How Much Does It Cost to Replace a Rotted Support Beam?

Ginny Bartolone
Written by Ginny Bartolone
Updated January 11, 2022
Exposed ceiling support beams in home
Photo: Iriana Shiyan / Adobe Stock

Replacing a rotted support beam will cost an average of $3,250 depending on the material, cause of the damage, and structure of your home

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The framework of your home is just as crucial to its stability and longevity as your foundation. When dry rot, water damage, a shifting house, or even pests cause a wooden support beam to weaken, it's time to call in a structural engineer. The cost to replace a support beam can run between $1,500 and $5,000 on average but may run much higher for complex replacements.

How Much Does It Cost to Replace a Rotted Support Beam by Square Foot?

Support beams are the horizontal rafters that connect to vertical joists and columns. They are found in your home’s roof, ceiling, walls, floor, and garage. There are many factors that contribute to the cost of identifying, removing, and replacing a rotted beam. On the most basic level, start by considering the cost of materials for the beam itself. 

Depending on your home’s structure, age, and unique needs, your contractor may recommend natural wood, manufactured wood, or even steel beams to replace the rotted culprit.

The ranges below take the width and variety of the material into account:

MaterialCost per Square Foot
Laminated veneer lumber (LVL)$3 – $12
Glulam$6 – $40
Natural wood$5 – $90
Steel I or H beam$6 – $80

In addition to the cost of the beams, remember to add an average of $1,000 to $5,000 for labor.

How Much Does It Cost to Replace a Rotted Support Beam Yourself?

Replacing a structural element of your home is not advisable, especially for load-bearing support beams. In most areas, and especially in condos or housing developments, you'll likely need to call a licensed and certified contractor to obtain a permit for the work and handle the project.

You can address issues that may impact the structural integrity of your home or escalate project costs by watching for signs of termites, dry rot, or the need for foundation repair—call in a pro to help get these resolved as early on as possible.

Support Beam Replacement Cost Breakdown

The process of replacing a support beam always begins with diagnosing the extent of the problem. Start by calling your local foundation repair experts the moment you detect sagging floors, large cracks in your walls or ceiling, or can spot the rot on an exposed beam.

From the first visit to the final touches, expect the following line items:

  • Permits and inspections

  • Structural engineer report

  • Temporary support beams

  • Drywall removal to access beam

  • Replacement beam materials

  • Replacement beam labor

  • Replacing drywall, paint, or surrounding decor

If the rot in your beam stemmed from a larger issue—like termites, dry rot from fungus, or the dreaded water damage—add the cost of these repairs to the replacement. We'll cover this more below.

How Much Does It Cost to Replace a Beam by Type of Damage?

In the best-case scenario, the rot does not extend beyond a single beam. A trained structural engineer will be able to identify what led to the rot and how much additional work you should expect.

Dry Rot

Despite its name, dry rot is a form of fungi that flourishes in moist and humid areas. The outside of the wood may look dry, hence the name, but contains fungus that breaks down the cellulose of the wood. 

In addition to the $1,500 to $5,000 to replace the damaged beam, expect to pay between $1,000 and $3,500 for extensive fungi removal for the surrounding area.

Termites

The threat of termites can really keep a homeowner up at night. These wood-consuming insects can quickly multiply and threaten the structure of your home in both support beams and the surrounding planks, columns, or floor joists. Termite control typically costs between $1,300 and $1,780.

Water Damage

From flooding and storms to a burst water main line, water damage can do a number on natural wood, especially for load-bearing beams. Water damage can cost between $1,200 and $4,600 depending on the extent of the issue.

Sinking, shifting, and cracked foundations can also lead to problems with structural beams, especially those already experiencing rot. 

If you experience extreme changes in your foundation—or if the beams were incorrectly installed in the first place—this could lead to overloading the beam itself. An excessive amount of weight on all or one part of the beam may threaten its integrity.

Depending on the extent of the issue, add an average of $4,530 to the cost of replacing the foundation beam itself.

What Factors Influence the Cost to Replace a Rotted Support Beam?

Person fixing steel support beam
Photo: Daisy Daisy / Adobe Stock

These unique contributing factors have the most say in the cost to replace a support beam. When you meet with your local carpenter or structural engineers, they'll be looking at the following factors to determine your estimate.

Access to the Beam

An exposed beam in the center of your living room is much easier to replace than one in a crawl space. In this case, the contractor will simply add temporary support posts and remove the old beam. Beams inside walls or under flooring and subflooring require more labor, while crawl space and basement supports are the trickiest to access, adding to the time required for the repair.

Additionally, if your contractor needs to work around things like electrical wiring and plumbing, they might call in an electrician or plumber to ensure everything is in working order before closing up the space.

Weight-Bearing Load

Load-bearing walls will likely cost more to repair than non-load-bearing beams that separate two rooms. Contractors may be required to spend more time stabilizing the structure before completing the work—increasing the price for both labor and materials.

Material and Size of the Beam

Your engineer may recommend a specific material and thickness for your new beam. For example, beams bearing a great deal of weight or those susceptible to termites might be best replaced by a manufactured wood or steel beam.

Regional Factors

Lastly, where you live can play a role in the price to replace a rotted support beam. 

In addition to basic differences in the cost of living around your area, expect varying prices based on:

  • Whether you live in an older home

  • Local permits costs

  • Access to materials

  • Regional weather

FAQs About the Support Beam Costs

How do I replace a rotted support beam?

Load-bearing elements of your home, such as the horizontal beams that run along your floors, walls, roof, and ceilings, should be inspected by a trained structural engineer. 

Call on these experts the moment you detect rot, water damage, or foundation issues in your home. If the beam does need to be replaced, your contractor will likely install temporary support to the area while replacing the beam with new wood or steel.

Why should I pick steel for my new support beam?

Contractors may recommend upgrading your old rotted wood beam with steel for a few reasons. While steel is more expensive than other materials, it offers the following benefits:

  • Fire-resistant

  • Unaffected by pests

  • Longer-lasting

  • Stronger against water damage (when galvanized against rust)

What other projects should I do at the same time?

Detecting a weak or rotted beam is a great time to look into the underlying cause. Bring in experts to double-check for high moisture levels that lead to dry rot, encapsulate your crawl space or basement, or inspect your property for wood-damaging pests.

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