Drywood and subterranean termites spread at very different speeds — and 'slow' doesn't mean 'safe.' Here's how fast damage actually accumulates.
When people ask how fast termites spread, they're usually trying to gauge how worried to be — is this a this-year problem or a this-decade problem? The honest answer is that it depends heavily on the species, and that "slow" is not the same as "safe." Here's how the two types that matter in Southern California actually spread.
Drywood Termites: Slow but Persistent
Drywood colonies grow slowly. A new colony started by a pair of swarmers is tiny for its first few years and adds members gradually, which is why it can take three to eight years before there's enough activity to produce visible frass or a swarm. So in any given month, a single drywood colony isn't doing dramatic damage.
The catch is time and numbers. That slow colony feeds continuously for years, and a home can host multiple independent drywood colonies at once — one in the fascia, another in the attic, another in a window frame — since they don't need to be connected. Slow, multiplied by years, multiplied by several colonies, adds up to real structural damage.
Subterranean Termites: Faster and Larger
Subterranean termites are the faster, more aggressive story. Their colonies grow much larger than drywood colonies — often into the hundreds of thousands — and they forage over a wider area through mud tubes, hitting multiple points of a structure from a single ground nest. Where conditions are favorable (sustained moisture), they can do noticeable structural damage faster than drywood termites. Our post on how subterranean termites destroy homes covers how that foraging works.
How Fast Does the Damage Add Up?
| Drywood | Subterranean | |
|---|---|---|
| Colony growth | Slow (years to mature) | Faster, much larger colonies |
| Typical location | Above-grade wood, attic, eaves | Ground contact, then upward |
| Speed of damage | Gradual, compounding over years | Can be faster where moisture supports it |
| Common complication | Multiple independent colonies | Wide foraging from one nest |
The practical takeaway is that neither is a "deal with it later" problem. Drywood is slow but relentless and often plural; subterranean can move faster than people expect. In both cases the damage curve only goes one direction.
Why "Slow" Still Means "Act Now"
The reason slow doesn't mean safe is that termites are usually found *years* into their run, not at the start — so by the time you know, the clock has already been running. Every month of "I'll get to it" is added onto however long the colony was working before you noticed. The cheapest point to treat is always as early as possible, which is what an inspection establishes — see termite damage and repair costs for how scope drives the number.
A free inspection tells you which species you have, how far it's spread, and therefore how urgent it actually is.