How to Compare Engineered I-Joists Without Guessing at the Structure

TJI floor joists are often discussed as if a series name or advertised maximum span were enough to choose a member. They are not. A defensible comparison begins with documented product geometry, then accounts for actual span, spacing, loads, supports, deflection criteria, floor assembly, service openings, installation details, local code, and current regional literature.

This article is a product-reference and selection-input guide. It can help readers prepare for a conversation with a supplier, designer, inspector, or structural professional, but it does not establish that a particular floor is structurally adequate or code compliant.

Mortar Desk publishes general building-material reference information, not project-specific engineering or contracting advice.

For more on that editorial boundary, see About Mortar Desk. Structural work should be completed by qualified trades or professionals working to the locally applicable code and approved project documents.

Editorial review: Mortar Desk. Technical sources and retail snapshots checked August 13, 2026. This was not a project-specific engineering review.

What TJI joists are—and what the name does not tell you

TJI is Weyerhaeuser’s brand name for a line of engineered wood I-joists. It should not be used as a generic specification for every engineered I-joist because other manufacturers’ products have their own design properties, installation rules, hole limits, and technical literature.

A TJI member has an I-shaped cross-section:

• A structural top flange
• A structural bottom flange
• A thinner web connecting the two flanges

Weyerhaeuser identifies residential and light-commercial floor and roof framing as product applications; building suppliers also describe TJI members as part of Weyerhaeuser’s engineered-wood framing family. Builders’ General summarizes those floor and roof applications.

Several specifications that are easy to conflate must be kept separate:

• Series identifies a product family, such as TJI 110 or TJI 560.
• Depth is the member’s overall vertical dimension.
• Flange width is the horizontal width across a flange.
• Web thickness is the thickness of the central panel.
• Ordered length is the physical length supplied for cutting or installation.
• Clear span is the unsupported distance measured between bearing faces.

Knowing that a joist is 14 inches deep does not identify its flange width, series, allowable span, or ordered length. Likewise, a supplier’s statement that a member is available in a long length does not mean the full length may be used as an unsupported span.

Weyerhaeuser promotes low weight, long available lengths, dimensional stability, easier installation, and space for approved service penetrations as practical benefits. These are manufacturer claims rather than independent performance findings. Dimensional consistency may reduce some variability associated with solid-sawn lumber, but it does not make a completed floor automatically squeak-free or bounce-free.

The central distinction is:

A product description tells you what the member is; a completed design determines what it may do in a particular building.

TJI series and dimensions at a glance

Weyerhaeuser lists six TJI series. It describes products from 9.5 through 16 inches deep as more widely stocked and says lengths may be available up to 60 feet, subject to product and regional availability. The table below was checked against the manufacturer’s product page on August 13, 2026. Verify the current Weyerhaeuser dimensions and availability before ordering.

This is a geometry reference, not a span chart or substitution table. Geometry alone does not establish allowable span, load capacity, stiffness, bearing requirements, hole permissions, or interchangeability. Two series offered at the same depth may have different design properties.

A wider flange or thicker web may be relevant to performance and detailing, but it cannot be converted into a safe span through a rule of thumb. Manufacturer dimensions should also take precedence when a retail title, product field, or nominal description is internally inconsistent.

Actual procurement can be constrained by:

• Distributor inventory
• Regional product mix
• Supplier cutting policies
• Requested cut increments
• Maximum delivery-vehicle length
• Jobsite access
• Handling and storage limits
• Minimum order quantities
• Lead time for nonstock products

Confirm the exact series, depth, flange width, web thickness, and supplied length rather than ordering by depth alone. Availability up to a stated maximum length is not a promise that every series and depth will be stocked locally in that length.

Why there is no single TJI span answer

There is no universal allowable span for TJI floor joists.

A statement such as “TJI joists span 20 feet” is incomplete unless it identifies the series, depth, spacing, loads, deflection criterion, support conditions, and other governing details. The same product can have different allowable spans under different design assumptions.

Clear span is measured face to face between supports, not from one physical end of the joist to the other. General joist-sizing guidance also emphasizes that both strength and stiffness require evaluation, although its dimensional-lumber examples cannot be used to size proprietary TJI products. See the American Wood Council span-table tutorial.

Before consulting a product table or design tool, assemble these inputs:

• Clear span: Face-to-face distance between the relevant supports
• On-center spacing: Distance between adjacent joist centerlines
• Live load: Load arising from use and occupancy
• Dead load: Weight of permanently installed materials
• Series and depth: Exact product under evaluation
• Deflection criterion: Applicable limit or project performance target
• Bearing conditions: Support type, bearing arrangement, and connections
• Support layout: Beams, bearing walls, hangers, and load path
• Concentrated loads: Tubs, islands, posts, masonry, equipment, heavy partitions, or similar loads
• Openings: Stairs, shafts, fireplaces, and interruptions in repetitive framing
• Cantilevers: Portions extending beyond a support
• Applicable code: Locally adopted edition and amendments
• Sensitive finishes: Tile, stone, brittle ceilings, or materials affected by movement
• Service requirements: Plumbing, ducts, wiring, and other planned penetrations

Both strength and stiffness must be checked. A joist might resist the calculated bending and shear demands yet deflect more than the governing limit. Conversely, passing one deflection check does not prove that bearings, connections, concentrated loads, openings, fire protection, or the rest of the floor system are acceptable.

Depth, series, spacing, and support layout can all change calculated performance. Greater depth may improve stiffness; another series may have different design properties; closer spacing can distribute uniform floor load among more members; and another support can shorten the span. These are variables to evaluate, not universal prescriptions.

Some reseller pages advertise TJI systems as capable of spans up to 32 feet. That is a conditional marketing claim, not an allowance for every TJI series, floor, or load combination. The same seller promotes project-specific layouts and multiple series and depths, illustrating why the headline figure cannot replace design inputs. Forest Products Supply presents the 32-foot figure as a maximum product capability.

Do not apply a dimensional-lumber span table or a generic online joist calculator to a proprietary TJI product. General tutorials can explain clear span, live load, dead load, strength, and deflection, but final TJI selection requires current regional manufacturer data or software and any project-specific engineering required by the plans or jurisdiction.

Strength, deflection and the floor that occupants actually feel

Floor performance involves three related but distinct questions:

1. Strength: Can the member resist the required structural forces?
2. Allowable deflection: Is calculated movement within the specified limit?
3. Vibration or perceived response: Does the completed floor feel acceptably firm to occupants?

Passing one question does not automatically answer the other two.

Deflection limits are commonly written as a ratio of clear span. At L/360, the calculated limit is the clear span, expressed in the same units, divided by 360. For a 10-foot clear span:

• 10 feet equals 120 inches.
• 120 ÷ 360 equals 0.333 inch.
• The resulting limit is approximately one-third inch.

An L/480 criterion permits less calculated deflection than L/360 over the same span and is therefore the stiffer criterion. Neither ratio is a universal requirement for every project. In the available seller material, L/480 is promoted as a floor-performance target rather than established as mandatory for all buildings.

Allowable deflection is not a complete vibration prediction. Variables that may be evaluated include:

• Joist depth and series
• Joist spacing
• Clear span
• Support placement
• Subfloor thickness and attachment
• Ceiling and partition interaction
• Concentrated loads
• Room use and floor layout
• Continuity and framing around openings

Weyerhaeuser also offers a proprietary TJ-Pro rating intended to address floor-performance expectations. It is an additional manufacturer tool, not a universally adopted code standard.

Practitioners debate how much weight to give minimum span-table compliance, stricter deflection targets, and proprietary performance ratings. One online discussion records users considering whether joists that passed a selected table check would deliver the desired subjective stiffness and whether depth, series, or spacing should change. Contributor qualifications and project inputs are not fully documented, so the discussion is anecdotal and should not be used as design guidance. Contractor Talk records those differing user opinions.

A practical decision has two stages. First, establish structural and code compliance. Second, determine whether the owner, designer, or builder wants a higher performance target for perceived stiffness or sensitive finishes. Any proposed change must still be recalculated rather than assumed to work.

Holes for plumbing, wiring and ducts: web only, within published limits

The governing rule comes first:

Field-cut penetrations may be made only in the web and only within the current manufacturer’s limits for their size and location. The top and bottom flanges must not be cut or notched.

Allowable openings can depend on:

• TJI series
• Joist depth
• Hole shape and dimensions
• Distance from bearings
• Spacing between openings
• Applied loads
• Nearby concentrated loads
• Cantilevers and framing openings
• Other project-specific design conditions

Ordinary field-cut holes are prohibited in designated zones near bearings. Pre-engineered knockouts may be permitted under the applicable instructions, but a knockout is not general permission to enlarge it or place another opening nearby. Consult Weyerhaeuser’s current product and allowable-hole guidance before cutting.

Generic hole diameters, rectangular-opening dimensions, and bearing-zone distances are intentionally not reproduced here. Those limits vary with the selected product and condition, and an oversimplified rule could put a cut where it is prohibited.

Coordinate framing and mechanical, electrical, and plumbing layouts before ordering, especially when:

• A large HVAC duct must cross several joists
• Multiple pipes need the same part of the floor
• Drain slope limits the available route
• A stair or shaft interrupts repetitive framing
• A concentrated load occupies the preferred service path
• Deep or less commonly stocked joists are being considered

If a hole is oversized, misplaced, too close to a bearing, or otherwise outside standard published conditions, stop work. Apply the same rule to any notched, drilled, split, or damaged flange. Do not add plywood, blocks, straps, screws, or other improvised reinforcement based on a generic repair found online. Obtain a condition-specific review from the manufacturer, project designer, or qualified structural professional.

Approved TJI web openings can accommodate many services, but they do not provide the same open pathways as an open-web floor truss. Open-web trusses are generally favored when extensive mechanical, electrical, plumbing, sanitary, or sprinkler distribution must pass through the floor depth.

Installation and construction-safety rules that purchasing guides often omit

TJI joists are unstable during erection until they have the required lateral restraint and temporary safety bracing. Install that bracing before workers or stored construction materials load the incomplete system.

Weyerhaeuser states that ordinary floor framing does not require bridging or mid-span blocking. That does not mean a TJI floor can be installed without lateral support, blocking, reinforcement, or special details anywhere. Required components can still occur at:

• End bearings
• Cantilevers
• Stair and floor openings
• Rim or edge conditions
• Load-bearing partitions
• Concentrated loads
• Hanger connections
• Other locations identified by the framing plan

Bearing dimensions, rim details, connector schedules, fastening patterns, web reinforcement, squash blocks, and cantilever assemblies must come from current plans and applicable manufacturer literature. Do not copy them from another project or infer them from a product photograph.

For roof framing, Weyerhaeuser requires a ridge beam or another form of vertical support at the high end. Roof applications also introduce their own loading, connection, ventilation, and fire considerations. A floor span selection cannot simply be transferred to a roof.

Fire protection is an assembly-and-code issue. A joist model alone does not establish a fire rating. Compliance can depend on the complete tested floor-ceiling or roof-ceiling assembly, including membranes, fasteners, insulation, penetrations, protection details, and the locally adopted code.

The manufacturer’s US document entry identifies TJ-4000 as the specifier’s guide for TJI 110, 210, 230, 360, and 560 joists. The landing page does not itself display the underlying installation tables, so download the current guide, record its revision date, and confirm that it applies to the selected product and region. Weyerhaeuser’s TJ-4000 entry was checked August 13, 2026.

Damage and unauthorized modifications requiring escalation include:

• Cut or notched flanges
• Split flanges
• Crushed or damaged webs
• Oversized or misplaced openings
• Unapproved rectangular cuts
• Altered bearing details
• Hanger or connector substitutions
• Water, impact, or handling damage of uncertain significance

Use this as a pre-concealment reminder, not as a substitute for the complete installation guide:

• Confirm the framing layout against member labels and delivery documents.
• Protect joists during unloading, handling, and storage.
• Install specified temporary bracing before loading the system.
• Use the approved hangers, connections, and bearing details.
• Keep both flanges intact.
• Check every web penetration against current guidance.
• Inspect members and service openings before concealment.
• Refer uncertain damage or nonstandard conditions for review.

Structural installation and damage evaluation should be handled by qualified trades or professionals working to the locally applicable code and approved project documents.

TJI joists versus dimensional lumber and open-web floor trusses

No floor-framing system is the automatic winner for every project. TJI joists, dimensional lumber, and open-web floor trusses solve different combinations of span, depth, service routing, handling, availability, and cost.

High-level comparison

TJI joists are promoted for low weight, long lengths, dimensional consistency, approved web penetrations, and potentially shallower assemblies. The tradeoff is dependence on product-specific design and installation rules.

Dimensional lumber is familiar to many builders and broadly stocked in many markets. Its span tables cannot be used to size TJI products.

Open-web floor trusses are generally favorable for routing HVAC, electrical, plumbing, sanitary, and sprinkler services. Comparative guidance also describes them as capable of longer spans in some designs, often with a deeper floor assembly. I-joists are characterized as easier to handle and install, but claims that every truss requires a crane or every TJI member can be carried safely by one person are too categorical. BASE4 summarizes the broad service-routing and floor-depth tradeoffs.

Why joist price is not the whole cost

The lowest floor-package quote may not produce the lowest installed building cost. The system can affect:

• Number and depth of framing members
• Freight and delivery equipment
• Installation labor
• Temporary bracing
• Interior supports and structural steel
• Wall and floor-to-floor heights
• Stair dimensions
• Exterior sheathing and finishes
• Insulation quantities
• Mechanical routing and soffits
• Fire-protection details
• Coordination and redesign time

Commercial comparisons argue that a shallower floor assembly can reduce costs elsewhere when floor depth changes stairs, walls, insulation, or exterior materials. That reasoning is project-specific and promotional, not proof that TJI joists always cost less. Builders Capital illustrates the broader cost categories in a project comparison.

Use a decision matrix rather than a product hierarchy:

The useful question is not “Which joist is best?” but “Which complete, approved floor system best fits this project’s constraints?”

Pricing, procurement and the documents to check before ordering

TJI pricing varies with series, depth, ordered length, quantity, supplier, region, freight, cutting policy, stock, and market conditions. A linear-foot figure is meaningful only when the underlying specification and quote terms are clear.

A Bay Area supplier published approximate estimates from about $4 to more than $8 per linear foot, depending on series and depth. No visible pricing-reference date accompanied those estimates, so they should be treated only as a regional benchmark. The page was checked August 13, 2026, not treated as a current national price range. Truitt & White explains the benchmark and its pricing variables.

Retail pages provide more specific but equally time-sensitive snapshots. On August 13, 2026, one listing displayed a 14-inch TJI 560 at $8.25 per linear foot, sold in 2-foot increments up to 48 feet, while warning that requested lengths were not guaranteed. Ring’s End displayed those purchase terms when checked.

Another page checked the same day displayed a 14-inch TJI 230 at $8.18 per linear foot. Its availability information was ambiguous because it showed both an out-of-stock message and a short availability window. It also contained an unexplained dimensional inconsistency, reinforcing the need to verify specifications against manufacturer literature. Dunn Lumber provided that retail snapshot.

Displayed prices, inventory, delivery coverage, requested lengths, and lead times can change. Before ordering, record:

• Exact TJI series
• Overall depth
• Flange width
• Web thickness
• Quantity
• Required supplied length
• Permitted cut increments or tolerances
• Framing-layout or plan reference
• Required hangers, rim products, and specified accessories
• Delivery address and access restrictions
• Unloading and storage arrangements
• Quote date and validity period
• Stock or special-order status
• Expected lead time

A quote should distinguish between requested length and guaranteed supplied length. Verify whether the supplier charges by ordered, supplied, or cut length and whether cutting fees, offcuts, minimum quantities, freight, or return restrictions apply.

Technical documents and tools

For US projects, TJ-4000 is identified as Weyerhaeuser’s specifier’s guide for TJI 110, 210, 230, 360, and 560 joists. The catalog landing page does not expose all technical tables, and its stated title does not include TJI 560D. Confirm the governing technical resource for the exact product rather than assuming that TJ-4000 covers every series.

Weyerhaeuser references TJ-4500 as a Canadian design resource. Use the guide applicable to the project’s region, and obtain it through the manufacturer’s current product-literature links. Do not assume that a US guide, Canadian guide, or older saved document remains applicable.

The manufacturer also identifies:

• ForteWEB, described as a free web-based structural design tool
• Javelin, another design and analysis resource
• TJ-Pro floor-performance evaluation
• Product installation and allowable-hole guidance
• Span, load, connection, and fire-protection information

Before purchase, obtain and record the revision or access date for the current:

• Installation guide
• Allowable-hole guidance or calculator
• Span and load information
• Approved framing layout
• Connection and accessory schedule
• Fire-assembly information, where applicable
• Regional design guide
• Warranty document

Weyerhaeuser advertises a limited lifetime product warranty, but that summary does not establish coverage, exclusions, eligibility, documentation requirements, or claims procedures. Review the actual warranty terms before relying on it.

A practical selection sequence is:

1. Measure the face-to-face clear span.
2. Establish joist spacing and all applicable loads.
3. Identify bearings, beams, walls, hangers, openings, cantilevers, and concentrated loads.
4. Record sensitive finishes and the desired deflection or floor-performance criteria.
5. Coordinate plumbing, wiring, and duct routes before selecting final members.
6. Compare the TJI series and depths actually available from local suppliers.
7. Verify the proposed design against current regional Weyerhaeuser literature and software.
8. Check the locally adopted code and obtain any required professional or jurisdictional approval.
9. Match the order to the approved framing layout rather than to a price or series name alone.

Price and series labels cannot replace a complete framing design. If a member is damaged, a service opening falls outside published limits, an unusual load is introduced, or a detail remains uncertain, stop and refer the condition to the manufacturer or a qualified structural professional before work continues.

Frequently asked questions

How far can TJI floor joists span?

There is no single allowable span. It depends on the exact series and depth, on-center spacing, clear span, live and dead loads, deflection criterion, bearings, supports, concentrated loads, openings, cantilevers, and applicable code.

Measure the clear span face to face between supports. Use current regional manufacturer tables or design software for the complete condition rather than relying on an advertised maximum.

Can holes be cut in TJI joists for plumbing, wiring or ductwork?

Yes, but field-cut holes may be made only in the web and within the current manufacturer’s limits for size, shape, location, and spacing. Top and bottom flanges must not be cut or notched.

An oversized, misplaced, or nonstandard hole—or any flange damage—requires a condition-specific review rather than an improvised repair. Coordinate service routes before ordering when large ducts or multiple utilities must cross the floor.

Do TJI floor joists require bridging or mid-span blocking?

Weyerhaeuser states that ordinary floor framing does not require bridging or mid-span blocking. Required lateral support and designed details may still be needed at end bearings, cantilevers, openings, rim conditions, concentrated loads, and other specified locations.

Temporary construction bracing is a separate safety requirement. TJI joists are unstable until properly laterally supported and must not be loaded prematurely.

Can TJI joists be used for roof framing?

Yes. TJI joists are identified for floor and roof framing, but roof use has its own loads, supports, connections, and installation requirements. The manufacturer calls for a ridge beam or another form of vertical support at the high end.

Do not apply a floor selection directly to a roof. Use current roof-framing guidance and the approved project design.

How much do TJI joists cost per linear foot?

There is no stable national price. Cost varies by series, depth, length, quantity, supplier, location, freight, cutting policy, inventory, and market conditions.

Supplier ranges and retailer listings are regional, time-sensitive snapshots. Obtain a dated local quote for the exact series, depth, quantity, and required lengths, then compare the complete installed system cost rather than joist price alone.