You’ve heard the term joist or floor joists and you want to know what it really means instead of *pretending like* you know what people are talking about. We got you.
At Anchor Foundation Repair, we work with floor joists all the time when it comes to house leveling and repairing your pier and beam or crawl space foundation. We have inspected and replaced thousands of linear feet of floor joists over our 35+ years in business in the Brazos Valley and can fill you in on floor joists.
This article will offer a definition and explain the purpose of floor joists in your pier and beam or block and base home. We will also discuss how you can tell if your floor joists are failing and how we typically fix them during the house leveling process.
Definition: What Is a Floor Joist?
A crawl space foundation is a complex wooden structure with layers of support and transition pieces that create the base of your home. The floor joists are one of the middle layers, located on top of the sill beams and underneath the subfloor.
Sure, you could look up the word joist in the dictionary, but we have crafted our own definition to talk about joists in a crawl space foundation specifically.
any of the smaller timbers arranged parallel to each other from wall to wall in a structure to support the floor
Floor joists span the space on top of the main sill beams in the structure of a crawl space foundation. They are placed parallel to one another but perpendicular to the main sills. The timber used for joists is:
- Most typical floor joist size is 2×6”
- Occasionally, 2×8” and 2 x10” joist timbers are used in homes
- Some well-built, engineered, custom homes might even have 2×12” floor joists
Joists are usually placed 16 inches apart on center. We sometimes encounter old homes where the joists were placed 22 to 24 inches apart and we have to add more joists because that spacing is just not strong enough to support the home.
Purpose: What Do Floor Joists Do In My Crawl Space Foundation?
Joists transfer the load vertically to distribute weight and evenly support the flooring system and everything else inside the home. Floor joists serve as a transition piece to allow for the installation of the subfloor and wall framing.
Problem Indicators: How Can I Tell if My Floor Joists are Failing?
Many things can go wrong in a crawl space foundation from settlement to wood rot to termites, or your piers could be degrading or moving. Each problem part tends to have a different feeling *under your feet* when they are failing and not functioning properly. For timber floor joists, the typical problem indicators are:
- Floors that feel like they might cave in, and
- The problem is more isolated to a small area and not an entire house or room
If you have a particular spot (or a couple of locations) in your house that feels like there is not enough support and could cave-in, but everything else seems okay, you might have a floor joist issue. Since many joists run throughout the home structure, just one broken joist will not cause a cave-in. But you should still get it addressed because there is likely something else going on besides just one broken joist.
Problems in crawl space homes tend to have a domino effect where one problem causes other problems. So it’s best to handle broken or compromised joists as soon as possible to avoid compounding issues.
Fixing Floor Joists During House Leveling
We rarely see just one problem with a crawl space foundation during house leveling. Usually, it’s not just the joists that are failing. But when we have to repair joists, here’s how we usually do it.
Joists are nailed or screwed into the subfloor and cannot be removed if damaged. So instead of removing damaged joists, we sandwich joists on either side of an existing (but failing) joist for more strength. The process is called “sistering” and it avoids damage to your subfloor because we don’t remove the damaged joist, we just add extra support on either side to provide the proper support.
If there are joist failures in addition to subfloor damage, then it’s a whole other approach. So if the subfloor is also a problem, then both the subfloor and the joists must be removed and fully replaced. This can only be done by cutting through your floors from inside the home to remove and replace the affected sections of the subflooring and joists.
How Can You Know For Sure What Is Wrong With Your Joists?
Now that you know what joists are *for real* you probably want to know if there’s anything else wrong. Do you have a foundation settlement problem or just some damaged joists? The best way to determine if you have a problem with your crawl space foundation is to get a foundation repair contractor to take a look at it with an inspection.
At Anchor Foundation Repair, we have been inspecting and repairing crawl space and slab foundations since 1985. We offer a free phone consultation as well as a paid In-Home Assessment to inspect your foundation and get you an estimate for repairs.
To figure out if your joist problem is connected to a greater foundation settlement problem, check out this article on the Top 3 Problem Signs for Your Pier and Beam Home’s Foundation next.