When designing or building floors or roofs we tend to think of dimensional lumber like 2x8s, 10s, and 12s depending on loads, spans, and spacing. The further the span, the greater the flex or bounce potential, or the need for more support beams. Why not consider TJI® joists?
TJI® joists are engineered joists that resist twisting, shrinkage, and warping, so there’s less chance of a squeaky, bouncy floor. They are lighter than dimensional lumber, provide greater strength and lengths, and thus longer spans, which can reduce some costs and better meet design requirements.
In this article, we’ll explain what TJI joists are, how they are used, their different sizes and span distances. We’ll also compare TJI joists with I-Joists, LVL, 2x12s, and TGI, look at where they can be purchased, and what they cost. Our goal is to provide you with the information you need to meet the design requirements of your project.
Contents (Jump to Topic)
What Does TJI Joist Stand For?
TJI joists are trademarked to Trus Joist, which is currently a Weyerhaeuser business. Trus Joist ‘invented’ the engineered wood I-joist and held the patent until recently. TJI stands for Truss Joist I-Joist.
The engineered wood I-joist can be used for joists or trusses, are stronger and lighter than dimensional lumber of similar widths, and can span greater distances. The truss-joists are engineered to resist twisting and warping, and won’t shrink like dimensional lumber. Plus, they use about 50% less wood than standard joists.
What Are TJI Joists Used For?
TJI joists are used for interior floor joists, trusses, and headers to provide larger open spaces or rooms. They can span further than dimensional lumber of similar sizing, so bearing points can be further apart. The greater span also means supports like beams, posts and footings may not be necessary, or fewer may be required, making for quicker installation and generating construction and environmental savings too.
TJI floor trusses are built with openings or can be cut or drilled to allow plumbing, electrical, and HVAC to pass through too, which means fewer obstructions below the joists or the need for bulkheads. Additionally, blocking and bridging isn’t typically required with TJI joists since the subfloor sheathing prevents rotation, which opens up the channel between joists for services too. This further reduces construction costs, build time, and the need for services to be suspended below the joists.
The joists can be used as ceiling joists too, but are designed to have sheathing applied to the top rail, so require bracing or strapping at the top for stability if left unsheathed. TJI joists are often used in residential and commercial construction projects. Additionally, since TJI joists are engineered to resist bowing, twisting, shrinkage, or warping, there is no time or money wasted culling unusable planks during the build.
Note: TJI Joists are for dry-use locations and should be protected from moisture.
TJI Joist Sizes
TJI joists are available in different widths and depths depending on the design properties and product number. Trus Joist Engineered Wood Products guide identifies their products as TJI 110, 210, 230, 360, and 560 in some regions, and as TJI s31, s33, and s47 in other regions.
How Far Can TJI Floor Joists Span?
The distance a TJI joist can span, like any joist, depends on the spacing between joists, live and dead load requirements, the ratio of deflection to length (L/x), sheathing thickness, ceiling applied or not, simple or continuous span, and other design factors.
Depending on various design factors and which TJI joist is used, the span can vary from 13’-7” for a TJI110 at 24” centers to 36’-1” for a TJI560 at 12” centers. When determining span, refer to the manufacturer’s specifications, the local building code, or the calculations of a Structural Engineer.
TJI vs I-Joist
Trus Joist, a Weyerhaeuser Business, created the engineered I-joist nearly 50 years ago and held the patent until recently. Engineered I-joists are essentially the same as the TJI joist, just not the original manufacturer. They are used the same as TJI joist, have a finger-jointed upper and lower flange, and the web is either plywood (LVL) or OSB, similar to the TJI manufacturing.
Both products have a top and bottom flange made of wood, however, TJI uses solid sawn lumber or finger-jointed wood while I-joists typically use LVL (laminated veneer lumber) or solid lumber. Separating and supporting the two flanges is a strip of plywood (LVL) or OSB oriented perpendicular between the flanges.
The wider and thicker the strip, the greater the span potential. TJI and I-joists both are lighter than solid wood members and resist shrinkage, twisting, bowing, and warping, can span further than dimensional lumber, plus they reduce squeaky or bouncy floors.
TJI joists commonly have rounded cutouts or pre-scored knockouts, while many I-joist manufacturers leave it to the builder to follow the manufacturer’s instructions and cut them out where required. TJI flange widths range from 1-3/4” to 3-1/2” and I-joists from 1-1/2” to 3-1/2”. The depths are also similar, except TJI offers 18” and 20” which isn’t typically available in other I-joists.
TJI vs LVL
TJI joists have a top and bottom flange made of solid or finger-jointed wood with a perpendicular sheet of OSB or plywood (LVL) in between. LVL (laminated veneer lumber) looks more like a plank except it’s made up of layers of thin veneer glued, heated, and pressed together, like plywood but much thicker. The span and strength are determined by the width and depth of both products, with TJI spanning up to 36’-1” and LVL typically 44’ but can be manufactured to span up to 60’.
TJI joists range from 1-3/4” to 3-1/2” wide, and come in depths of 9-1/2” to 20”, while LVL range from 1-1/2” to 7” wide and from 1-1/2” to 24” deep, depending on the manufacturer. LVL can also be built up on-site to make a wider, solid support structure using thinner and lighter individual components. Both products resist shrinking, warping, twisting, bowing, and splitting, making them more reliable and predictable than dimensional lumber.
Both LVL and TJI are used for trusses, joists, and headers. However, LVL can also be used as beams, posts, rim joists, hip and valley rafters, and even stair stringers. Additionally, both products typically are interior use only, but LVL manufacturers also offer different preservative treatments which allow it to be used in exterior applications too.
TJI vs 2×12
Design, span, and structural aspects typically affect lumber choice; however, cost, availability, and quality also affect it too. The increasing cost of 2x12s, their quality, and availability are helping to increase the demand for engineered joists. Old-growth trees produce the best 2x12s, making quality and availability a concern as there are fewer available and those that are, are being protected from harvesting.
TJI joists rely on thinner dimensional lumber for the top and bottom flange, and lengths are augmented by the use of finger jointed pieces for straighter and longer spans. Additionally, the web of the ‘I’ between the flanges is made of OSB or plywood (laminated veneer lumber or LVL), which makes use of wood residue or smaller dimension timber, including new growth forests. TJI joists also use up to 50% less ‘wood’ than is found in a 2×12 of similar length, making it lighter, more cost-efficient, and environmentally friendly in some ways.
A 2×12 is nominally 1-1/2” wide by 11-1/4” deep and can span up to 25’-7” if it’s structurally select (SS) Douglas Fir spaced at 12” centers, and has a moisture content around 15%, while other grades and species span shorter distances. However, the span of a 2×12 depends on load and deflection values, wood species, grade, spacing between joists, and moisture content.
Additionally, the timber is subject to shrinkage, twisting, warping, bowing, and defects. Plus, the depth of a 2×12 can vary from one to another, requiring planing down or shimming to level floors. A typical 2×12 is also heavy, weighing approximately 4.10 lbs/ft.
A TJI-110 joist is dimensionally closest in size to a 2×12, being 1-3/4” wide and 11-7/8” deep, but weighs only 2.5 lbs/ft. Its span is dependent upon loads, deflection, and spacing between joists, with its maximum span being 22’-3”, although a TJI 210, 230, and 560 of equal depth will span further.
TJIs of greater depths will span further too, with an 18” deep TJI560 spanning up to 36’-1”. However, all TJI joists are manufactured to be uniform in size, straight, and to resist twisting, shrinkage, bowing, warping, and are free of defects, regardless of wood species or grade used, so there’s no culling of unusable pieces and no worries of sagging or having to replace them later on.
TJI joists also have cutouts, perforated knockouts, or can be cut or drilled for electrical, plumbing, and HVAC which won’t compromise the structural strength. 2x12s can be drilling for electrical or small diameter plumbing feeds, but notching or drilling out holes for HVAC or larger diameter plumbing does affect the strength and can reduce span.
TJI joists typically don’t require blocking or bridging, which opens up the channel between joists for services too. 2x12s commonly require blocking, which means some services must run under the joists, resulting in bulkheads and loss of headroom.
Framing with 2x12s often requires footings, support posts, and beams to carry shorter pieces since availability and price usually result in a selection that won’t span the required distance. Using TJI 110 joists which will all span the same distance, or using joists with greater depth will result in greater spans and less need for intermediate supports. The result is larger openings and rooms without post or beam obstructions.
TGI vs TJI
TJI is a brand name for engineered I-joists owned by Weyerhaeuser but was initially owned by Trus Joist, the innovator of engineered I-joists for almost 50 years ago. The TJ stands for Trus Joist, and the I for I-joist, thus TJI joists.
Other forestry companies have since developed their own I-joists and acronyms, such Boise Cascade’s BCI joists, BLI joists by BlueLinx Products, and Louisiana Pacific’s LPIs. TGI, however, doesn’t exist as a product. It is most likely a mispronounced ‘J’, a common mistake, so TGI is actually TJI, not a different product.
Where to Buy TJI Joists?
Purchasing TJI joists isn’t quite as easy as 2x12s where all you do is walk into your local lumber yard. While there are hundreds of locations across the United States and Canada that carry TJI joists, most will need to order them in. Due to the wide array of lengths, widths, and depths available, most locations don’t have the space. However, that usually gives you exactly what you want and need in regards to your build. Additionally, in some instances, it can also place cutouts or perforated knockouts where needed too.
The easiest way is to contact your local lumber yards and ask if they are a distributor. Alternatively, check out this link Where to Buy : Weyerhaeuser, enter your ZIP code or scroll down to the map and navigate it to your region. If you don’t find a distributor close to you, ask your local lumber yard anyways, they may be linked with one that is, or be able to get what you want.
TJI Joists Cost
The cost of a TJI joist depends on its length, depth, width, how many your need, and distance from the nearest supply point to your build site. Lumber is a trading commodity, so the prices fluctuate from day to day and region to region, making pricing difficult.
The cost factor should also look at construction costs. Remember, when buying dimensional lumber, the price varies with species and grade, as does the span, which isn’t an issue with TJI joists.
TJI joists are uniform in dimensions whereas dimensional lumber can vary in thickness by as much as a 1/4 inch, requiring shimming or planing down. Using TJI joists at 16” centers to span the same distance as dimensional lumber at 12” centers generates savings too. Plus, TJI joists typically don’t require intermediate support beams, posts, and footings, making for larger spaces or openings, which also saves on material and labor costs.
Most lumber yards carry #2 grade 2×12 lumber for joists, which is $2.62 a linear foot at my local Box store presently. An equivalent 11-7/8” TJI-110 is about $3.20 per linear foot, while an 18” TJI s47 is about $5.10 a linear foot. However, opting for an 11-7/8” deep TJI 210, 230, or 560 will increase the span and keep the price reasonably competitive.
Expect to pay between 20% and 40% more per joist over comparable dimensional lumber, but if you need fewer and don’t require beams, support posts, and footings, the real cost in the build may equate to overall savings.
TJI joists are the original engineered lumber I-joist, and are a brand of I-joists owned and manufactured by Weyerhaeuser. They resist shrinkage, twisting, bowing, and warping, are uniform in shape, use up to 50% less wood than dimensional lumber, and are thus lighter and easier to place.
The uniformity in shape reduces squeaks and bounce and negates the need to shim or plane joists down. Although 20% to 40% more expensive than traditional lumber choices, they can generate significant savings by spanning further and requiring less structural buildup and labor.
Hopefully, you have a better understanding of what TJI joists are and how they can be used to improve your project’s design and build.