Finding a snake under a concrete slab, porch, or slab-on-grade addition is a common report in Western North Carolina, particularly during the warmer months. The gap between a concrete slab and the ground beneath it is almost perfectly suited to snake thermoregulation, cool, dark, stable in temperature, and often accessible to rodents. Understanding why snakes use these spaces makes it easier to decide what to do about them.
Why Snakes Use Slabs and Porch Undersides
The void beneath a concrete slab maintains a relatively stable temperature year-round, cooler than the surface in summer, warmer than the open air in winter. Snakes, which regulate body temperature through their environment, seek exactly these conditions. The transition zone between direct sunlight and a cool, shaded void is a preferred basking location for many species, including copperheads and rat snakes.
Rodents also use these same voids. Mice and voles tunnel under slabs in search of insulated denning sites, and snakes follow their prey. Finding a snake under a slab is often a strong indicator that rodent activity is also present in the same space.
Common Species Found Under Slabs in WNC
- Eastern black rat snake: Most common large snake in the region. Benefits the homeowner by controlling rodents. Non-venomous.
- Northern copperhead: Venomous. Common in rocky and wooded mountain terrain. Present under slabs on properties near wooded lots or rock outcroppings.
- Eastern garter snake: Small, striped, non-venomous. Very common around foundations and moist areas.
What Actually Addresses the Situation
Removing a snake from under a slab does not prevent the next one from using the same space, because the habitat conditions that attracted it remain unchanged. The more effective approach is to reduce what draws snakes to the area:
- Address rodent activity in the void beneath the slab.
- Install a buried wire mesh apron around the perimeter of the slab to block rodent tunneling access.
- Reduce harborage adjacent to the slab, wood piles, stone walls, and dense ground cover directly adjacent to the concrete.
- Seal any foundation gaps that allow snakes to move from the slab void into the crawlspace or basement.
A venomous snake observed repeatedly in the same location near a structure is a situation that warrants professional assessment, not to harm the snake, but to understand what is drawing it there and whether exclusion measures are warranted.
