Mouse fence keeps rodents out of vehicles

By Mark Stromberg

Rodents are notorious for infesting vehicles. Some will build nests in the shelter of the engine compartment, while others prefer to gnaw on wiring insulation or to drink sweet-tasting antifreeze. Species ranging from field mice to wood rats and even marmots have all been known to wreak havoc on car electrical and cooling systems. The problem is particularly severe in rural areas, where leaving a vehicle outdoors overnight can leave a driver stranded.

Over decades of living in rural Carmel Valley as director of the UC Nature’s Hastings Natural History Reservation, I used a practical and relatively inexpensive solution to protect my vehicles: a mouse fence. The fence was inspired by a structure originally devised by Feynner Arias, then reserve steward at the UC Nature’s Landels-Hill Big Creek Reserve in Big Sur. Our approach takes advantage of the fact that mice and rats prefer to run alongside a wall rather than climb over it. As long as the wall is higher than the body length of the rodent, rodents will go around rather than over.

The barrier itself consists of aluminum flashing. Flashing can be bought in rolls from roofing suppliers and most hardware stores. Both 10”- and 12”-wide flashing will keep rodents out. Consider whether the doors of your vehicle will clear the top of the flashing size you choose when the doors are opened.

Laying out your corral

As you plan the dimensions of the corral, be sure to make it wide enough to fully open the door if your vehicle’s door can’t clear 10” flashing. The wider you make the exclosure, the easier it will be to open the car door. Buy enough 2’ x 6’ lumber pieces to go around the entire perimeter of the corral; these will serve as the wall supports. Because these wood pieces will lie on the ground, select either pressure treated wood or rot-resistant redwood.

Cut a groove along the long axis of the 2’ x 6’s to hold the flashing. Either a table saw or a router would work. A router can be more convenient to make a curved groove around the corners.

Hammer small finish nails at a 45-degree angle through the bottom of the upright flashing and into the wood. Seal the bottom with caulking if you like.

Place the flashing

Slide the flashing into the groove, and overlap the flashing panels inside the fixed sides. When placed in the right arrangement, the flashing groove around the corner on the end panel should line up with the flashing groove on the long side panels. Slide a section of curved flashing into the groove around the corner from a long side to the back side.

At the front of the exclosure, which doesn’t open, bend the flashing around the corner and nail it into the wood. A groove around the corner in the wood support holds the flashing in place. The 2’ x 6’ wood pieces are connected with steel straps screwed into the corner. Bend the flashing to fit the corner.

Adjusting the rear wall

The wall at the rear can be opened, enabling you to move the vehicle in and out. Use clips that can be unfastened to connect the tops of the flashing panels along the longer sides of the vehicle. Overlap the panels inside the fixed sides.

The rear panel lays flat on the ground. Kick gravel along the bottom to hold it in place.

To provide stability in wind, screw shelf brackets into the wood. Thread a loop of wire at the top of the bracket through the flashing. The slight bend in the top of the flashing forms a kind of running wiggle that makes the flashing more rigid in wind.

Connect the pieces of lumber used to support the wall with metal straps used for framing construction. Screw the straps into the flat 2′ x 6′ on the ground.

To move the vehicle, move the rear wall out of the way. Do this by removing both the shorter sections of flashing that form the corners, then picking up one end of the board (with flashing) and rotating it out of the way.

If your parking place isn’t level, you can use gravel as an underlayment to fill any gaps beneath the wood supports.

A wall constructed with stake supports

Stakes are an alternative way to hold the barrier in place. Stakes can be used to both support the flashing and fasten the exclosure to the ground.

For more information about this rodent wall, contact the author at [email protected]