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Engineered Floor Joists vs 2×10 Lumber: Compared



V Susan
Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com


Engineered Floor Joists vs. 2x10 Lumber Joists.

Engineered Floor Joists are replacing the traditional 2×10 lumber joists in the USA.

What’s the reason for this preference for Engineered Floor Joists in residential construction?

While both these members serve a similar purpose in house framing, engineered floor joists can span longer than traditional 2×10 joists and have larger holes drilled through them. Additionally, they are lighter and easier to install but are more expensive.

Here’s a quick comparison between engineered and 2×10 lumber joists:

CharacteristicsEngineered Joists2×10 Lumber Joists
StructureMostly in the shape of an I beam. Flanges at the top and bottom, web in the middle. Rectangular-engineered joists are also available.Solid lumber rectangular blocks.
SizeThe 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”
SpansCommonly span 48’, but spans up to 60’ are also available.16’ span is normally available.
InstallationSingle 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.
HolesLarger holes can be drilled Smaller holes have to be made with 2×10 lumber joists.
CostCost more per panel but can reduce the overall cost of a project.Relatively cheaper.
SafetyPotentially hazardous in case of fire.Relatively less hazardous in case of a fire.
SustainabilityLess 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 2×10 Lumber Joists

What are Engineered Floor Joists?

Engineered floor joists are structural load-bearing members used to support floors and roofs in residential construction.

The manufacturing process involves bonding high-grade lumber with adhesives and pressure to enhance the structural integrity of the joists.

The most common type of engineered floor joist is the I-joist.

I-joists are comprised of flanges at the top and bottom which effectively resist bending that may be induced in the structure.

While the web of the I-joist provides resistance against the shearing forces.

However, bear in mind that floor trusses offer more strength than I joists.

Engineered I-joists.
Engineered I-Joists.

What are 2×10 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.

Additionally, 2 x 10 offer great strength at very low costs and are quite durable.

However,2 x 10 can only span up to 16’ as compared to engineered joists which have span lengths of up to 60’.

Traditional 2x10 Lumber Joists.
Traditional 2×10 Lumber Joists.

There are noticeable differences between the two members in terms of uses, installation, costs, and dimensions.

How do Engineered Joists and 2×10 Joists Differ in Terms of Dimensions?

In terms of final dimensions, a standard 2×10 lumber joist does not have an actual proportioning of 2×10.

Rather, after finishing, the final dimensions are 9 ¼” x1 ½”. In terms of length, they only span 16’.

2x10s cannot withstand the self-weight if the span becomes too long.

To increase the span length, you will have to pay much higher than usual.

Traditional Joist Dimensioning.
Traditional Joist Dimensioning

On the other hand, engineered joists are available in lengths up to 48’. 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”.

Engineered Joists Dimensions
Engineered Joists Dimensions

What are the Common Uses of 2x10s and Engineered Joists?

2x10s are commonly used in residential construction to support floors and roofs as they are the most cost-effective option.

However, I-joists are increasingly becoming popular as a replacement for 2 x10s because of their ability to span long distances.

Therefore, they are more suitable for large constructions.

Although the initial cost of I-joists is higher, they may be cheaper in certain cases.

For instance, it is possible to utilize half the number of engineered I-joists compared to 2x10s due to their longer spans, resulting in a reduced overall project cost.

How are Engineered Joists and 2x10s Installed?

Both of these structural members are laid horizontally, with a specific spacing 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 spans 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, engineered joists are relatively easier to install due to their longer spans.

However, engineered joists and 2×10 joists need a rim joist/band joist at the ends for proper load transfer.

Installed Engineered Joists.
Installed Engineered Joists.

Can Holes be Drilled into Engineered Joists and 2×10?

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), you can drill the holes on the web only if they are 1/8” away from the flange.

It is allowable to drill holes with a diameter as large as 1.5 inches, but space them at a distance equal to twice the diameter from the center of the adjacent hole.

Holes in Engineering I joist.
Holes in Engineering I joist.

In contrast,2×10 joists are rather more flexible when it comes to drilling holes.

However, drill the holes 2” away from the ends of the panel and more towards the center.

Also, ensure to drill holes with a diameter that is 1/3 of the depth of the joist.

The diameter of holes allowed to be drilled is about 1/3 of the depth of the joist.

Cost Comparison-Engineered Joists vs 2×10 Lumber

On average, a 2×10 lumber joist costs around $30 for a span of 16’. Engineered joists, on the other hand, cost around $40 for the same length.

Consult your local store for exact pricing.

The cost increases for greater span lengths.

It is also dependent on the availability of the type of joist.

Are Engineered Joists Safer than I-Joists?

Both engineered and 2x10s joists can perform safely if installed properly.

In order to allow load distribution, ensure the joist ends are properly rested on the end walls.

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.

However, over time the joists start to degrade and lose their strength. Thus, it is recommended to have your joists checked and properly maintained after a specific duration.

The panels of joists are not easy to remove and replace, but it is easier to enhance their strengths using certain 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.

Furthermore, engineered joists are not fire-resistant.

They 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 are made from different wood products, while 2x10s are made from a single species of locally grown wood.

Thus more trees are required to be cut down to provide enough material for engineered joists, as compared to 2×10 lumber joists.

These 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.


Engineered joists provide more advantages over 2x10s.

In situations where longer spans, more strength, cost efficiency, and easy installation are required, engineered joists are 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 the project-specific needs and your budget.

Frequently Asked Questions (FAQ)

Do Engineered I-Joists Rot Faster?

When exposed to moisture ,engineered I- joists retain it and do not dry easily.

Therefore,they are more susceptible to rotting than traditional lumber joists.

What is the Lifespan of the Engineered Floor Joists?

The lifespan of engineered floor joists depends on the environmental conditions and maintenance practices.

Generally, engineered floor joists have a lifespan of 60 to 80 years.

How to Determine the Spacing Between Joists?

The spacing of the joists depends on the load requirements and the local building codes.

Closer spacing is necessary for heavier loads.

V Susan
Hi! I'm Susan. I am passionate about woodworking, general DIY and home improvement. If you'd like to connect with me or talk about something you like at mellowpine, drop me a mail at susan@mellowpine.com