Basement Beams Guide: How to Replace Them

Basement Beams Guide: How to Replace Them

Basement Beams Guide: How to Replace Them

Basement beams are the main load-bearing beams found in the basement of a house. They carry all the loads from above them and transfer them to the foundation. With time, basement beams tend to degrade and have to either be replaced or reinforced.

If basement beams undergo significant degradation, it becomes quite inconvenient and can also be dangerous.

This article is aimed at guiding homeowners to figure out the state of their basement beams and help with their replacement and reinforcement.

What are Basement Beams?

Basement beams carry the load from joists above them. This load is quite heavy and thus removing a basement beam can cause the floor above it to collapse.

Hence, it is not easy to replace basements beams. They are instead reinforced with metal plates.

All load-bearing wooden members including basement beams and posts tend to develop cracks over time.

In homes that are older than a hundred years, it is a common sight to see large cracks in the beams and posts.

Some cracks are large enough for a whole thumb to fit right through them.

In such a situation, homeowners need to know when and how to replace or reinforce the beams in their basements.

Basement Beam and Column Post.
Basement Beam and Column Post.

How to Replace Basement Beams?

Basement beams are an integral part of a house, carrying the floor loads above them.

Cracks tend to develop over time in basement beams and columns and they start to lose their strength.

Moisture and water leakage tend to worsen the structural integrity of basement beams.

Especially in basements where there's a likelihood of flooding such as walkout basements.

This loss of strength causes the floor to sag.

In such instances, it becomes necessary to replace them.

The following steps can be followed to replace a basement beam without causing any damage to the entire frame of the basement.

Step1: Set up Temporary Support

The first step is to identify the beams in your basement.

Most basements are semi-finished or unfinished, which means beams are likely to be exposed and visible.

Otherwise, you'll need to remove any kind of ceiling that's covering the beam.

Basement beams are load-bearing and removing them without setting up any temporary support can cause the floor above them to collapse.

The first step in replacing a basement beam is to set up a temporary support wall.

Usually, a timber wall is set up on both sides of the basement beam to act as a substitute load-bearing member.

Vertical lumber panels are nailed into the horizontal beams on the top and bottom of the wall.

Temporary Wall Support.
Temporary Wall Support

Step 2: Relocating the Jack Post

The jack posts supporting a basement beam are to be removed while replacing the beam.

When this happens, the same location of the jack posts cannot be used again because it would have lost its bearing strength.

Select new locations for the jack posts, under the beam.

Dig out the material from the marked location and pour concrete into it to solidify it.

Step 3: Cut a New Beam for Replacement

Measure the dimensions of the old beam that needs replacement.

Order a new beam and cut it into the required size.

In most cases, basement beams are made from lumber.

It is possible that the size of the old beam may not have been enough to carry the floor load and has thus cracked.

If such a possibility exists, then it is recommended to replace it with a steel I-beam instead of a wooden beam.

Step 4: Remove the Old Beam

Remove the jack posts supporting the existing cracked beam and start removing the beam itself by cutting it into small pieces.

Cutting this way ensures that the temporary support wall is sufficient to hold the weight above.

Cutting of Old Basement Beam.
Cutting of Old Basement Beam.

Step 5: Place in the New Beam and Posts

Place the jack posts into the new location and drill them in. Bring in the new beam and place it above the posts.

Fasten the beam accordingly to the edges of the support and tighten the top plates of the posts against the bottom of the new beam.

Pour concrete into the hollow posts if you require more strength. Drill the posts into the new beam and start removing the temporary support walls.

Steel I-beam Installed in Basement.
Steel I-beam Installed in Basement.

How to Reinforce Basement Beams?

Generally, it's more economical to reinforce a basement beam than to replace it entirely.

Here's how to reinforce basement beams.

Step1: Installing New Jack Posts

When a basement beam is reinforced with steel plates, it makes it much heavier.

For this reason, the existing jack posts in the basement may be insufficient.

Therefore, as the first step install more jack posts and place them at equal intervals to distribute the load equally.

Check the alignment of the posts with a leveling instrument.

Make a tight connection between the top plate of the posts and the bottom of the beam by tightening the bolts.

Step 2: Reinforcing with Metallic Plates

Reinforce the weakened sections of a basement beam by installing metallic plates on both sides of it.

These sections include ones that are damaged or have to bear heavy loads.

A full-length steel plate can also be installed to strengthen the basement beam if required.

Holes are to be drilled every 8” distance along the length of the plate.

Connect the plate to the sides of the beam by using bolts.

Reinforcing Beam with Steel Plates.
Reinforcing Beam with Steel Plates.

Step 3: Repairing Weakened Sections

The weakened sections of basement beams can be repaired by using parts of new lumber to replace them.

This can be done by placing temporary jack posts to hold the beam and then cutting the damaged sections of the beam to remove them.

Cut the rotted area at 1” intervals using a circular saw and then remove it.

Then cut a replacement piece out of new wood and place it into the cut area of the basement beam.

The surface of the new piece is covered with an epoxy wood adhesive and is then placed into the cut area and nailed into the old beam with 4” long nails.

Keep the size of the new wood section bigger than the cut area to have it put tightly in place.

Let the adhesive dry for a day and then remove the temporary jack posts.

Overall, strengthening a basement beam is much more difficult compared to strengthening floor joists.

When Should you Replace the Basement Beams?

Basement beams and posts should be replaced when they develop substantial cracks and start settling. A basement beam or post is declared as a “failed” one if it has a crack with a length greater than its width.

For example, if an 8” beam has a 10” crack, then according to building codes it has failed.

It's common for basement beams in older houses to fail this standard. But it's not necessary to entirely replace these beams, rather they can be reinforced and protected.

On the other hand, replacement is called for when there are obvious signs of settling and sagging in the beam, in addition to large cracks.

Cracks in Basement Beams
Cracks in Basement Beams

The settlement of basement beams causes sloping in the floors above them known as “deflection”.

Deflection makes the floors above uneven.

This deflection is the key reason for replacing basement beams in most homes.

Another situation when a replacement becomes necessary is when there's leakage into the basement.

If the basement beams are made of wood and have been exposed to too much moisture, they will start to rot and lose their bearing capacity.

A great way to prevent moisture from leaking into your basement is to construct a basement knee wall.

Even steel beams can rust quite badly if not maintained well.

Replacement for basement beams is also done when homeowners decide to make renovations to the design of the basement.

To get a larger, obstruction-free basement, existing posts in the basement will sometimes need to be removed.

Replacing the basement beam is often necessary if posts are to be removed.

The replacement is then done with a larger and stronger beam, either a wood beam or a more compact steel beam that reduces the number of support posts required.

How Much Does it Cost to Replace Basement Beams?

A simple basement beam replacement project is likely to cost around $7000 to $8000.

But if there is a need to set up temporary walls, the overall cost can reach up to $25000.

The cost of replacing basement beams varies with the complexity of the situation.

Replacing a wooden beam with a newer wooden one is simple and will not cost a lot.

But, if you want to replace a wooden basement beam with a more compact but stronger steel beam to create more space, then the cost increases.

Replacing a basement beam is generally categorized as a special structural foundation repair process, requiring structural engineers for inspection.

This means the cost of the project will also depend on the recommendations of the engineer.

The engineer will make considerations including the required size of the new beam, the number of posts, the placement of posts, etc.

The need to set up temporary wall supports while replacing the basement beam is a major contributor to the cost of the project.

Add to that, the cost of relocation of HVAC ducts and electrical wiring.

All these considerations factor into the total cost of replacing a basement beam, and the final cost of such a project may rise up to $20,000-$25,000.

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Do You Need a Permit to Replace Basement Beams?

Yes, you require a permit to make any structural changes to the basement of your house.

There are a number of reasons in addition to legal issues, that make it necessary for you to get a permit before having your basement beams replaced.

First of all, the replacement work permitted by the city is safe and reliable.

It is done by engineers who are equipped with the right technical knowledge and skills.

You can hire a contractor to get a general idea about the repairs and changes that your beam requires but do not start the work on his recommendations.

If a contractor advises you that your repair work is small and does not require a permit, then it should be a clear red flag.

Secondly, it is to be noted that only permitted repair works increase the value of houses.

As part of a sale, there are repair disclosures that must be legally revealed to potential buyers.

Foundation is the first thing that comes up during inspection.

Thus, having made unpermitted repairs to basement beams may cause them to not go for the sale.

So, if you are trying to sell your house, then only documented repairs will add to its value.

Any unpermitted repairs and work can lead to a decreased value of your house and become more expensive for you as a seller as you try to gain the buyer’s approval.


Basement beams are an integral part of a house. They are the main load carriers for floors above them.

Due to degradation, basement beams may need to either be reinforced with metal steel plates or replaced entirely.

The beams can undergo degradation due to leakage or simply due to being old.

The replacement can be done by using stronger wooden beams or steel I-beams.

The steps required for replacing and reinforcing basement beams have already been explained above.

Generally, it is encouraged to reinforce basement beams using steel plates, because the replacement process can become complex and expensive.

The Replacement process is only initiated when there are clear signs of sagging in the floors, or when the homeowners need to make renovations and design changes.

The cost of replacing basement beams depends on the complexity of the process.

It is important that the replacement process is carried out with a permit to ensure the safety of the house and to maintain or increase its price.

Frequently Asked Questions (FAQ)

What Kind of Steel Plates Should be Used to Reinforce Basement Beams?

Angle steel plates are the most preferred type of plates that are used to strengthen basement beams.

They are “L” shaped plates that can easily be attached to beams by drilling holes and using bolts.

Can You Use I-Beams in a Basement?

I-beams can be used effectively as basement beams.

The flanges of the I-beam are good for resisting bending moments, while the web resists shear forces.

Steel I-beams offer great strength and thus are sufficient to resist basement floor loads.

How Long Do Wooden Beams Last?

Wooden beams can last anywhere between 50 to several hundred years depending on the care that is provided to them.

The duration of wooden beams depends on the type of wood used, the quality of the construction, the repairs provided to it, and the local climate.

About 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

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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

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