My first encounter with construction lasers was 20-plus years ago on a commercial job site, where a subcontractor was using a rotary laser to level the track for a suspended ceiling. The tool obviously saved a lot of time, and even though it could only shoot level, I was jealous that my company couldn't afford the $3,000 it cost to buy one. Since that time, lasers have fallen greatly in price and become much more versatile. I now own several and can't imagine trying to compete without them.
For this article, my crew and I tested a type of line laser that didn't exist until several years back. The industry hasn't created a name for these tools; I like to think of them as combination lasers, because they combine the functions of a cross-line laser with those of a plumb bob: They project visible plumb and level lines, and plumb points up and down. With the right combination laser, a contractor may be able to perform all of his leveling and layout tasks with a single tool.
We tested nine combination lasers, one from each of the companies (two from Topcon) that currently make them: the Agatec CPL 50, Bosch GLL3-80, Hilti PMC 46, Johnson 40-6662, Leica Lino L2P5, Pacific Laser Systems (PLS) HVL 100, Spectra Precision 5.2XL, Topcon LC-2, and Topcon LC-4X.
Laser models change quickly, so there may be additional ones on the market by the time this story comes out.
All the lasers we tested perform the standard functions of line lasers – projecting horizontal lines that can be used to level deck ledgers, windows, and cabinets; and vertical lines that can be used to plumb door casings, posts, and the like. The lines meet at a 90-degree angle and can be used to project square layout onto plumb surfaces like walls. On a number of models, the beams fan out far enough to project square layout across the floor, up the wall, and onto the ceiling.
Among the qualities that set combination models apart from standard line lasers is their ability to project points straight up and down, so that they can be used in place of a plumb bob. A combination laser is faster and easier to use than a plumb bob; it can be operated by one person and is unaffected by wind. The plumb points appear as single laser dots or as the intersections between laser lines above and below the device. We use the plumb bob function to locate can lights – we lay out their locations on the floor and then carry those marks up to the ceiling. When framing, we use it to plumb walls by checking the alignment of top plates over bottom plates.
With most models, the self-leveling function can be disabled so that the tool can project sloped lines and square layout that isn't plumb or level. This function comes in handy for tasks like laying out stair rails and setting wall tile on the diagonal.
All of these tools are self-leveling. Most rely on a pendulum hung from gimbals, using gravity to bring the device to level in a second or two. The exception is the PLS HVL 100, which relies on a pair of servo motors; they take longer (about four seconds) to level the tool but are better able to maintain a steady line when foot traffic or power equipment is shaking the floor. Servo motors are typically found in rotary models; it's unusual to see them in a line laser. Lasers with servo motors are best for applications where the tool is left in the same location for a period of time. Pendulum models are better when you need to level or plumb something quickly and then move on.
A laser's internal mechanism is delicate and must be protected against shock damage. This is usually achieved by means of a manually activated lock, which prevents the pendulum from swinging around when the tool is transported. A couple of models don't have locks: Hilti's pendulum is protected by rubber padding inside the housing, and the PLS laser doesn't require a lock because its mechanism is held in position by a spring and the two servo motors.
Typically, a laser must be placed within 3 to 5 degrees of level for it to level itself. If the tool can't come to level, it will send out an audible beep, turn the beams off, or flash the beams. This function is important because otherwise you might accidentally use lines that aren't level or plumb.
The usual way to project sloped lines is by using the laser with the pendulum in the locked position. When operated this way, the tool will remind you that it's not level by flashing the beams or by flashing or illuminating an indicator lamp. Flashing beams are better because they're impossible to miss; you might not notice the indicator lamp. If the tool does rely on an indicator, it's a good idea to check every now and again to make sure that the laser is set the way it's supposed to be.
Like other line lasers, combination lasers have far less range than rotary models. The line from a rotary laser is a focused beam of light being spun in a 360-degree arc; a line laser's beam is more diffuse because it has passed through a lens that spreads it into a continuous line. It's like the beam on a flashlight – it becomes dimmer as it covers more area.
The range of these tools is listed in the spec tables. When used indoors, the range is highly dependent on the ambient lighting conditions: The brighter the surroundings, the harder it will be to see the line. Past a certain point, the line won't be visible to the naked eye – and then you'll have to use a target card, laser glasses, or a receiver to locate it. I find that I rarely need to use receivers indoors, because the lighting is dim and the distances are short enough to make out the beam. But outdoors, and especially over greater distances, the only way to detect the beam is with a receiver, which produces an audible beep or displays an icon on the screen to indicate that a beam is hitting it.
Receivers work only with models equipped with a pulse function. When the laser is set to pulse, the beam flicks on and off very rapidly – so rapidly it can only be detected by the receiver. In my experience, receivers are interchangeable within brands and usually between brands. This was the case with all but three of the tools we tested: The Agatec and Topcon LC-2 work with a receiver that doesn't work with other lasers, and the Bosch did not work with any of the receivers we had – though it does work with one from Bosch. If you need a receiver, it will be less expensive to buy it as part of the kit than to purchase it separately.