They remove support, they don't chew concrete
Iguanas don't gnaw through concrete or block. What they do is quietly remove the support underneath it. A burrow dug against a foundation, slab, or footer hollows out the compacted soil the concrete was poured to bear on. Concrete is strong in compression but has almost no ability to span an unsupported gap, so once the soil under a spot is gone, that spot has nothing to rest on.
On a typical South Florida property the burrows start where the digging is easiest: a planting bed against the house, the soft edge of a driveway, the swale, or the backfill along a pool deck. From that soft entry point the tunnel runs underneath the hardscape, sometimes several feet.
How it shows up
The damage announces itself as settling. You'll see stair-step or diagonal cracks, a section of slab that sounds hollow when you tap it, a slab edge that has dropped a step below the rest, or doors and screen tracks that suddenly bind because a corner has moved.
- Hollow-sounding concrete when tapped over a suspected void
- Cracks that follow the line of a burrow rather than a control joint
- A dropped lip at a slab edge or joint — a classic trip hazard
- New gaps opening between a slab and the wall it abuts
A slow problem until it isn't
A single burrow rarely threatens a house foundation, which is usually deep enough to shrug off one tunnel. The real concern is repeated, expanding burrowing in the same area over months — especially where a female returns to the same nesting spot season after season and enlarges the network each time.
The economics are lopsided. Catching it while it's still small voids and hairline cracks means filling and compacting soil for very little. Waiting until a slab has cracked or dropped means demolition, re-compaction, and a new pour.
What's most at risk
Lightweight, shallow-bearing structures fail first: pool decks, driveways, sidewalks, paver patios, and A/C condenser pads all sit on relatively thin soil and settle long before a house footer moves. Those are the structures to inspect first when you find burrows.
Common questions
Will an iguana burrow crack my house foundation?
A house footer is usually deep enough to resist a single burrow, but repeated burrowing that hollows the supporting soil can cause settling and cracks over time, so it is worth addressing early rather than assuming the slab is safe.
What's most at risk from burrowing?
Slabs and lightweight structures. Pool decks, driveways, sidewalks, paver patios, and A/C pads settle first because they sit on shallow soil that a burrow easily undermines, while a deep house footer is far more forgiving.
How can I tell a void has formed before the concrete cracks?
Tap the slab — a hollow, drum-like sound over one area suggests the soil beneath has washed out. Soft or sunken turf beside the slab edge and a fresh burrow opening nearby are the other early clues to look for.
