Northern Prairie Wildlife Research Center
An especially difficult challenge has been that of excluding bats, particularly
the Mexican free-tailed bat, from roosting under Spanish or concrete tile
Bats often roost under the tiles by entering the open ends at the lowermost row or where the tiles overlap. The bats enter the openings by landing on or just under the edge that is directly under the open tiles. Where bats enter the sides of the tiles which overlap building walls, they have to land on the wall before crawling inside.
Attempts to prevent the bats from entering the spaces have included plugs made of various materials and shaped to fit the openings. These were ineffective because tight-fitting plugs were impossible to fashion due to variation in size of the openings and temperature changes. Daily temperature fluctuations also caused the tiles to break by contraction and expansion, thus leaving spaces through which the bats could enter.
Constantine (1979a) found a solution to the above problem in California when tiles were temporarily removed to replace a layer of tarpaper under the tiles. A layer of coarse fiberglass batting was laid over the tarpaper and under the tiles so that bats entering the holes would contact the fiberglass and be repelled. To prevent birds from using fibers for nest making, the coarse fiberglass batting was applied within 15.2 cm (6 in.) of the outer opening of the open tile ends. Although this solution has been effective, it is only practical to remove the tiles when tarpaper has to be replaced.
Constantine (1979a) also found that bats may be excluded from the tiles if rain gutters are installed directly under the open tile ends as well as under the overlapping tiles. The upper edge of the gutter should be level with the lower edge of the tile and should extend outward about 20.3 cm (8 in.) from the tile. The gutter must be tightly fastened flush with the wall to avoid leaving a dark slot that bats may occupy. Another problem occurs when rain gutter installations leave an open space or passage between the gutter and the tiles where bats crawl into the tile openings after landing on the wall. In some instances, flashing material extending upward under the overlapped tiles may be sufficient.
Gaps under corrugated and galvanized roofing and sheeting may be sealed by a self-expanding urethane foam previously mentioned. In Britain, fiberglass and resin have been used in situations where corrugated hanging tiles, roofing, or weatherboarding shift in heating and cooling situations. The fiberglass can be dyed almost any color to match wood or tiles (Fig 17). In some situations, fine mesh, about 0.63-cm (1/4-in.) diameter holes, has been spread over wood or tiles, and then painted to match the underlying material (R.E. Stebbings, personal communication).
|Fig. 17. Gaps under corrugated and galvanized roofing may be sealed with a self-expanding urethane foam, fiberglass, and resin. (By J. Newel Lewis. Dip. Arch., F.R.I.B.A.Trinidad and Tobago)|