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The 2 by 4 is the most commonly used piece of wood in the world, but its dimensions are not what the name suggests. In fact, a 2 by 4 actually measures 1.5 by 3.5 inches.
This discrepancy can be traced back to the late 1800s when most dimensional lumber in the United States was produced by local manufacturers and only sold to customers in the vicinity of the mill.
The mills produced rough lumber which was not uniform in width nor had standard dimensions. Builders were accustomed to manually plane the boards on site and make them fit the project.
As the forests near the larger cities were depleted, lumber had to be shipped greater distances. At this point in time, railroad shipping was still extremely expensive, often double as expensive as the lumber itself.
Manufacturers figured out that instead of shipping rough lumber which is then planed at the construction site resulting in tons of wasted material, they could instead provide the surfacing at the mill before shipping and in that way reduce the weight of the shipment.
The opening of the Panama Canal in 1914 further complicated things. This new and considerably shorter shipping route made it possible for mills on the west coast to compete for the east coast markets. Since ocean rates are based on volume, the wood manufacturers had an even greater incentive to start shaving off any volume they could.
Key Takeaways
- The dimensions of a 2 by 4 are not actually 2 inches by 4 inches, but rather 1.5 inches by 3.5 inches.
- The standardization of the 2 by 4 was a result of the need for nationwide standardization and the desire to reduce shipping costs.
- The current size of a 2 by 4 is well-suited for light-frame construction, roofing joists, and other smaller projects.
Origins of the 2 by 4
The 2 by 4 is the most common piece of wood in the world, but its dimensions are actually 1.5 by 3.5 inches. This can seem misleading, especially to people outside of North America. However, the reason for this goes back over a century ago when most dimensional lumber in the United States was produced by local manufacturers and only sold to customers in the vicinity of the mill.
Before the late 1800s, the mills produced rough lumber which was not uniform in width nor had standard dimensions. Builders were accustomed to manually plane the boards on site and make them fit the project. However, when the forests near the larger cities were depleted, lumber had to be shipped greater distances. At this point in time, railroad shipping was still extremely expensive, often double as expensive as the lumber itself, so the manufacturers had to get creative.
They figured out that instead of shipping rough lumber which is then planed at the construction site resulting in tons of wasted material, they could instead provide the surfacing at the mill before shipping and in that way reduce the weight of the shipment. The opening of the Panama Canal in 1914 further complicated things. This new and considerably shorter shipping route made it possible for mills on the west cost to compete for the east coast markets. Since ocean rates are based on volume, the wood manufacturers had an even greater incentive to start shaving off any volume they could.
As a result, the manufacturer with the long haul tried to meet the competitor’s price by putting on the market thinner lumber, thereby equalizing the difference in the freight rates. They still called the product a 2 by 4 even though it was a smaller dimension. The justification was that the original rough lumber before surfacing was a 2 by 4 and therefore the final product could also be called a 2 by 4.
At this point in time, the name 2 by 4 was not reserved for a specific type of board, so there was no legal standard that forced the mills to have a specific dimension for their 2 by 4s. The continuous price wars caused the mills to push the thickness of the 2 by 4 down as much as the market would allow. The name 2 by 4 had a different meaning for every region in the US. The dimensions varied based on the number of sides surfaced, intended use, wood species, location and so on.
Filling up their stockpiles with different versions of 2 by 4s impeded their business so naturally they were the ones that pushed hardest for a nationwide standard. As a consequence, the Department of Agriculture in 1919 set out the Forest Products Laboratory to investigate which dimensions would be most suitable to be adopted as a standard. They investigated 75 mills and gave extended consideration for the most economical thickness of lumber for both manufacturers and customers.
They found out that more than 60% of the producers were surfacing the 2-inch side of their boards down to 1- 5/8, so it was natural to make this dimension a National Standard. Furthermore, they concluded that 1-5/8 is the optimal size for joists and studs and that anything above this dimension would add to the cost but not increase its usefulness.
In 1963, the American Lumber Standards Committee approved the new standard of the 2 by 4 this time being 1-1/2 by 3-5/8 inches. This dimension was later amended once more to the final size used today. Today, a 2 by 4 does start off as a rough cut 2 by 4 but after drying and surfacing the final 1-1/2 by 3-1/2 dimension is achieved which is the one available for purchase in a retail store.
Changes in Production and Shipping
Over a century ago, local manufacturers in the United States produced rough lumber with non-uniform width and non-standard dimensions. Builders would then manually plane the boards on site to fit the project. However, as forests near larger cities were depleted, lumber had to be shipped greater distances, which was extremely expensive at the time. To reduce the weight of the shipment, manufacturers began providing the surfacing at the mill before shipping. This resulted in thinner lumber, which equalized the difference in freight rates. Despite the dimensions varying based on the number of sides surfaced, intended use, wood species, location, and other factors, the product was still called a 2 by 4.
In 1919, the Department of Agriculture set out the Forest Products Laboratory to investigate which dimensions would be most suitable as a standard. They found that over 60% of producers were surfacing the 2-inch side of their boards down to 1-5/8, making this dimension a natural choice for a national standard. They concluded that 1-5/8 is the optimal size for joists and studs and that anything above this dimension would add to the cost but not increase its usefulness.
During World War II, lumber was in short supply, and manufacturers deviated from the standard to produce lumber as cheaply as possible. After the war, the trend of ever-thinner lumber continued, and in 1963, the American Lumber Standards Committee approved a new standard of the 2 by 4, being 1-1/2 by 3-5/8 inches. This dimension was later amended to the final size used today.
Today, a 2 by 4 starts off as a rough cut 2 by 4, but after drying and surfacing, the final 1-1/2 by 3-1/2 dimension is achieved, which is the one available for purchase in retail stores. Despite the reasonable question of why mills don’t start with a slightly larger dimension and surface it down to an exact 2 by 4, the problem was never getting the correct dimension but rather saving on material and shipping costs, which were astronomical back then. The current sizes are well-suited for light-frame construction, roofing joists, and other smaller projects. This history is applicable to all dimensional lumber sizes, with the 2 by 4 being singled out as the most common.
Introduction of the Panama Canal
The Panama Canal is a man-made waterway that connects the Atlantic and Pacific Oceans. It is located in Panama, a country in Central America, and is considered one of the greatest engineering feats of the 20th century. The canal is approximately 50 miles long and consists of three sets of locks that raise and lower ships as they pass through the canal. The construction of the canal began in 1904 and was completed in 1914, after ten years of hard work and the loss of over 22,000 lives due to accidents and disease. The canal has had a significant impact on global trade and has greatly reduced the time and cost of shipping goods between the Atlantic and Pacific Oceans. Today, the Panama Canal remains an important shipping route and a symbol of human ingenuity and perseverance.
Nationwide Standardization
The 2 by 4, the most common piece of wood in the world, is actually not what the name suggests. Its dimensions are 1.5 by 3.5 inches, which may seem misleading to many, especially those outside of North America. However, the reason for this goes back more than a century ago when most dimensional lumber in the United States was produced by local manufacturers and only sold to customers in the vicinity of the mill.
The mills produced rough lumber, which was not uniform in width nor had standard dimensions. Builders were accustomed to manually plane the boards on-site and make them fit the project. By the late 1800s, the forests near the larger cities were depleted, so lumber was not a locally made commodity anymore and had to be shipped greater distances. At this point in time, railroad shipping was still extremely expensive, often double as expensive as the lumber itself, so the manufacturers had to get creative.
They figured out that instead of shipping rough lumber, which is then planed at the construction site, resulting in tons of wasted material, they could instead provide the surfacing at the mill before shipping and, in that way, reduce the weight of the shipment. The opening of the Panama Canal in 1914 further complicated things. This new and considerably shorter shipping route made it possible for mills on the west coast to compete for the east coast markets. Since ocean rates are based on volume, the wood manufacturers had an even greater incentive to start shaving off any volume they could.
As a consequence, the Department of Agriculture in 1919 set out the Forest Products Laboratory to investigate which dimensions would be most suitable to be adopted as a standard. They investigated 75 mills and gave extended consideration for the most economical thickness of lumber for both manufacturers and customers. They found out that more than 60% of the producers were surfacing the 2-inch side of their boards down to 1- 5/8, so it was natural to make this dimension a National Standard. Furthermore, they concluded that 1-5/8 is the optimal size for joists and studs and that anything above this dimension would add to the cost but not increase its usefulness.
In the late 50s and early 60s, a standard was once again open for discussion. Western manufacturers proposed a reduction in the 2-inch side down to 1-1/2 inches while the 4-inch side would remain 3-5/8 as before. Their argument was that the thickness of the board did not affect the bending capacity of the joists much anyway. Whether this was the decisive argument or it was the general will of the industry to go thinner is hard to tell, but in 1963, the American Lumber Standards Committee approved the new standard of the 2 by 4, this time being 1-1/2 by 3-5/8 inches. This dimension was later amended once more to the final size used today.
Overall, the standardization of the 2 by 4 was pushed by retail dealers who were impeded by the various versions of 2 by 4s, which varied based on the number of sides surfaced, intended use, wood species, location, and so on. The Department of Agriculture set out to investigate the most economical thickness of lumber for both manufacturers and customers, which led to the adoption of the 1-5/8 by 3-5/8-inch dimension as a National Standard. The standard underwent several changes over the years, with the current size being 1-1/2 by 3-1/2 inches.
Moisture Content and Dimensional Changes
The moisture content of lumber plays a significant role in its dimensional changes. When lumber is first cut, it contains a high amount of moisture. As the lumber dries, it shrinks in size. This shrinkage can cause issues in construction, especially when the lumber is used for framing.
The standard size for a 2 by 4 is 1-1/2 by 3-1/2 inches. This dimension is achieved after the rough cut lumber is dried and surfaced. However, the moisture content of the lumber can cause the size to change after it has been purchased.
If the lumber is exposed to high levels of moisture, it will absorb the moisture and expand in size. This can cause issues in construction, as the lumber may no longer fit properly. On the other hand, if the lumber is exposed to low levels of moisture, it will dry out and shrink in size. This can also cause issues in construction, as the lumber may no longer provide the necessary support.
To avoid these issues, it is important to properly store and handle lumber. Lumber should be stored in a dry place, away from moisture. It should also be acclimated to the environment in which it will be used before installation. This allows the lumber to adjust to the moisture levels in the environment and minimize dimensional changes.
In summary, the moisture content of lumber can have a significant impact on its dimensional changes. Proper storage and handling of lumber can help minimize these changes and ensure that the lumber provides the necessary support in construction.
Impact of the Great Depression and World War II
During the Great Depression, the demand for lumber significantly decreased, resulting in no major changes or push for a new standard for about a decade. However, during World War II, lumber was in short supply, and manufacturers tried to produce lumber as cheaply as possible, deviating from the standard. There was also a widespread belief that wood had ample reserve strength capacity and that further reducing dimensions would not cause major problems.
After the war, the trend of ever-thinner lumber continued. In the late 1950s and early 1960s, a new standard was proposed by western manufacturers, which reduced the 2-inch side down to 1-1/2 inches, while the 4-inch side remained 3-5/8 inches as before. The American Lumber Standards Committee approved this new standard in 1963, and it was later amended to the final size used today.
Today, a 2 by 4 starts off as a rough cut 2 by 4, but after drying and surfacing, the final 1-1/2 by 3-1/2 dimension is achieved, which is the one available for purchase in a retail store. Despite the continuous price wars that pushed the thickness of the 2 by 4 down as much as the market would allow, the current sizes are well-suited for light-frame construction, roofing joists, and other smaller projects. This history is applicable to all dimensional lumber sizes, but the 2 by 4 was singled out as the most common.
Post-War Dimension Reduction
After World War II, the demand for lumber decreased significantly, causing manufacturers to produce lumber as cheaply as possible. In many cases, they deviated from the standard size of dimensional lumber. There was a widespread belief that wood had ample reserve strength capacity, and reducing the dimensions further would not cause any major problems. As a result, the trend of ever-thinner lumber continued after the war.
In the late 1950s and early 1960s, the standard for the 2 by 4 was once again open for discussion. Western manufacturers proposed reducing the 2-inch side down to 1-1/2 inches while keeping the 4-inch side at 3-5/8 inches. Their argument was that the thickness of the board did not affect the bending capacity of the joists much, and the bending capacity is more influenced by the width. Whether this was the decisive argument or it was the general will of the industry to go thinner is hard to tell, but in 1963, the American Lumber Standards Committee approved the new standard size for the 2 by 4, which was 1-1/2 by 3-5/8 inches.
This dimension was later amended once more to the final size used today. Today, a 2 by 4 starts off as a rough cut 2 by 4, but after drying and surfacing, the final 1-1/2 by 3-1/2 dimension is achieved, which is the one available for purchase in a retail store.
It is reasonable to ask why mills don’t start with a slightly larger dimension and surface it down to an exact 2 by 4. However, the problem was never getting the correct dimension but rather saving on material and mostly on shipping costs, which were astronomical back then. The current sizes are well-suited for light-frame construction, roofing joists, and other smaller projects. This history is applicable to all dimensional lumber sizes, although the 2 by 4 was singled out as the most common.
Final Standardization and Current Size
After decades of inconsistent dimensions and varying sizes across different regions of the United States, a national standard for the 2 by 4 was finally established in 1963. The current size of a 2 by 4 is 1-1/2 by 3-1/2 inches, which is achieved through drying and surfacing the rough cut 2 by 4. This final dimension is the one available for purchase in retail stores.
The decision to standardize the 2 by 4 was based on extensive research conducted by the Forest Products Laboratory of the Department of Agriculture in 1919. They found that more than 60% of producers were surfacing the 2-inch side of their boards down to 1-5/8 inches, which was deemed the optimal size for joists and studs. They concluded that anything above this dimension would add to the cost but not increase its usefulness.
Despite the claim that 1-5/8 by 3-5/8 inches was the optimal size, it is debatable as to whether this is true for all regions and loading conditions across the United States. However, the current size of 1-1/2 by 3-1/2 inches is well-suited for light-frame construction, roofing joists, and other smaller projects.
It is worth noting that the downward pressure on the dimension of the 2 by 4 was largely driven by the need to save on material and shipping costs, rather than achieving an exact 2 by 4 dimension. Nonetheless, the current size has become the industry standard and is widely used in construction projects across North America.
Applicability of Current Sizes
The standard size for a 2 by 4 piece of lumber today is 1-1/2 by 3-1/2 inches, which is achieved after the rough cut has been dried and surfaced. This size is well-suited for light-frame construction, roofing joists, and other smaller projects. However, the history of the 2 by 4 and other dimensional lumber sizes shows that the optimal size for joists and studs is debatable and can vary based on location and loading conditions.
The current size of 1-1/2 by 3-1/2 inches was established in 1963 after a proposal by Western manufacturers to reduce the thickness of the 2-inch side down to 1-1/2 inches. The argument was that the thickness did not significantly affect the bending capacity of the joists, which is more influenced by the width. The American Lumber Standards Committee approved this new standard, which was later amended to the final size used today.
Although the current sizes are suitable for many projects, it is worth noting that the history of dimensional lumber sizes shows that the optimal size can vary based on location and loading conditions. However, the standardization of sizes has made it easier for retail dealers to stock and sell lumber, and the current sizes are widely used in construction projects.
Conclusion
The 2 by 4 is the most common piece of wood used in construction, but its dimensions are not actually 2 inches by 4 inches. The name 2 by 4 comes from a time when lumber was rough-cut and planed on-site to fit the project. However, as lumber had to be shipped greater distances, manufacturers began to surface the wood at the mill before shipping to reduce the weight of the shipment and save on shipping costs. This resulted in thinner lumber being produced and sold as a 2 by 4, even though it was not the standard size.
The Department of Agriculture set out the Forest Products Laboratory in 1919 to investigate which dimensions would be most suitable to be adopted as a standard. They found that more than 60% of producers were surfacing the 2-inch side of their boards down to 1-5/8, so this dimension was made a national standard. The optimal size for joists and studs was found to be 1-5/8 by 3-5/8, and this size was adopted as the standard.
However, the claim that this size was optimal is debatable, and any size can be made optimal by adjusting the spacing of the joists or studs. The moisture content specification was also difficult to enforce, and mills began to surface the lumber green and ship it off as such, resulting in a downward pressure on the dimension of the 2 by 4.
Today, a 2 by 4 starts off as a rough cut 2 by 4, but after drying and surfacing, the final dimension achieved is 1-1/2 by 3-1/2 inches. While some may question why mills don’t start with a slightly larger dimension and surface it down to an exact 2 by 4, the problem was never getting the correct dimension but rather saving on material and shipping costs.
Overall, the history of the 2 by 4 is applicable to all dimensional lumber sizes, and while the current sizes may not be the standard size that the name suggests, they are well-suited for light-frame construction, roofing joists, and other smaller projects.
