Drilling Into Stucco
DEAR TIM: My home is made from stucco and I would really like to hang some decorative art objects on the exterior walls. I am having big problems trying to figure out to drill holes into the stucco so as not to damage it. Is it safe to drill into the stucco? Will it cause leaks that can lead to mold? Kristine N., Victorville, CA
DEAR KRISTINA: I think your idea is a splendid one and often wonder why more people don't hang things on their houses. I can understand why someone would not want to drill a hole into a brick or into a decorative stone, but even these things can be cleverly patched with a moderate amount of skill. As soon as you get the tool and a few inexpensive pieces of hardware you need, your house is going to be the best looking on the street. You will have those pieces of art securely fastened in no time.
The first thing you need to determine is the type of stucco you have on your home. Over the past 20 years, a synthetic stucco has been used that too many homeowners think is traditional cement-based stucco. The synthetic stucco is called Exterior Insulation Finishing System or EIFS for short. Most of these systems consist of factory-made acrylic-based products that are applied out of buckets. They are often applied over a layer of foam insulation.
Traditional cement stucco plaster is just that. It is a mixture of sand, Portland cement and sometimes some hydrated lime. Once dry, it is as hard as rock because it is actually man-made rock. Cement stucco is much harder than EIFS and it rarely is applied over insulating foam. Cement stucco is typically applied over regular wall sheathing that is covered with tar paper or some other water barrier which is covered with a wire mesh to give the cement stucco great strength.
If your home is covered with EIFS, you must contact the manufacturer of the system to get their explicit written instructions as to how to drill and seal the hole. If you do not perform each step as outlined, you can void the warranty on the EIFS system. This is very important as many of the EIFS manufacturers have been involved in mold-related cases that stem from water getting into and behind these exterior skins.
Traditional cement stucco is easy to work with and drilling into it is simple if you have the right tool. I have successfully used a hammer drill with a 1/4 inch bit to drill holes into stucco. Hammer drills can be rented at tool rental businesses. You can also buy a handy cordless model for several hundred dollars or less. You will also need to get a 1/4 inch anchor kit that has plastic anchors in it with matching screws. These kits are readily available at any hardware store.
Once the hole is drilled, carefully blow out any dust. Use a turkey baster or compressed air to do this, not your mouth as dust may shoot back and get in your eyes. Once the hole is dust-free, squirt a small amount of acrylic caulk into the hole. Then insert a plastic anchor and tap it snugly into the hole.
I would then use a stainless steel screw instead of the ones that came with the anchor kit. The hardware store should have stainless steel screws that are the exact same size as the ones in the kit. Stainless steel will not rust over time.
Cement stucco will support a tremendous amount of weight because you are basically drilling into rock. But if you are hanging heavy objects on an EIFS system, you may run into problems. The thin acrylic skin is not structural nor is the foam beneath it. You may think your art work is fine, but over time the anchor holes can enlarge and water may get into the walls. Be very careful hanging any objects on an EIFS system.
Drilling into cement stucco with a hammer drill is like using a regular wood bit and drilling into balsa wood. A hammer drill acts like a miniature jack hammer and pounds the hard surface as the drill bit spins. Even with this seemingly destructive action, the hole that is drilled is extremely precise.
Always make sure you drill only as deep as necessary. Pay attention to the length of the anchor and screw and only drill 1/8 inch deeper than the screw is long. Be very careful around areas where you think electric wires or water lines might be present.