How Much Does a Floor Joist Repair Cost?

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Inside most homes, floor joists, which are the shafts that support the floors you walk on, often rot, sag, become bouncy or could be ruined by pests.  If this were the case, then you will more than likely need a contractor to come in and fix the situation.

Floor Joists by Sery Content Development, on Flickr
Floor Joists” (CC BY 2.0) by  Sery Content Development

How much does floor joist repair cost?

The costs of repairing the floor joists will depend on the number of joists that need to be replaced, the situation, the contractor performing the job and where you live.  If you only needed to repair a few rotted joints, a contractor will often use a process that’s known as “sistering,” a process which cleans away the rot and the affected timber is treated to prevent rot in the future.  A new joist will then be attached to the rotted one and will be fastened to it.  Depending on the damage and access to the joints, the sistering method can cost about $150 to $325 per joist.  For the average room, if every joist needed to be sistered, you could be looking at a $1,250 to $3,500 bill.

If the joists have been heavily damaged, then a house may need to be jacked up in order to remove and replace all of the affected joists.  If this were the case, the costs could easily be in the $15,000 to $35,000 range, again, depending on so many factors such as the contractor, the size of your home, the extent of the damage and the ease of access (basement or crawlspace).  Since every job can be so unique, consider getting multiple quotes from local, licensed contractors for free at

According to Angie’s List, repairing a floor joist, most of the time, will be fairly straightforward.  During the inspection, a contractor will locate the broken joint and reinforce it by attaching a second joist next to it.  This type of repair, according to the experts and the article, will be in the $250 to $300 range.  However, if plumbing or electrical wire impede the repair, then the area could be reinforced with plywood, but it could come at a cost, often two times more than the prior mentioned method.

A structural engineer said you should be prepared to spend $7 to $10 per foot, depending on the working conditions and the amount of space the contractors have to work with.

What are the extra costs?

In some cases, floor joists can be damaged due to pests or water.  If pests were to blame, then you may need to consider calling in a pest control specialist.  On the other hand, if the damage were due to water, then you may need to call in a plumber or inspect to analyze the situation.

As mentioned, if there’s limited space, the subfloor will need to be replaced, which can increase the costs since the contractor will need to replace the subflooring.  The cost of repairing the subflooring will depend on the extent of the damage and how much subflooring needs to be replaced.  You will also need to consider the flooring once the subfloor is installed.

In rare circumstances, if the weight of the floor collapsed due to a heavy object, then you may need the assistance of a structural engineer to analyze the problem.

During the repair, as long as there’s access to a basement or crawl space, there won’t be significant damage done to your home.  However, if the access is limited, the subfloor will have to be removed, which can increase the costs.

Tips to know:

The Family Handyman shows you how structural repairs are made by “sistering” the floor joists.

Usually, a floor joist will measure 2″x8″, 2″x10″ or 2″x12″, and the size will depend on the load they are designed to carry, building codes and length.

How can I save money?

Get several estimates, especially if it’s a large job.  When requesting quotes, be sure to check reviews, references, insurance, licenses and be sure to receive an itemized quote.  While you don’t want to choose the cheapest price, you will want to choose the most experienced with the best value.

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