Drilling into concrete and masonry can be a disaster if you're not using the right tools. Here's some breakthrough advice on getting the job done right.
So here's a call I received once at the headquarters of MyFixitUpLife, where my wife Theresa and I offer insights into building, designing, and living through renovations as professionals and as a family. The call came from a friend who was having the darndest time trying to hang some shelves on a garage wall.
His was frustrated because the wall he was trying to drill into was made of concrete. Just as he'd seen me do on other projects, he picked up some masonry bits from the store for his cordless drill, but when he tried sinking holes in the wall the bits turned cherry red and left nary a mark on the concrete. He was at a loss and didn't know what to do.
The short answer is that drilling holes in concrete requires the right tools and bits. And, ironically, as they work together they don't "drill" in the same sense a wood bit does. What's happening when you use a concrete drill is that the tool and bit are pulverizing the concrete in front of the bit while the dust is getting pulled up and out of the hole by the flutes on the bit. This is why you'll see the term "hammer" on a tool that drills holes in concrete and masonry -- because hammering is what it's really doing.
There are two types of hammers for drilling concrete: A hammerdrill is for drilling small holes (roughly a half-inch or less) and a rotary hammer is for drilling large holes (roughly larger than a half-inch, depending on the tool). And while the rotary hammer, which is a professional tool, can also drill small holes, a hammerdrill can't drill large ones, so it's important to buy or rent the right tool for the job.
When people ask me to give a list of the five essential tools to have around the house or shop, an 18-volt drill/hammerdrill almost always makes the short list. All the majors make them (here's a Porter-Cable model at left as an example) and they're ideal for drilling small holes for small expansion anchors -- what some people call "moly bolts."
Drill in moly bolts for light-duty connections to concrete and masonry -- everything from hanging vinyl shutters from a stucco house to attaching metal shelf brackets to a concrete or block wall. We've had good performance over the years with Red Head Poly-Set anchors for chores like this. We've even had great luck using hammerdrills on plaster-on-block walls that are as hard as concrete.
NOTE: If your plaster is over lath (a thin, narrow strip of wood; knock, and if it sounds hollow and/or doesn't break your knuckle it's probably over lath), try drilling first in non-percussion mode with a hammerdrill bit to see if the bit will drill out the plaster. Using the drill in hammer (percussion) mode might blow out the plaster because there's nothing behind it but air.
What's particularly efficient about using a drill/hammerdrill is that you can use the same tool to drill the anchor hole, then drive the anchor (in this case a screw). Drill/hammerdrills are also a good go-to for drilling holes in concrete floors for metal thresholds.
The tool's impact mechanism (called a "gubbins" for tool geeks like me) works like two poker chips spinning against each other, causing vibration at high speeds. This tool isn't for all-day drilling and driving by any means, but it'll get the job done for smaller projects like hanging a light fixture on a brick house. The tool vibrates quite a bit and the sound it makes is pretty loud. The hole goes down, but you know the tool's working -- and so do your neighbors.
The rotary hammer is the Rolls Royce of the concrete-drilling world. Oversimplifying it somewhat, they work like jackhammers. A piston drives the bit forward which pulverizes the concrete or stone in front of it more effectively and much more quietly than a hammerdrill. As a result, you can work faster and drill significantly larger holes with these tools.
While we'd recommend renting them for most homeowners because they're both specialized and expensive tools (with their own dedicated and expensive bits) they are the go-to implement if you have to drill half-inch or larger holes. Say, for example, you're building a deck on a stone house or drilling a hole for a dryer vent in a block house. Rotary hammers come in many sizes from small to mondo so when you rent one make sure to tell the rental salesman exactly what you're doing so he can select the right hammer for you. At MyFixitUpLife headquarters, we've had good luck on the smaller end of the weight scale - about 12 pounds - for most of the concrete drilling we do on our professional job sites.
Some rotary hammers also come with a chipping function (again, think handheld jackhammer here). The effectiveness of this is commensurate with the size of the hammer you're using, but if you have to chip concrete for some reason - maybe for eliminating an old clothesline footing, an obsolete planter, or blob of concrete ancoring a fence post - you can break the concrete up using this tool.
So whether you plan to hang shelves or build a deck, whenever you come across concrete, the shortest path to success is using the right combination of bits and tools to get the job done right.
Mark Clement is a contractor and all-around DIY pro. See more of his advice and projects at MyFixItUpLife.com.
Here are some more tips from DIY Life about choosing the right drill:
In The Workshop: Cordless Drills
In The Workshop: Drill Bits
Drilling Masonry: Avoid Disaster with the Right Tools
Want to know more? Check out this video on drilling: