What Type of Contractor Can Fix Uneven Joists and Install a New Subfloor?

Paige Bennett
Written by Paige Bennett
Updated July 13, 2022
A woman doing her laundry
Photo: gradyreese / E+ / Getty Images

You should hire a carpenter to fix uneven joists and a flooring contractor to install a subfloor

Get quotes from up to 3 pros!
Enter a zip below and get matched to top-rated pros near you.

If your plan to upgrade to new hardwood flooring hit a snag after discovering unruly and weathered floor joists, you’ll probably need to fork over more cash to reinforce your floor supports before moving forward with any finished flooring upgrade. Sagging floors usually indicate subflooring and floor joist issues. These repairs are significant and require the expertise of a carpenter—not a handyperson. 

Before laying down finished floors, hire a local carpenter specializing in unfinished work to help you with this major home improvement project.

How Do Carpenters Fix Floor Joists? 

Like studs in a wall, floor joists act as the bones of your floor that support your entire flooring system. The subfloor is what gets installed across the joists. So, if your floor joists are uneven, a carpenter will need to level them to prevent further structural issues.

First, the carpenter will inspect the joists and assess the damage. Uneven or sagging floors are often the result of other serious home issues—such as a lack of tie-downs or cross bracing, settlement issues, water infiltration, and poor initial construction.

Depending on your subfloor’s condition, your carpenter will brainstorm a repair plan. Some common subfloor repair options include:

  • Adding plywood or metal to reinforce the frame

  • Sistering the joists by bolting wood or a flitch plate to the joists. 

  • Installing shims—or wedges of wood—to even out the joists. 

However, these are typically temporary fixes, and your carpenter might suggest replacing the joints if sistering or bracing won’t be enough to repair heavily damaged boards. Repairing or replacing joists costs $1,000 to $20,000.

Benefits of Hiring a Carpenter for Floor Joist Repairs

Carpenters specializing in unfinished work should efficiently inspect the structure and find the underlying cause of uneven joists.

If you sister or replace joists without checking for the main issue, you risk leaving the real problem unresolved and paying for a “bandaid” repair. Plus, in certain situations, sistering can damage the added support beams or new joists.

A reputable carpenter will know the right way to safely repair the joists, working around obstacles like plumbing and wiring without causing more costly damage to your home.

Even more, an experienced pro will complete the job quickly, so you can get back to living in your home uninterrupted—and finally choose what type of new flooring you want to lay down.

Can I DIY Joist and Subfloor Repairs?

Subfloor repairs are one of the home projects we definitely recommend leaving to a professional. Attempting DIY joist repairs can be costly and dangerous. You’ll need a hydraulic jack if you plan to sister the joists, and materials alone may cost $300. You’ll also need to work around wiring and plumbing to make the repairs.

If you have a strong carpentry and remodeling background, you can save about $100 to $300 in labor costs per room by installing subfloors yourself. But tread with caution—mistakes may mean spending more money on subfloor materials, and not addressing the real issue could put you back at square one with uneven or sagging floors. Plus, this project can take several days for the average person.

If you’ve got your heart set on a DIY, opt to lay down your own flooring after a pro deems your subfloor and joists safe, which you can do for about $3 to $7 per square foot.

Can I Hire a Flooring Specialist for Subfloors?

Given the complexity of subfloor repairs, you should really stick with a carpenter for this project. But if you want to install a new subfloor or underlayment over sound floor joists, hire a local flooring contractor for this step. Replacing subfloors costs $3 to $10 per square foot. This project is essential to ensuring your floors are level and structurally sound.

Need professional help with your project?
Get quotes from top-rated pros.