sawn dimension lumber, important for finish work); you need to drill holes for plumbing or HVAC (manufacturer-allowed in I-joist webs, restricted in dimension lumber); you need lighter material for handling (I-joists are 30-40% lighter than equivalent dimension lumber). For dimension-lumber sizing of standard floor joists or rafters, the floor joist calculator and rafter length calculator on this site run the IRC R502 and R802 math with full species and grade options.

Use dimension lumber when: the span is short enough that 2x10 or 2x12 covers it (most residential first-floor framing, deck joists); cost is the primary driver (dimension lumber is 30-50% cheaper than equivalent I-joists); the building is in a region where dimension lumber is locally cheaper than imported I-joists (rural areas in lumber-producing regions); the project is small and material handling is the bottleneck (a single 2x12 is easier to handle than an equivalent I-joist for one-person installation).

Cost comparison: a 9.5-inch TJI 210 I-joist runs $5-8 per linear foot vs. a 2x10 SPF #2 at $2-4 per linear foot — about 2-3× the cost. An 11.875-inch I-joist runs $7-12 per lf vs. 2x12 at $3-5 per lf. The cost premium is significant for small projects where dimension lumber covers the span.

For typical residential first-floor framing (10-15 foot floor spans): dimension lumber is usually the right answer. The cost advantage is meaningful and 2x10 or 2x12 covers the span easily. For second-floor framing (often 14-18 foot spans): I-joists become competitive due to span requirements. For long-span applications (great rooms, open plans, 20+ feet): I-joists are essentially required.

A truss joist (engineered I-joist) is also commonly used in roof rafter applications for cathedral ceilings, where the long unsupported run from eave to ridge benefits from the I-joist's longer-span capability. The same depth-for-depth advantage applies, with the additional benefit of straight rafter lines for cathedral-ceiling finishes.

I-joist manufacturers and product lines

Several major manufacturers compete in the residential I-joist market. The product lines are similar in design philosophy but differ in detail — flange material, web thickness, capacity ratings, and pricing. The following are the most common in U.S. residential construction.

TJI (Trus Joist) by Weyerhaeuser: the original I-joist product, dominant in U.S. residential framing since the 1980s. Series: TJI 110, 210, 230, 360, 560 (in increasing capacity). The 210 series is the most common residential floor joist; 230 and 360 are used for longer spans and heavier loads. Trus Joist also pioneered the iLevel computer-aided design system, which most contractors use for residential I-joist design.

LPI by Louisiana-Pacific: product line includes LPI 20Plus, LPI 23Plus, LPI 32Plus, LPI 36Plus, LPI 56 (in increasing capacity). LPI products are functionally similar to TJI at slightly different price points. Common in the western U.S. and Canada where LP has manufacturing presence.

BCI by Boise Cascade: product line includes BCI 5000, 6000, 6500, 8000, 9000. BCI products are also functionally similar to TJI. Common in the eastern U.S. where Boise Cascade has manufacturing presence.

RFPI by Redbuilt (formerly RFP Roseburg Forest Products): product line includes RFPI 20, 30, 36 series. Smaller market share than the big three, but available regionally. For projects also using engineered beams (rather than just I-joists), the same manufacturers typically offer LVL beam products in matching depths — the LVL beam calculator on this site covers sizing for that companion product.

Pricing across manufacturers: typically ±10% for equivalent products. The choice between brands often comes down to local availability, contractor familiarity, and supply yard stock. A roofing or framing contractor in a given region typically has a preferred brand based on supplier relationships and design tool familiarity.

For mixed-brand projects (some TJI, some LPI), match the depth and capacity rating but verify with the structural engineer or building inspector that the design accommodates the mix. Mixing brands within a single floor system is uncommon but allowed; mixing within a single load path (joists feeding into a beam) requires careful coordination.

Installation considerations for I-joists

I-joists are not interchangeable with dimension lumber for handling, storage, and installation. Several specific cautions apply that don't come up with solid lumber.

Storage: I-joists must be stored with the OSB web protected from moisture. Wet OSB swells and loses strength; long-term storage requires the joists either kept dry indoors or covered with tarps that allow ventilation. Don't store I-joists directly on the ground.

Cutting: do not cut, notch, or drill outside manufacturer-specified zones. The web has structural function; cutting it weakens the joist. Some products allow field-cutting the flanges to length (the flanges are dimension lumber); others require cuts made in factory with proper end seals. Verify before cutting.

Bracing: I-joists require temporary bracing during installation to prevent them from rotating or twisting under construction loads. The OSB web is thin enough that an unbraced I-joist can rack sideways under workers walking on it. Permanent ceiling drywall or subfloor sheathing provides final lateral support; temporary 1×4 strapping is required between installation and finish surfaces.

End conditions: I-joists require specific end blocking and rim joist treatment. The most common is a rim joist or end blocking made from OSB or plywood (sometimes called the "rim board") that closes the joist ends and transfers floor edge loads to the wall plate. The manufacturer specifies the rim board thickness and connection details.

Fire performance: I-joists are more vulnerable to fire than dimension lumber because the thin OSB web burns through faster than solid wood. Fire codes (especially in multi-family construction) often require I-joists to be wrapped with gypsum board or installed with sprinklers below to extend fire resistance. For single-family residential, basic OSB-web I-joists are accepted; check local code for any sprinkler or fire-protection requirements.

How we sourced these spans

Span values reflect typical published manufacturer span tables for residential applications under standard load conditions (40 psf live + 10 psf dead for floors, 30 psf snow + 10 psf dead for roofs). Specific values vary slightly by manufacturer and product series; always verify against the specific manufacturer's span tables for your project before locking in a design.

Cost figures reflect 2026 typical residential pricing in major U.S. metro markets. Pricing varies by region (West Coast and Northeast typically run 25% higher than national averages), distributor relationships, and project size. Recommendations are reviewed annually and updated whenever industry pricing or product specifications change materially. For project-specific design, defer to a licensed structural engineer or architect using the actual manufacturer's design tools.

For related framing reference, this site has dedicated tools across the full house picture. The LVL beam calculator covers laminated veneer lumber sizing for headers and beams. The 4x6 span table covers solid-sawn beam spans for traditional framing. The floor joist calculator handles dimension-lumber floor joists with IRC R502 compliance. The rafter length calculator and rafter sizing reference cover roof framing. The cost to build a house calculator covers full-project budgeting around the framing line items.