Mice in Adobe and Stucco Homes: Finding and Closing the Gaps

Mice get into Albuquerque's stucco and adobe houses low and quietly: along the bottom edge of the stucco, around pipes and cables, under door thresholds, at old window frames and where an addition meets the original wall. Close everything over a quarter inch with metal, mesh or mortar and most problems stop.

The finishes that make local houses look the way they do also make gaps easy to miss. A crack in earth-toned stucco blends right in. Here's where to look on the three wall types you'll find around town.

Most houses built since the 1950s, from the Northeast Heights to new builds in Mesa del Sol, are wood frame with a stucco skin. At the bottom of the wall, the stucco ends at a metal strip just above the slab. That line can open into a gap as the house settles or the soil shifts, and mice follow it into the wall cavity.

Cracks that run up from corners of windows and doors are mostly cosmetic, but a crack that opens at the base or around a pipe is an entry point. Check those first.

Older homes in Nob Hill, the South Valley and parts of Belen include adobe and other masonry. Thick walls don't stop mice if there's a path around them. The weak points are where wood meets earth or masonry: window and door frames, roof beams that pass through the wall, and seams where newer frame additions butt into old walls. Patches from decades of repairs don't always bond.

Sealing an old house takes care. Ask the provider what materials they'll use and how they'll match the existing finish.

Concrete block is common in garden walls and some houses. The hollow cores connect along a wall, so a mouse that gets into one gap can travel. Block walls around yards also give mice and pack rats a sheltered route from lot to lot. Where a garden wall meets the house, there's often a gap at the joint.

Walk the outside with a flashlight and look for:

• Gaps at the base of the stucco, along the slab
• Openings around gas, water, AC, cable and phone lines
• Worn door thresholds and missing sweeps
• Gaps around old window frames
• Joints where additions, garden walls or porches meet the house
• Vents with torn or missing screens
• Swamp cooler ducts where they pass through the roof

NMSU Extension says mice fit through holes about a quarter inch wide and recommends quarter-inch hardware cloth over openings. It warns against steel wool, latex, plastic, rubber and wood. The state rodent guide lists cement, concrete, galvanized sheet metal and hardware cloth as gnaw-resistant, and calls plastic, wood, rubber, vinyl and foam easy to chew.

On the wall itself: pack mesh into the gap, then cover it with mortar or a sealant that matches the wall. Use metal flashing at the base of the stucco where the gap is long. A provider who works on older homes will know how to keep it neat. See rodent exclusion.

Trap first, then seal, so nothing gets closed in a wall. If you hear them at night, mice in walls and ceilings explains how providers handle wall voids without cutting into plaster.

Most entries are low, but mice and pack rats also climb. Rough stucco, vines and block walls give them a route to the roof. Once there, gaps at parapet caps, vent pipes and roof-mounted coolers lead into the ceiling cavity. If you hear activity overhead rather than in the walls, have the roofline checked. See attic cleanup and roof sealing.

Plants and stored things against the house give mice cover right at the gaps. The state rodent guide suggests trimming plants 3 to 4 feet back from buildings and keeping a clean, weed-free strip about 3 feet wide along the foundation, either mowed or covered with crushed rock. Move firewood to a rack 18 inches off the ground and away from the wall.

Ask how they'll seal at the base of the stucco, what they'll use around utility lines, whether they'll check the roofline and how they'll match the finish on an older house. Ask for photos of each spot they sealed. A provider who works around Albuquerque should be comfortable with stucco, adobe and block. See rodent exclusion for more.

A provider who only offers to spray foam into cracks is not doing exclusion work, so keep looking.

• When the Nights Turn Cold: Getting Ahead of Fall Mice
• Saw One Mouse? Here's How to Tell If It's Alone
• Mice in Mobile and Manufactured Homes
• What Rodent Control Costs Around Albuquerque

Services: Sealing and Exclusion / Mice in Walls and Ceilings / Rodent Inspection

1. NMSU Extension Guide L-209: Rodent Control and Protection from Hantavirus
2. New Mexico Department of Health: Domestic Rats and Mice