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Steel Floor Joists Guide: Suitable for Homes?



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


Steel Floor Joists.

Steel floor joists are horizontal load-bearing structures that transfer loads from floors above them to beams. Their high strength-to-weight ratios ensure a stable structure. Moreover, they are durable and resistant to moisture, mold, and pests. However, they are not common in residential buildings due to cost considerations.

Steel Floor Joists.
Steel Floor Joists

Advantages and Disadvantages of Steel Floor Joists

Advantages of Steel Floor JoistsDisadvantages of Steel Floor Joists
High-Strength-to-Weight RatioCorrodes easily
Resistant to moisture, mold, and pestsLimited availability
Reduced noise and structural stabilityExpensive
Low maintenance Higher heating and cooling costs
Fire-resistantSusceptible to lateral torsional buckling
Remain stable during earthquakes and hurricanesNot Flexible
Easily recyclable Difficult to transport
Advantages and Disadvantages of Steel Floor Joists

Advantages of Using Steel Floor Joists

High Strength-to-Weight Ratio

Steel has the highest strength-to-weight ratio among all the materials used in construction.

This means that lesser amounts of steel can bear more loads compared to other materials, thus needing fewer supporting members.

This, in turn, reduces construction time, labor costs, and the volume of required material.

Steel having large load-bearing capacities can be used in cases where wood is not sufficient to resist heavy loads.

Moreover, a traditional lumber joist’s maximum span is much lower than a steel joist’s.

Resistance to Moisture, Mold, and Pests

Locations such as basements, roofs, and attics are all particularly prone to degradation. This leads to the rotting and wearing of wooden joist members.

To prevent damage, you can dry the joists.

It is best to use low-pressure fans in conjunction with dehumidifiers to maintain a dry environment.

In comparison, steel floor joists are more resistant to moisture effects and do not grow mold under them.

Steel floor joists are also resistant to rodents, termites, and other pests.

This makes steel a great material choice for basement beams in residential construction.

Reduced Noise and Structural Stability

Incorporating steel floor joists in flooring systems makes them quieter.

The squeaking noise that is observed while walking on traditional floors is due to the wear, warping, splitting, and cracking of the floor joists, which loosens the nails and bolts.

Steel joists can maintain their straight shapes and remain structurally sound for long periods.

Additionally, the bolts and nuts applied to steel floor joists are fewer and tighter than the ones used in wooden joists.

They are also less susceptible to sagging than wooden floor joists.

Low Maintenance

Once installed, steel floor joists maintain their strength for an extended period, reducing the need for frequent replacement.

Additionally, their use under floors demands minimal maintenance.

Fire Resistance

Steel floor joists are more resistant to fire as compared to wooden joists, as steel is a non-combustible material.

A good way to better protect steel joists is to coat them with fire-resistant chemicals, which allow them to be heat resistant even at very high temperatures.

High-density Spray-Applied Fire Resistant Material (SFRM) is a common chemical protection compound used to protect steel joists in the USA.

Fireproofing of Steel Joists
Fireproofing of Steel Joists

Location Specific Advantages

In areas prone to hurricanes and earthquakes, steel joists are a viable option.

They help to maintain the stability of structures during these conditions.


Steel can be recycled easily.

Moreover, they allow for energy-efficient construction with minimal impact on the environment.

Disadvantages of Using Steel Floor Joists

Corrosion of Steel

Steel is a highly corrosive substance. When exposed to moisture for long periods, it starts to rust.

To prevent corrosion, steel floor joists have to be painted periodically.

If not coated properly, steel joists lose their thickness at a rate of approximately 0.04 inches/year to 0.06 inches/year, ultimately leading to the collapse of the floor.

Corrosion of Steel Member.
Corrosion of Steel Member

Availability and Initial Costs

In certain areas, there will be limited availability of steel.

Moreover, they also have higher investment costs than other alternatives like wood.

Thermal Conductivity

Steel has high thermal conductivity, resulting in higher heating and cooling costs.

Additional insulation is necessary to maintain the comfort of your home.

Buckling of Steel Joists

Buckling is a failure mechanism characterized by the bending of a structural member due to a compressive load surpassing the critical limit.

While steel is good both in tension and compression, it is susceptible to lateral torsional buckling due to applied loads.

This is because the average steel floor joist member is more slender as compared to its counterpart.

Limited Design Flexibility

Generally, steel joists are available in standard sizes and shapes in accordance with different codes.

Therefore, the customization of these joists is quite challenging.

Difficult to Transport

Since steel joists are heavier, they are difficult to transport to the construction site.

Additional labor and equipments are also necessary during the installation process.

Are Steel Floor Joists Better than Traditional Wood Joists?

Steel joists offer a variety of advantages over traditional wood joists.

PropertySteel Floor JoistsWooden Floor Joist
Moisture ResistanceHighLow
Mold DevelopmentNoneYes

Steel vs Wooden Floor Joists

Cost of Steel Floor Joists

Steel floor joists come at a cost of $100 to $400 per foot for residential construction.

As the floor span increases, steel floor joists become more expensive.

The cost also depends on the type of steel used.

Hot-rolled steel joists are thinner and less expensive, whereas cold-formed steel joists are thicker and have more strength but are also more costly.

The total cost of installing steel floor joists, including material, transportation, labor, and installation costs around $10,000 to $20,000.

Types of Steel Floor Joists

Open web steel joists are the most common type of steel floor joists.

These joists generally have a depth between 8” to 30” and span up to 60’.

Open Web Steel Joist.
Open Web Steel Joist

Different types of open web steel joists are:

  • K-Series
  • KCS-Series
  • LH-Series
  • DLH-Series
  • CJ-Series

While the K-series is common for residential applications, the KCS-series is a subset of the K-series.

It is common in situations with shorter-span requirements, where there is a need to adhere to shear and bending moment requirements.

Long-span-steel joists, or LH series, and Deep-long-span joists, or DLH series, are lightweight alternatives that longer span.

Among LH and DLH series, DLH series have longer spans covering over 100 feet.

In CJ series joists, steel and concrete are used to create a strong flooring system.

Frequently Asked Questions (FAQ)

Can I Replace the Floor Joists Without Removing the Floor?

It is possible to replace floor joists without removing the floor.

However, it is crucial to adequately support the floor using various techniques like sistering to prevent the collapse of your floor.

Are Engineered Floor Joists Better than Steel Joists?

Engineered floor joists are a more cost-effective and lightweight option than steel joists.

However, they are more expensive than wooden joists and are not as durable as steel joists.

Can I Use LVL for Floor Joists?

Laminated Veneer Lumber, or LVL, is a common choice for floor joists that reduces the risk of warping and shrinking than traditional joists.

They are created by bonding multiple layers of wood veneers under heat and pressure.

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