While a 2x10 has been traditionally the most popular lumber size for joists in the USA, they are increasingly being replaced by Engineered Floor Joists.
What's the reason for this preference for Engineered Floor Joists in residential construction?
Engineered floor joists can span longer than traditional 2x10 joists and can have larger holes drilled through them. Engineered joists are lighter and easier to install although they are more expensive. Both these members serve a similar purpose in house framing.
Engineered joists commonly come in the shape of I-beams.
These I-shaped joists are engineered with lengths of 60 feet or more and can be cut into any required siz.
Due to such long lengths, a single batch of engineered I-joists is enough to meet framing requirements for a house.
Here's a quick comparison between Engineered Floor Joists and 2x10 Lumber Joists:
|Property||Engineered Joists||2x10 Lumber Joists|
|Structure||Mostly in the shape of an I beam. Flanges at top and bottom, web in the middle. Rectangular engineered joists are also available.||Solid lumber rectangular blocks.|
|Size||The depth of an engineered I-joist range between 9 ½” to 16”, whereas the width ranges from 2 ½” to 3 ½”.||The final dimensions for traditional joists are 9 ¼” x1 ½”.|
|Spans||Engineered joists commonly span 48’, but spans up to 60’ are also available.||16’ span is normally available.|
|Installation||Single long spans are enough to meet the framing requirements of a house, making it easier to install engineered Joists.||Installation is relatively harder as two sets of 2x10s are to be installed to meet the total house span.|
|Holes||Larger holes can be drilled in engineered joists.||Relatively smaller holes have to be made with 2x10 lumber joists.|
|Cost||Engineered joists cost more per panel but can reduce the overall cost of a project.||2x10 are relatively cheaper.|
|Safety||Potentially hazardous in case of fire.||Relatively less hazardous in case of a fire.|
|Sustainability||Less environment friendly, as more trees need to be cut down to generate enough material for engineered joists.||More eco-friendly, as a single large tree can be used to make traditional joists|
Differences Between Engineered Joists and 2x10 Lumber Joists
What are Engineered Floor Joists?
Engineered floor joists are structural load-bearing members used to support floors and roofs in residential construction.
They are synthesized from engineered wood together with standard lumber to form a lighter yet stronger joist panel.
The most common shape given to engineered floor joists is that of an I-beam. I-joists meet the demanding standards and perform well as load-bearing members.
I-joists are comprised of flanges at the top and bottom which effectively resist any sort of bending that may be induced in the structure.
While the web of the I-joist provides resistance against the shearing forces.
But bear in mind that floor trusses offer more strength than I joists.
What are 2x10 Lumber Joists?
2x10s are the standard members that have been used in residential construction for a very long time.
They are made from different local woods such as spruce, fir, and pine among others.
Although 2x10s have a nominal size of 2"x10", the actual size is usually 1-½"x 9-¼".
These have been the standard for a very long time. They offer great strength at very low costs and are quite durable.
They only span up to 16’ as compared to engineered joists which have span lengths of up to 60’.
It's much cheaper to use 2x10 joists compared to engineered joists.
How do Engineered Joists and 2x10 joists differ in terms of dimensions?
In terms of final dimensions, a standard 2x10 lumber joist does not have an actual proportioning of 2x10.
Rather, after finishing the final dimensions are 9 ¼” x1 ½”. In terms of length, they only span 16’.
To increase the span length, you will have to pay much higher than usual.
Engineered I Joists are available in lengths up to 48’ commonly. However, 60’ lengths are also possible with these joists.
The depths of I-joists range between 9 ½” to 16”, whereas the widths range from 2 ½” to 3 ½”.
The depths of I-Joists copy the standard depth of 9 ½” as for 2x10 joists but can be readily increased up to 16”. The webs can also be made thicker.
As discussed before, due to the durability of engineered wood, they offer longer spans to be cut.
On the hand, 2x10s cannot withstand the self-weight if the span becomes too long.
As such, normally 2x10s are found in spans of 16” whereas the I-joists come in spans of up to 48’.
What are 2x10s and Engineered Joists commonly used for?
2x10s are commonly used in residential construction to support floors and roofs.
They are still being applied abundantly due to the fact that they remain the cheapest option available.
I-joists on the other hand, are increasingly becoming popular as a replacement for 2x10s.
I-joists offer greater span lengths but are more expensive. In some cases, however, they may prove to be cheaper than 2x10s.
For instance, it is possible to utilize half the number of engineered I-joists as compared to 2x10s, as they span longer. This reduces the overall cost of the project.
How are engineered joists and 2x10s installed?
For the most part, both of these structural members are laid horizontally and specific spacing is provided between them.
However, there are some differences relating to an engineered I-joist's unique profile.
When installing I-joists, they are most likely to be rested on the block wall for the main support.
If they rest on the framing, then their flanges are required to be nailed into the wood.
To strengthen the I-joists, some contractors may choose to sister the joists or use blocks to fill the gaps between the joists.
2x10s are installed in a similar fashion, with the exception that they run from the support wall to the central beam support.
Then another set of 2x10s span from the central support to the other end wall. 2x10s overlap at the center.
2x10s are nailed into the main beam and sill plate. Blocking and sistering can be introduced if desired. The spacing of joists is kept at 16” to 24”.
Overall, it can be claimed that the engineered joists are relatively easier to install due to their longer spans.
Can Holes be Drilled into Engineered joists and 2x10?
I-joists become quite restricted when it comes to drilling holes in them. The flanges of an I-joist are off-limits when it comes to notching.
The web on the other hand, allows for holes to be drilled but under certain standards.
According to the International Residential Code (IRC), The holes can be drilled on the web only if they are 1/8” away from the flange.
Holes of diameter as big as 1.5” can be drilled but they must be spaced at a distance equal to twice the diameter from the center of the adjacent hole.
2x10s joists are rather more flexible when comes to drilling holes.
But the holes must be ensured to be drilled 2” away from the ends of the panel and more towards the center.
The diameter of holes allowed to be drilled is about 1/3 of the depth of the joist.
Since engineered joists offer more strength, larger holes can be drilled into them. Even rectangular holes can be withstood by I-joists.
Engineered joists clearly offer an advantage over the 2x10s when it comes to drilling holes, as larger and differently shaped holes can be drilled into them.
Cost Comparison-Engineered Joists vs 2x10 Lumber
On average, a 2x10 lumber joist costs around $30 for a span of 16’. Engineered joists on the hand cost around $40 for the same length.
Note that lumber prices vary all the time and you need to consult your local store for exact pricing.
The cost increases for greater span lengths.
Cost is also dependent on the availability of the type of joist as well.
A 2x3 flange I-joist is more common and readily available, whereas a 2x4 flange I-joist is rare and thus would cost a lot more.
In cases where heavy loads are to be supported, common 2x3 flanged I-joists might not be enough.
Both engineered joists and 2x10 joists need a rim joist/band joist at the ends for proper load transfer.
Are Engineered Joists Safer than I-Joists?
Both engineered and 2x10s joists can perform safely if installed properly.
As long as the codes are followed, the joists will behave predictably.
The joist ends must also be rested well on the end walls to allow load distribution.
According to the IRC, if the joists are resting on a bearing area of under 3", they will act with a reduced capacity. In contrast, if they rest on 3” they will transfer loads efficiently.
Since joists are an integral part of residential construction, it is always preferable to provide a few extra panels.
Over time the joists start to degrade and may lose their strength. Thus, It is strongly advised to have your joists checked and properly maintained after a specific duration.
The panels of joists are not easy to remove and replace, but their strengths can be increased readily via some techniques.
A few common ways to do so include blocking, sistering, plywood application, metal wrapping, steel reinforcement, and mid-span beam support.
Joists can be made significantly stronger with these strength enhancement techniques, and their wobbling effects can be reduced considerably.
When you want exceptional strength, open web floor trusses are a good choice compared to traditional joists.
Finally, when it comes to fire hazard safety, engineered I-joists are at a disadvantage.
Engineered I-Joists have webs made of Oriented Strand Board (OSB), which is likely to burn more in case of a fire.
Are Engineered Joists More Sustainable than 2x10s?
Overall, 2x10s are more sustainable, but due to profitability, companies tend to mass-produce engineered wood products.
Engineered joists can be drafted using a mix of woods while 2x10s are made from a single specie of locally grown wood.
Thus more trees are required to be cut down to provide enough material for engineered joists, as compared to 2x10 lumber joists.
The trees used in making joists can be regrown easily.
An even more sustainable option would be steel joists, however, they're uncommon in residential construction.
After drawing a comparison between engineered joists and traditional 2x10s, it is clear that engineered joists provide more advantages over 2x10s.
In situations where longer spans, more strength, cost efficiency, and easy installation are required, engineered joists are clearly the better choice.
But there are cases where 2x10s become preferable due to their cheaper cost and some specific advantages.
The right choice depends on your situation and the amount you are ready to spend on your floor support system.
Frequently Asked Questions (FAQ)
Do Engineered I-joists rot faster?
Engineered wood joists cannot absorb small leaks. Thus, when it becomes wet inside a wall cavity, it is likely to stay wet which prompts faster rotting as compared to traditional lumber joists.
How long can you span using engineered joists?
Spans of up to 60’ are possible with engineered wood joists.
Why are engineered joists given the shape of an I-beam?
The I-beam shape splits the engineered joists into two sections. The two flanges resist bending or flexural stresses, and the web resists shear forces effectively.
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