I- joist: sizes, span and cost per foot

I- joist: sizes, span and cost per foot

I-joists, also known as engineered wood joists, have become increasingly popular in modern construction due to their strength and versatility. These innovative beams, made of oriented strand board (OSB) and glued together in a unique shape, offer a number of advantages over traditional lumber joists. However, before incorporating I-joists into a building project, it is important to understand their various sizes, spans, and costs per foot to ensure proper and cost-effective use. In this article, we will discuss the different sizes and spans that I-joists are available in and how these factors influence the cost per foot, providing valuable insights for builders and contractors.

What is i joist ?

What is i joist ?

An I-joist, also known as engineered wood joist, is a structural component used in construction that is designed to provide support for floors, roofs, and walls. It is an innovative alternative to traditional solid wood joists and offers numerous advantages in terms of strength, stability, and cost efficiency.

An I-joist is made up of two flanges or top and bottom chords, which are connected by a web of oriented strand board (OSB) or plywood. The flanges are typically made of either laminated veneer lumber (LVL) or solid sawn timber, while the web is composed of OSB panels that are either glued or nailed to the flanges. The combination of these materials creates a lightweight and strong structure that can span longer distances without sagging or flexing.

One of the key advantages of using I-joists in construction is their high strength-to-weight ratio. Compared to traditional solid wood joists, I-joists have a higher load-carrying capacity, which means they can support heavier loads over longer spans. This makes them a popular choice for floor and roof construction in both residential and commercial buildings.

In addition, I-joists are more stable and less prone to warping, twisting, or shrinking than solid wood joists. This is because the web acts as a stabilizing element, preventing the flanges from moving and maintaining the shape of the joist over time. This stability is especially important in high-humidity or moisture-prone areas, where solid wood joists are more susceptible to damage.

The use of I-joists also allows for more efficient and cost-effective construction. As they come in standard sizes and lengths, they can be easily cut to fit on-site, reducing labor time and costs. Moreover, their lightweight nature makes them easier to handle and install, resulting in faster construction progress.

Another benefit of I-joists is their superior acoustic performance. The OSB web acts as a sound barrier, reducing sound transmission between floors. This makes I-joists a popular choice in multi-story buildings where sound proofing is crucial.

In conclusion, I-joists are a versatile and efficient structural component used in construction to provide strength, stability, and cost savings. Their unique design and material composition make them an ideal choice for a wide range of applications, making them an essential element in modern building design and construction.

Common i joist application

Common i joist application

Common I-joists, also known as engineered wood I-beams, are a popular construction material in the field of civil engineering. They offer many advantages over traditional wood joists, making them a preferred choice for many construction projects.

I-joists are made from oriented strand board (OSB) or laminated veneer lumber (LVL) flanges with a vertical oriented web of OSB or plywood in between. This biologically engineered construction material provides a high strength-to-weight ratio, making it ideal for use in areas that require long spans and heavy loads such as floor and roof systems.

One of the most common applications of I-joists is in residential construction. They are often used as floor joists and roof rafters in single-family homes, apartments, and other residential buildings. They offer a strong and sturdy base for the floors and roof, making them an essential component in the structural integrity of a building.

I-joists are also used in commercial and industrial construction, especially in large spaces like warehouses and factories. Due to their lightweight nature, they are easy to handle and install, making them a preferred choice in projects that require quick construction times. They also allow for larger spans, reducing the need for intermediate supports and creating more open spaces in the building.

Another significant application of I-joists is in the construction of multi-story buildings. In this case, they are used as floor joists, allowing for greater load-bearing capacity and longer spans without compromising the building’s structural integrity. They are also used in roof construction, providing a level surface for roof sheathing and simplifying the installation of mechanical systems, such as plumbing and electrical work.

In addition to standard applications, I-joists are also used in special structures, such as bridges and piers. They offer flexibility in design and can be customized to fit the specific load and span requirements of these structures.

Some other notable applications of I-joists include mezzanines, decks, and agricultural buildings. They are also used as a replacement for traditional wood beams in remodels and renovations, providing a stronger and more efficient structural solution.

In conclusion, the wide range of applications of I-joists make them a versatile and indispensable material in civil engineering. With their high strength, lightweight construction, and ease of installation, they have become a preferred choice for many construction projects, providing long-lasting and reliable structural support.

I joist sizes

I joist sizes

I-joists, also known as engineered wood joists or “I-beams”, are a popular choice for residential and commercial construction due to their strength, durability, and versatility. These joists are made of a combination of gluelam flanges and oriented strand board (OSB) webs, making them lighter and stronger than traditional solid wood joists.

The size of I-joists varies depending on the building requirements and spans. The most common sizes range from 2×4 inches to 2×14 inches. However, there are also larger sizes available for specific applications.

2×4 and 2×6 I-Joists are typically used in light framing applications such as roofs, floors, and walls. These sizes are suitable for shorter spans up to 20 feet and can support light loads. The 2×4 joist size is commonly used in residential construction, while 2×6 joists are more common in commercial buildings.

For longer spans and heavier loads, larger I-joist sizes are used. 2×10 and 2×12 I-joists can span up to 28 feet and are commonly used in long floor joists, roofs, and beams. These sizes are also popular for basements and garages where larger spans are required.

The largest I-joist sizes, 2×14 and 2×16, are used in heavy-duty applications such as commercial buildings, warehouses, and industrial structures. These joists can span up to 60 feet and can support heavy loads, making them suitable for large open spaces.

One of the significant advantages of using I-joists is that they can be manufactured to custom sizes and lengths to fit specific building requirements. This flexibility allows for efficient use of materials and can minimize waste on the job site.

It is essential to consult with a structural engineer or follow building codes to determine the appropriate I-joist sizes for a specific project. Considerations such as span, load, and spacing between joists must be taken into account to ensure the structural integrity of the building.

In conclusion, I-joists come in a wide range of sizes, from 2×4 to 2×16, to suit different building requirements. Their lightweight, strength, and customizability make them a popular choice for construction projects. However, it is crucial to work with a professional to determine the appropriate size and spacing of I-joists to ensure a safe and sturdy structure.

I joist common uses

I joist common uses

I joists, also known as engineered wood I beams, are increasingly becoming a popular choice in construction projects. These innovative structural members offer many advantages over traditional solid timber joists, making them a preferred option for civil engineers.

The most common use of I joists is in residential and commercial flooring systems. Their lightweight yet strong design allows for longer spans, reducing the need for additional support beams and columns. This makes them particularly useful in open floor plans and in areas where a large, uninterrupted space is desired.

I joists can also be used in roofing systems, providing a cost-effective alternative to traditional timber rafters. They are known for their dimensional stability, which reduces the risk of warping or twisting over time. This is especially important in roofing, where structural integrity is crucial.

Another common use for I joists is in wall framing. They can be used as studs, headers, or rim joists, providing a strong and efficient alternative to traditional lumber. Their consistent dimensions and predictable performance make them well-suited for framing walls and reducing construction time.

In addition to these uses, I joists are also commonly used in industrial and agricultural buildings, as they can span large distances without the need for intermediate support. They are also used in multi-story buildings, where their lightweight design can reduce the overall weight of the structure and allow for larger building heights.

One of the main advantages of I joists is their ability to accommodate mechanical and electrical systems within their open web design. This eliminates the need for drilling or notching, which can weaken traditional solid lumber joists. As a result, I joists are often used in buildings with complex mechanical or electrical systems, such as hospitals and office buildings.

In summary, I joists are highly versatile and can be used in a wide range of construction projects. Their strength, dimensional stability, and ability to accommodate service installations make them a practical and cost-effective choice for civil engineers. As technology continues to advance, it is likely that we will see even more innovative uses for I joists in the future.

I joist cost

I joist cost

I-joists, also known as engineered wood joists, are a popular type of structural support used in residential and commercial construction projects. They are designed to provide a cost-effective and efficient solution for floors, roofs, and other horizontal structural elements.

The cost of I-joists can vary depending on several factors such as the brand, size, and length of the joists, as well as the location and supplier. On average, the cost of I-joists ranges from $1.50 to $3.00 per linear foot.

One of the main reasons for the popularity of I-joists is their cost-effectiveness. They are considerably cheaper than traditional solid lumber beams as they use less material and can carry greater loads. This means that less labor is required for installation, resulting in lower overall costs.

Another factor that affects the cost of I-joists is the size and length. Longer joists will cost more than shorter ones, and wider joists will cost more than narrower ones. This is because longer and wider joists require more material and are able to carry heavier loads.

The brand of I-joist also plays a significant role in the cost. There are several reputable manufacturers of I-joists in the market, each with their own specific prices. Some leading brands include Weyerhaeuser, Boise Cascade, and LP Building Products.

The location of the project can also impact the cost of I-joists. In some areas, there may be a limited supply of I-joists, which can drive up the price due to transportation costs. It is recommended to source I-joists from local suppliers to minimize transportation costs.

In addition to the cost of the I-joists themselves, there may be additional expenses for hardware such as hangers and connectors, as well as labor costs for installation. It is important to factor in these additional costs when estimating the overall cost of using I-joists.

In conclusion, the cost of I-joists can vary depending on several factors such as brand, size, length, location, and additional expenses. However, they are generally a cost-effective option compared to traditional solid lumber beams, making them a popular choice among builders and contractors.

I- joist span

I- joist span

I-joists, also known as composite joists or engineered wood joists, are structural elements commonly used in construction for floor and roof framing. They are designed to provide a strong and lightweight alternative to traditional solid wood joists.

The span of an I-joist refers to the distance between the two supporting walls or beams that the joist is spanning across. It is a critical factor in the design and construction of any building, as it determines the load-bearing capacity and overall stability of the structure.

The span capabilities of I-joists vary depending on several factors such as the type of wood used, the joist depth, and the spacing between the joists. The most commonly used wood types for I-joists are softwood, such as spruce, pine, and fir, and hardwood, such as oak and maple.

The depth of an I-joist is an essential factor in determining its span capacity. As a general rule, the deeper the joist, the longer the span it can support. This is because a deeper joist has a larger moment of inertia, which is the measure of its resistance to bending. The moment of inertia is directly proportional to the square of the joist depth, meaning that a small increase in depth can result in a significant increase in span capacity.

The spacing between I-joists also affects its span capabilities. The closer the joists are spaced, the shorter the span can be, as they work together to distribute the load. The typical spacing for I-joists is between 12 to 24 inches on center, with 16 inches being the most common.

The American Wood Council (AWC) publishes span tables that provide guidelines for the maximum allowable spans for different types of I-joists based on their depth, wood type, and spacing. These tables are based on building codes and are used by engineers and architects in the design of a structure.

One of the significant benefits of using I-joists is their versatility in handling varying span lengths. They can be ordered in a wide range of lengths, allowing for flexible and more efficient structural designs. They can also be cut to size on-site, making them suitable for custom designs.

In conclusion, as a civil engineer, understanding the span capabilities of I-joists is crucial in the design and construction process. Properly selecting and spacing I-joists based on the specific requirements of a building ensures the structural integrity and safety of the structure.


In conclusion, I-joists offer several benefits compared to traditional solid lumber joists, such as enhanced strength, stability, and cost-effectiveness. The various sizes of I-joists available in the market make them suitable for a wide range of residential and commercial construction projects, providing designers and builders with flexibility in their designs. Additionally, the longer span capabilities of I-joists reduce the need for additional supports, saving time and labor during construction. Though the cost per foot may be slightly higher compared to solid lumber joists, the long-term cost savings and benefits make I-joists a wise investment. Ultimately, choosing I-joists for your next construction project can result in a durable, efficient, and cost-effective structure.


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