How to Replace Subfloor under Load Bearing Wall

To replace subfloor under a load bearing wall, you must first remove enough of the base of the wall to get at the subfloor, cut out and replace the faulty section of subfloor, and then insert a new section of wall to fill the gap. This process may require shimming up the new section to fit tightly with the existing wall.

Replacing subfloor under a load bearing wall can be a challenging task, but it is necessary to maintain the structural integrity of the building. The subfloor is an essential layer that supports the finished floor layer and should not be mistaken for underlayment.

If the subfloor is damaged, it can compromise the safety of the building, and it must be replaced immediately. We will discuss the steps involved in replacing subfloor under a load bearing wall, including removing the wall base, cutting out the faulty section of subfloor, and installing a new section of wall. We will also explore the cost of replacing subfloor and answer some frequently asked questions about subfloor replacement.

Can You Replace a Subfloor Without Removing Walls?

Yes, it is possible to replace a subfloor without removing walls, though it depends on the specific circumstances of the project. Careful planning and professional expertise are essential to ensure the process is completed safely and effectively.

When Is It Feasible?

Partial Damage: If the damage to the subfloor is confined to areas that do not extend beneath load-bearing walls, it is often easier to replace the damaged sections without impacting the walls.
Floating or Non-Load-Bearing Walls: If the walls are not load-bearing, they may be easier to work around, as they don’t rely on the subfloor for structural support. In some cases, the wall baseplates (the part of the wall that sits on the floor) can be temporarily supported to allow access to the subfloor beneath.
Joist Layout and Orientation: The orientation of the floor joists can also affect feasibility. If the joists are laid perpendicular to the wall, it may be easier to remove and replace the subfloor panels without disturbing the walls.

Steps Involved

Assessment of Damage: A thorough inspection is needed to understand the extent of the damage and whether it compromises the wall’s stability.
Cutting Around the Walls: Precision tools like oscillating multi-tools or circular saws can be used to cut along the edges of the walls without damaging them.
Reinforcing Joists: After removing the damaged subfloor, you may need to reinforce the joists or install blocking to provide a sturdy surface for the new subfloor.
Installing New Subfloor Panels: The new subfloor is carefully slid and secured under the existing walls, ensuring it aligns perfectly with the rest of the flooring.

Challenges

Structural Integrity: Ensuring the stability of the walls during and after the process is critical, especially for load-bearing walls.
Accessing Tight Spaces: Cutting and installing subfloor panels under walls can be challenging and may require specialized tools or techniques.
Matching Thickness and Material: The new subfloor must match the existing material and thickness to avoid unevenness, which can impact flooring installation.

If you’re unsure about the process or dealing with extensive damage, consulting a professional contractor is highly recommended.

How Much Does It Cost to Replace a Subfloor?

The cost of replacing a subfloor depends on various factors, including the materials, extent of the damage, and labor rates in your area. Below is a more detailed breakdown:

Factors Affecting Cost

Type of Subfloor Material:
- Plywood: This is one of the most common materials and typically costs between $2 to $5 per square foot.
- OSB (Oriented Strand Board): Slightly cheaper than plywood, with costs ranging from $1 to $3 per square foot.
- Concrete Subfloors: More expensive to repair or replace due to material and labor intensity.
Extent of Damage:
- Localized Repairs: If only a small section is damaged, the costs will be significantly lower than replacing the entire subfloor.
- Widespread Damage: Extensive damage, such as from water leaks, mold, or termite infestations, can drive up the costs due to the need for additional repairs or mold remediation.
Size of the Area:
- A small bathroom or laundry room subfloor might cost between $300 and $800.
- Larger spaces, such as living rooms or kitchens, can range from $1,000 to $3,000 depending on square footage.
Labor Costs:
- Labor costs can vary widely depending on location, but expect to pay between $30 and $75 per hour for a professional contractor.
- Replacing subfloors in tight or complex spaces (e.g., under walls or cabinets) may result in higher labor charges due to the increased difficulty.
Additional Costs:
- Joist Repairs: If floor joists are damaged, repair costs can add $100 to $300 per joist.
- Flooring Removal: If the old flooring needs to be removed, this can add $1 to $3 per square foot to the total cost.
- Disposal Fees: Some contractors charge for hauling away old materials, which can range from $50 to $200 depending on the volume of debris.

Average Costs

On average, a typical subfloor replacement project ranges from $500 to $1,500, but more extensive repairs or larger areas can cost $2,000 to $5,000 or more. For high-end materials or structural issues, the costs can escalate further.

Assessing The Damage

Assessing the damage is the first crucial step in replacing a subfloor under a load-bearing wall. Identifying the problematic areas and determining the extent of damage will guide you in formulating an effective plan for the repair.

Identifying The Problematic Areas

Look for signs of sagging, unevenness, or soft spots in the flooring.
Inspect for water damage, mold, or mildew, as these can indicate underlying issues.
Check for cracks, gaps, or any visible damage in the subfloor around the load-bearing wall.

Determining The Extent Of Damage

Use a level to assess the flatness of the floor and identify any areas that are not level.
Probe the subfloor with a screwdriver to test for rot or softness, especially near the load-bearing wall.
Examine the floor joists and support beams for any signs of damage or deterioration.

Preparing For The Replacement

Replacing the subfloor under a load-bearing wall is a critical task that requires careful planning and preparation to ensure structural integrity and compliance with local building codes. Below, we break down the key steps to prepare for this project:

Obtaining Necessary Permits

Before undertaking any structural work, including replacing the subfloor under a load-bearing wall, it’s essential to check with your local building authority. Most jurisdictions require permits for structural modifications to ensure safety and compliance with building codes.

Why Permits Are Important: These permits not only safeguard you and your property but also provide a paper trail that may be crucial for future home sales or insurance claims. Without proper permits, you risk fines, liability issues, and problems during a property inspection.
What to Expect During the Permit Process: You’ll likely need to submit detailed plans, which may include drawings showing the scope of work, the type of materials to be used, and how you’ll ensure the load-bearing wall remains properly supported during the replacement process. After submitting, you may need to schedule an inspection at certain stages of the project.

Supporting the Load-Bearing Wall

One of the most crucial steps in replacing the subfloor under a load-bearing wall is temporarily supporting the wall to prevent structural issues. The weight of your home, including the roof and floors above, is transferred through these walls to the foundation. Failing to properly brace the wall during the subfloor replacement can lead to sagging, cracking, or even catastrophic failure.

Temporary Support Structures: You’ll need to install a temporary support system, such as adjustable steel columns (jack posts) or a temporary stud wall. This structure should be built parallel to the load-bearing wall and positioned to adequately bear the weight of the structure above.
- Spacing and Placement: Place supports at even intervals to distribute the load evenly. A professional engineer can help determine the precise spacing and size of these supports.
- Tools Needed: Common tools and materials include 4×4 or 2×6 lumber, heavy-duty screws, and a level to ensure proper alignment.
Consulting a Professional: If you’re unsure about how to secure the wall properly, hire a structural engineer or contractor. They can provide guidance or handle the task entirely to avoid potential damage.

Planning the Subfloor Replacement

Once the load-bearing wall is properly supported, you’ll need a clear plan for replacing the subfloor. This preparation involves:

Inspecting the Damage: Before removing the old subfloor, identify the extent of the damage. Water damage, rot, or structural weakening in joists beneath the subfloor should be addressed before proceeding.
Choosing the Right Materials: Select a durable subfloor material, such as plywood or oriented strand board (OSB), that meets building code standards. Consider moisture-resistant materials if the area is prone to dampness, such as near kitchens or bathrooms.
Mapping Out the Process: Create a step-by-step plan for cutting out the damaged subfloor, removing debris, installing the new subfloor, and fastening it securely to the floor joists. Remember to leave a small gap between the subfloor and walls to allow for expansion.

Removing The Damaged Subfloor

When dealing with a damaged subfloor under a load-bearing wall, the process of removal needs to be handled with precision and care to ensure the structural integrity of the building. Here are the steps to follow when removing the damaged subfloor.

Creating Access Points

To begin the process, it’s essential to create access points to reach the damaged subfloor. This may involve removing baseboards, sections of drywall, and any floor covering to expose the subfloor beneath. By creating these access points, you can effectively assess the extent of the damage and plan for the necessary repairs.

Carefully Dismantling The Subfloor

Once the access points are established, the next step is to carefully dismantle the damaged subfloor. This involves removing the sections of the subfloor that have been compromised, which may include cutting out and replacing the faulty subfloor. It’s crucial to work methodically and precisely to avoid causing further damage to the surrounding structure.

Replacing the Subfloor Under a Load-Bearing Wall: Step-by-Step

Replacing a subfloor under a load-bearing wall requires careful planning and execution to maintain structural integrity. Here’s a detailed process to help you tackle this challenging but achievable task:

1. Preparation: Removing Baseboards, Drywall, and Floor Covering

Begin by removing any baseboards and sections of drywall near the load-bearing wall. This provides access to the subfloor and ensures that the structural elements of the wall are not inadvertently compromised during the process. Next, remove the floor covering, such as carpet, laminate, or hardwood, along with any underlayment that might be present. This exposes the damaged subfloor for inspection and replacement.

Pro Tip: Use a utility knife or oscillating multi-tool for precise cutting of drywall, and keep the area clean to avoid debris interfering with your work.

2. Reinforce the Wall Before Subfloor Removal

Before you remove the damaged subfloor, temporarily support the load-bearing wall to maintain the building’s structural integrity. This is often achieved by installing a temporary support wall or a beam with jacks on either side of the load-bearing wall. Ensure the temporary supports are firmly in place before proceeding.

3. Removing the Damaged Subfloor

Cut out the damaged section of the subfloor using a circular saw, making sure to avoid cutting into the underlying floor joists. Pry out the damaged subfloor pieces carefully, and inspect the joists for signs of rot or structural weakening. If joist damage is found, repair or reinforce them before proceeding with the new subfloor installation.

Note: When working around plumbing or electrical lines, proceed cautiously to avoid causing accidental damage.

Choosing the Right Subfloor Material

Selecting the appropriate subfloor material is essential for both durability and functionality. The most common materials for subfloor replacement include:

1. Plywood

Plywood is a durable and widely used subfloor material, offering excellent strength and moisture resistance. Opt for at least 3/4-inch thick plywood rated for subflooring to provide the necessary support under a load-bearing wall.

2. Oriented Strand Board (OSB)

OSB is an economical alternative to plywood and provides similar durability when used as a subfloor. Look for OSB panels that are moisture-resistant and meet structural requirements for your specific application.

3. Specialized Moisture-Resistant Options

For areas prone to dampness, such as basements or bathrooms, consider moisture-resistant plywood or OSB products. These materials can help prevent long-term issues such as warping or mold growth.

Installation and Securing the New Subfloor

Installing the new subfloor correctly is critical to maintaining the structural integrity of your home. Follow these steps for a successful installation:

1. Precise Measurements and Cutting

Carefully measure the space where the new subfloor will be installed, ensuring that it fits snugly against the walls and over the floor joists. Use a circular saw or jigsaw to cut the new subfloor material to the exact dimensions needed.

2. Securing the Subfloor to Joists

Position the new subfloor panels over the joists, ensuring that the edges align with the center of the joists for optimal support. Secure the subfloor using galvanized screws or nails, spaced approximately 6-8 inches apart along the edges and 12 inches apart in the field of the panel.

Pro Tip: Use a construction adhesive along the joists before laying down the subfloor to minimize squeaks and enhance the bond.

3. Shimming for a Secure Fit

If the new subfloor results in uneven surfaces or gaps due to slight variations in the joist height, insert shims as needed to create a level surface. Ensure all shims are securely attached and that the subfloor is flush with surrounding sections.

Final Steps: Finishing the Project

Once the new subfloor is installed and secured, replace the drywall and baseboards you initially removed. Patch and paint the drywall as needed to match the surrounding walls. Finally, reinstall the floor covering or install a new one to complete the project.

Replacing a subfloor under a load-bearing wall is a demanding task, but with proper preparation, quality materials, and attention to detail, you can restore your home’s structural integrity and create a sturdy foundation for years to come.

Reinforcing The Load Bearing Wall

To replace the subfloor under a load-bearing wall, it’s essential to reinforce the wall before removing the existing subfloor. Install temporary support and carefully remove the damaged subfloor. Once the subfloor is replaced, the wall can be repositioned and secured to ensure structural integrity.

Temporary Support Installation

Before replacing the subfloor under a load-bearing wall, it is crucial to reinforce the wall to ensure structural integrity. Temporary support installation is the first step in this process.

Position adjustable steel columns beneath the load-bearing wall.
Use hydraulic jacks to slowly raise the temporary supports to bear the weight of the wall.
Ensure the temporary supports are securely in place before proceeding with subfloor replacement.

Reattaching The Load Bearing Wall

Once the temporary supports are in place, the load-bearing wall can be reattached securely to maintain the structural integrity of the building.

Remove any nails or screws from the existing wall plates.
Reposition the wall plates on the new subfloor section.
Securely fasten the wall plates to the new subfloor using appropriate fasteners.
Remove the temporary supports once the wall is securely reattached.

Inspecting And Testing

Before replacing the subfloor under a load-bearing wall, it’s crucial to thoroughly inspect and test the existing structure to ensure its stability and safety. This step is essential in determining the extent of the damage and the necessary repairs needed to maintain the structural integrity of the building.

Ensuring Structural Integrity

When inspecting the load-bearing wall and subfloor, it’s important to ensure that the structural integrity of the entire system is intact. This includes examining the condition of the wall studs, floor joists, and any support beams. Look for any signs of rot, water damage, or termite infestation that could compromise the strength of the structure.

Checking For Levelness

Another crucial aspect of the inspection is to check for levelness to determine if the load-bearing wall and the subfloor are properly aligned. Using a level, assess the horizontal and vertical alignment of the wall to identify any potential issues that may need to be addressed during the subfloor replacement process.

Final Inspections And Permits

Before completing the replacement of the subfloor under a load bearing wall, it is essential to conduct professional assessments and obtain final approval through inspections and permits. This ensures that the structural integrity and safety of the load bearing wall are maintained.

Professional Assessment

Engage a qualified structural engineer or a licensed contractor to conduct a thorough assessment of the subfloor replacement under the load bearing wall. They will evaluate the structural stability of the wall and provide recommendations for the subfloor replacement process.

Obtaining Final Approval

Upon completing the subfloor replacement, it is crucial to schedule a final inspection by the local building authority. This inspection is to ensure that the work complies with building codes and regulations. Once the replacement meets the necessary standards, the building authority will issue the required permits and approvals.

Conclusion

Replacing the subfloor under a load-bearing wall is a complex but essential task for maintaining the structural integrity of your home. By following the proper steps and seeking professional advice when necessary, you can ensure a successful and safe subfloor replacement project.

Remember to prioritize safety and thorough planning throughout the process to achieve a sturdy and long-lasting result.