How Do I Know If My Floors Are Sagging Because of Termites?

You’ve been noticing it for a little while now, maybe a spot in the hallway that feels softer than it used to, or a section of floor near the bathroom that has a little give when you walk across it, or you can actually see a slight dip in a room that used to be flat. You’ve been telling yourself it’s nothing, or that it’s just the house settling, but it keeps nagging at you. And now that you know termites have been in the house, or you’re wondering if they are, the question is whether that floor is related.

Sagging floors have a few possible causes, termites being one of them

The reason this is hard to sort out on your own is that a floor that sags or feels soft can come from a few different things. Moisture damage and wood rot can cause the same kind of softness termites cause, because both involve wood breaking down and losing its ability to hold weight. Old homes sometimes have floor joists that have just worn down over decades. And termites, specifically subterranean termites which are the most common type around here, go after floor joists, sill plates, and the structural wood that sits closest to the ground because that wood is closest to the soil where they live.

What subterranean termites actually do under your floor

Subterranean termites come up from the soil, which means the wood they hit first is whatever’s closest to the ground, your foundation sill plate, the floor joists that run across the crawl space or sit on the slab, and the subfloor on top of those joists. They eat along the grain of the wood, hollowing it out from the inside while the surface can still look mostly intact. So a floor joist that looks fine from a quick glance underneath might already be significantly weakened. The floor above it starts to feel soft or sag as that joist loses its ability to hold up under the weight of the floor and everything on it.

Does a soft spot always mean structural damage?

Not always, but it’s not something to brush off either. A soft spot right near a toilet or under a sink is often moisture related, since those areas tend to have small leaks that go unnoticed for a while and rot out the subfloor over time. That’s still a repair but it’s a different cause. A soft spot in the middle of a room, away from any plumbing, or one that covers a wider area rather than just one small spot, is more likely to involve the joists or framing underneath rather than just the surface layer of subfloor. Termite damage tends to affect a wider run of wood rather than one isolated soft patch.

How do you actually check underneath?

If you have a crawl space, getting under there with a good flashlight is the most direct way to see what’s going on. You’re looking for mud tubes running up from the soil to the wood, which are the little brown tunnels subterranean termites build to travel without being exposed. You’re also looking for wood that looks darker than it should, feels soft when you press on it, or sounds hollow when you tap it. A screwdriver test works here too, if it sinks into a joist without much resistance, that wood has been compromised. If you’ve got a slab foundation with no crawl space access, this is harder to assess without pulling up flooring.

What about houses on a slab?

Termites can still get into the structure of a slab home, they just come in through different routes, usually through expansion joints, utility penetrations, or cracks in the slab itself. In a slab home, sagging floors are less likely to be termite related since there aren’t exposed joists sitting over soil, but it’s not impossible, especially if termites have been active in interior walls or around the perimeter where wood framing meets the slab. If you’ve confirmed termite activity in a slab home and your floors feel off, it’s worth having someone check the wall framing and door openings near the affected area.

Can a sagging floor be fixed or does it have to be replaced?

It depends on how far the damage goes. If a joist is damaged but the wood on either side of the damaged section is still solid, sometimes a new piece of lumber can be sistered alongside it, meaning bolted right next to it to take over the load. That’s less invasive than pulling everything out. If the damage is more extensive and multiple joists are affected, or the sill plate itself has been compromised, the repair gets bigger. The subfloor on top sometimes has to come up to properly access and replace the framing underneath, which means flooring on top of that has to come up too.

What’s the first step if you think this is what’s going on?

Getting eyes on the actual framing is the only way to know what you’re dealing with. A soft floor tells you something is wrong, but it doesn’t tell you how much of the structure underneath is involved or whether it’s termites, moisture, or both. Those things matter for figuring out what the repair actually looks like and what it’s going to take to fix it properly. Guessing at the repair without knowing what’s underneath tends to lead to fixing the surface while leaving the real problem untouched.

If your floors are feeling soft or showing a sag and you’ve had termite activity in the house, our termite damage inspection and floor repair service can get under there and figure out what’s actually going on with the framing, so you know exactly what needs to be fixed and why.