A.John Edgar, senior technical services manager at Sto Corp., a manufacturer of EIFS systems, responds: To fasten something light to an EIFS wall, you will need screws or lag bolts long enough to reach through the rigid foam to the sheathing or framing. You’ll also need a PVC sleeve (plastic tubing or conduit) with an interior diameter a little larger than the fastener. The sleeve allows the installer to tighten a screw against a solid object without crushing the EIFS.

Fastening an object through EIFS will be easier if the sheathing under the foam is plywood rather than gypsum. If the sheathing is plywood, use the following procedure: 1. Mark the location of the fastener on the finish. 2. Drill a hole through the EIFS up to — not through — the sheathing. 3. Line the hole with a neutral-cure caulk. (If the caulk smells like vinegar, it should not be used. A vinegar smell indicates an acid-cure caulk, which may corrode the fastener.) 4. Cut a length of your PVC sleeve about 1/8 inch longer than the thickness of the EIFS, and insert it into the hole. The sleeve should be 1/8 inch proud of the EIFS. Tool any excess caulk. 5. Fill the sleeve with additional caulk and immediately fasten the downspout through the fresh caulk in the sleeve. Remove any excess caulk.

If the sheathing is gypsum, the only locations where fastening is possible are at studs or blocking. Follow the same procedure described above. If it is necessary to fasten between studs, a toggle bolt may work. Of course, before drilling through any wall, be sure that there are no electric wires or gas lines in the area.