"Tool Test: Laser Levels"

By Steve Veroneau

Self-leveling rotating levels can make shooting grade or transferring layouts a single-handed breeze. We field-tested nine new models that cost less than $2,000.

As a residential framing and finish contractor, I'm always looking for new tools that help me work faster and deliver better product to my clients. My company's projects are usually large-scale, complex residential remodels with multiple elevation changes. We often wrap trim details around rooms to tie door and window heads together.

Using a laser level to set these critical layout points is the way to go; it saves time over manually chalking level lines or setting up a traditional transit. For several years I've used a vial-calibrated laser level, which produces a dot. It's a fine, accurate tool, but it requires two people to operate it efficiently -- or one person who does a lot of walking.

Self-leveling rotating laser levels are the next evolution: Their quick set-up, accuracy, and efficient one-person operation make their steep price tags worth the money. Many builders find these tools quickly pay for themselves in man-hours saved.

My carpenters and I tested the CST/Berger 57-LM400-1, David White 4110-1 AutoLaser 2110, Laserjamb Q-Pro Multi-Line, LCI Lasers 621-R Auto, Laser Reference Pro Shot L5, Stabila 05100, TLZ. RoboLaser (RT-7210-1), Trimble (formerly Spectra Precision) Spectra Lasers 1452XL, and Topcon RL-VH3C.

Except for the Laser Reference and TLZ. models (which cost $750 and $300, respectively), these tools cost between $1,445 and $2,000. For that kind of money, I wanted to evaluate the bang for the bucks. Do these tools really self-level? How sensitive are they? Can I give the tool to a lead carpenter and expect him and his crew to use it with a reasonable learning curve? Does the tool do what the manufacturer says it will? What are these tools' limitations?

Test Criteria

First I shop-tested all the tools for ease of set-up, interior and exterior use, beam visibility, and accuracy, and evaluated base package accessories like remote readers and remote controls. I then sent the tools to the field to check for level on new foundations, set grades, and to find level lines while tying new work into an old, sagging house. After my crew had handled the lasers with all the delicacy one would expect from field carpenters, I re-tested them all for accuracy and consistency at varying distances.

Setup and Operation

Getting Level. All the tools I tested are ready to go right out of the box. Each comes with a screw mount that attaches to any tripod -- which all manufacturers offer as optional accessories. Once you mount the unit on a tripod, you turn it on and wait a few seconds while it self-levels. The red laser beam usually blinks and steadies itself after the leveling function is complete.

These tools use various internal mechanisms to level themselves. The TLZ. laser employs a pendulum, the Laser Reference model uses a wire-hung, air-dampened compensator, and the rest use electronically driven servo motors. I couldn't detect any significant leveling time difference between the systems.

Controls. The Trimble level was the easiest to operate. I really like its remote control and appreciate its simple control panel. It has few buttons but plenty of functions. The well-designed laser eye control allowed me to adjust the reading sensitivity for my needs. Topcon's tool is an exceptional level, too, although it performs more functions than I usually need on my residential jobsites. It seems best suited for users who do lots of slope work. The remote control makes it really easy to manipulate the X and Y axes for this application only. Because I don't use that feature in my work, I found the tool's controls a little too busy.

I found Stabila's, LCI's, and TLZ.'s remote control/control panel configurations versatile and easy to use. Stabila's well-designed remote let us switch between the different beam functions from a distance. LCI's remote adjusts the spin rate; chalkline or dot adjustments are keyed into the tool. TLZ.'s straightforward remote also gives you good tool control from a distance. It activates the level and lets you rotate the beam right or left at fast, medium, or slow speeds so you can hit your mark quickly.

The Laser Reference remote control turns the level on and off and doubles as a remote reader. The David White tool comes with a remote reader but no remote control for the unit itself. Since the tool is on constant spin, the remote reader is a necessity.

Accuracy. We used the levels to lay out a foundation, set grade and wall heights, and verify an old, existing house's conditions while tying in an addition. We also set door and window heights on another addition. For each task, we used the CST/Berger, Laser Reference, LCI, Stabila, and Trimble levels which have three modes: dot, chalkline, or continuous rotation. Each worked very well. We found that the Laser Reference, and Laserjamb models don't allow for a single-dot function. The constant-spin David White tool produces neither a dot nor a chalkline, and the TLZ. level only produces a dot. With the exception of the TLZ. and David White model, which only work on a horizontal plane, all of these tools let you set vertical and horizontal lines. They're all accurate to within 1/4-inch over 100 feet or better. I staged a control test to see if they stayed that way after life on the job.

First I struck lines at 20, 40, 80, and 120 feet with all the tools before they went to my jobsites. After they returned from the field, we tried to get the tools to hit the same marks I'd struck earlier. After weeks in the field, all the lasers stayed within their published margins of error (see spec boxes). While I wouldn't treat them like my framing nailers, all of the lasers showed some grit during our test.

Adjustments. The LCI, Laser Reference, CST/Berger, Laserjamb, and TLZ. models let you adjust the X and Y axes with adjustment screws. The other models require adjustments by certified professionals. With the exception of the TLZ. model, all the levels we tested include functions for squaring rooms, walls, and foundations. All let you set slopes, too. They all turn off if they get knocked out of level.

Seeing the Light

Accessories. Since lasers are nearly impossible to see in direct sunlight, it's important that manufacturers include accessories -- particularly remote laser readers -- in the tools' base packages.

These tools can be very specialized. Manufacturers offer various packages for numerous trades and applications, including suspended ceiling installation and electrical work. Despite these tools' sophisticated, expensive technology, they're very limited without the right props.

Laserjamb recognizes the need for versatile jobsite accessories. Its easy-to-use tool mounts on a tripod or the company's adjustable pole and includes a reader and remote control. Using the tool inside and outside, we found that we could place the beam height where we wanted: low for leveling a foundation or high for matching window heads -- and we could move the beam height in a hurry. The tool's reader worked well in bright light and its beam was easily visible inside.

I prefer tools with the simplest remote controls; most of the lasers we tested fall into this category. Again, Topcon's performed more functions than I wanted (that's a good problem to have), but I found it confusing to use. The LCI model is a little too simple: It only allows you to turn the level on or off, or rotate right or left.

Beam visibility, inside. All of these tools emit a visible beam in interior applications, but LCI's is the brightest and tightest. The better tools' (CST/Berger, Laser Reference, LCI, Stabila, and Trimble) have single-dot and chalkline modes making foundation, wall, and window head layout much easier -- especially with one person. The LCI and Laserjamb tools are our favorites for these tasks because their line beams are bright and easy to see. If the tool you like doesn't have a single-dot function, buy a remote reader if it doesn't come with one. The tools that only rotate (David White, CST/Berger) would be useless without remote readers because the beam generally spins too fast to see.

Beam visibility, outside. All the tools' laser lights disappear in bright light or over long distances, so you need a remote reader outside, too. These tools come standard with readers, and they all worked well. Some manufacturers include a pair of red enhancement glasses to help you view the beam in bright light, but I generally found them useless; the glasses were distracting and I couldn't see the beam any better. The Trimble and Topcon readers were the most reliable. They're comfortable to hold and the readers' output is easily understood.

Vibration dampening and auto re-set. My crew was most concerned about these two issues. Tool limitations quickly appeared when we set up in an old house with a bouncy floor. The better tools' internal mechanisms compensate for slight floor vibrations. When a tool shuts down because of movement, it's important that it quickly reset itself so that work can continue.

The Topcon level responded best on these two fronts. It shut down the least and reset itself the quickest. The Trimble, Laser Reference, and Laserjamb models also performed well. The Stabila level was disappointing; it's quite sensitive to vibration and shut down often and it didn't reset itself. We had to walk back to the tool and manually reset it. Stabila acknowledges that the model 05100 is a sensitive instrument and the company is redesigning it to correct the problem without compromising the tool's accuracy. A new model is scheduled to rollout this year, but it wasn't available for this test.

Alternative Tool

If you don't mind locating a single dot instead of a rotating laser, the TLZ. RoboLaser is your tool. For a fraction of the big boy's cost, this tool performs basic functions most contractors need for laying out and leveling horizontal surfaces. The RoboLaser is a self-leveling dot laser that spins 360 degrees. Its radio-controlled remote allows you to spin the dot in either direction. I found it quite reliable and easy to use. It's not the tool for squaring up walls or foundations or for setting vertical lines or slopes. But, if you only need it to level horizontal surfaces, you can't beat it for the price.

Favorites

After field-testing all the tools, we picked the Laserjamb level as our favorite of the bunch. The tool's versatile pole setup allowed me to set and adjust the bright, easily controllable beam anywhere from the floor to the ceiling. The level can also be used on a conventional tripod.

Close seconds are the Trimble and Topcon tools. They both performed well and each was the laser of choice among my carpenter crew. The other models performed closely in terms of accuracy and operation.

Picking the right tool is really a function of your personal use and accessory needs. The only one that I'd stay away from at this point is the Stabila 05100 model -- it's accurate, but it seems too sensitive to floor vibration.

"Shedding Light on Lasers"

By Clayton DeKorne

Small lasers packaged in compact boxes hold more promise than the point-and-shoot stick variety

Look before you buy. No construction laser will give you a line through space, and only a few will give you an actual line on the surface of wall or floor. The lines shown here come from the Laser Square SL-24 and Momentum Laser DP 90. Most lasers, however, project a single dot.

Pick up nearly any tool catalog or trade magazine and you’ll find a slew of construction lasers that claim to provide an efficient alternative to traditional layout methods. To be sure, laser technology holds great promise for the building trades, but this industry is still young. Many of the products available today may not prove as practical as you might first expect.

A Spectrum of Lasers

The commercial and industrial trades have been using lasers for years. Although the technology has changed in the last decade, the performance of these tools has been well established.

In the residential trades, however, the advantage of a laser is not so obvious. Nevertheless, scores of manufacturers have recently mobilized to deliver low-power visible lasers in small, relatively inexpensive packages.

For safety, the power output of any laser must be limited. Federal regulations set minimums for construction lasers at less than 1 milliwatt (Class II), and less than 5 milliwatts (Class IIIa). Even the brighter Class IIIa laser is safe for your eyes, as long as you don’t stare straight into the beam for a long time. But this low power rating also means that the beam isn’t very bright, and in strong sunlight, all of these lasers are very difficult to spot outdoors.

Dot Lasers

A dot laser is essentially a laser diode mounted on a level rail. Regardless of what some advertising photos show, these instruments project a dot, not a continuous beam; to be visible, the output of the laser must reflect off a target. Unless your site is shrouded in fog, you won’t see a continuous reference line shining through the air.

Accuracy for these instruments is defined by the speed of the vial and by two alignments one between the bubble and the rail, the other between the rail and the laser beam. Check the manufacturer’s specs carefully. Too often only one alignment, that between laser and rail, is given as the measure of accuracy. But the accuracy of an instrument is only as good as its weakest link, and on a dot laser, this link is usually the sensitivity of the vial. A 5-arc-minute vial works fine on a 4- or 8-foot stick. Project that line out 100 feet, however, and you could have an error of up to 3 inches. For accurate marks at longer distances, you need leveling accuracies measured in arc-seconds.

If you work with shorter distances, you must still keep in mind that a dot laser by itself can only project one dot in one direction. How often you have to set up to level a longer run will determine whether this type of laser is useful to your work. If you have to turn the corner and expect to keep your elevation, you’ll have to put up more cash for accessories namely, a swivel base or a beam splitter.

Most swivel bases rely on bubble vials, which add another layer of inaccuracy to the equation. And for every elevation you run, you have to level the base, then level the instrument. If you change elevations, then change back, you double the chances of getting an inaccurate reading. This leveling procedure reduces the dependability of these instruments to establish accurate repeat elevations. And the time you spend leveling the base and instrument seriously cuts into any labor savings.

A beam splitter typically uses some form of prism to divide the beam at 90 degrees, or at 180 degrees (90 degrees left and right). A few companies also offer a line lens, which spreads the beam into a line. The most versatile of these accessory systems comes from CheckPoint Laser. While you still have to deal with all kinds of extra parts, CheckPoint has packaged them in a job-site-friendly kit filled with a well-designed family of tools. The basic level a 1-foot-long, 1x2-inch rail milled to within .002 inch has been machined so that all sides of the rail can be used as references. All the relevant dimensions and centerlines have been carefully scribed on the tools. Perhaps the most ingenious feature is a protractor dial, complete with detents at common angles, for accurately projecting angles, either parallel or perpendicular to the instrument. Success with this tool will depend on how committed you are to learning new tricks. To get the full benefit of all its features, you almost have to become a student of the tool, much the way some folks have done with Construction Master feet-inch calculators.

Square Dots

LeveLite Technologies and Pacific Laser Systems incorporate beam splitting inside self-leveling instruments that provide several dots aligned at right angles. LeveLite makes two models the SLX2 and the Tri-Lite. The SLX2 shoots two dots at 90 degrees to each other. The top-of-the-line Tri-Lite adds a third dot for plumb. Pacific Laser’s PLS5 adds two more dots — one perpendicular to the plumb line in front, and another plumb line below the instrument.

Square dots. Though not much bigger than a tape measure, and nearly as durable, the Tri-Lite has won fans in the commercial interiors market for quickly plumbing steel partitions. The unit is self-leveling and accurate for distances under 50 feet.

Plumb, level, square. Accurate to 1/8 inch over 100 feet, the self-leveling PLS5 is one of the most exact instruments among the new breed of lasers. It has two plumb beams (one up and one down) and three level beams (at 90 degrees to each other), so you can accurately mark both ends of every layout line.

Because these instruments are self-leveling, setup is fast and dependable. The diode swings on the pendulum, allowing gravity to establish level. Provided the diode stays square to the pendulum, this bypasses the inaccuracies of a bubble vial.

The LeveLite tools (also sold in the Hilti and Quadriga lines) are accurate to within about 1/4 inch in 60 feet; the PLS5 is accurate to a much higher degree 1/8 inch in 100 feet. In this category, it seems, you get what you pay for. The SLX2 retails for about $500; the Tri-Lite goes for about $700; and Pacific Laser’s PLS5 sells for close to $1,000.

While this may sound like a lot of money to pay for a layout tool, it can make economic sense. According to Oakland remodeler Jonathan Dougall, the PLS5 has easily paid for itself several times over. I never hesitate to buy new tools to save labor, Dougall explains. In the work we do upper-level house remodeling we use the PLS5 all the time. The existing floor is never level, but everything above that windows, trim, cabinets, and ceilings must be dead on. Dougall used to use a transit for this work (and still does for most exterior layout). I’ve owned a couple of [stick] lasers, too, but I don’t use them anymore. For Dougall, the reliable self-leveling PLS5 offers a tangible time savings without sacrificing precision. A big part of this savings, claims Dougall, is in its being easy to use. Just set it down and wait a few seconds for the dot to settle out. There’s almost no training involved for the crew.

The plumb beams on the PLS5 and Tri-Lite are frequently employed for plumbing tall walls, and for setting the location of can lights in cathedral ceilings. Speeding up these applications alone can go a long way towards paying off the instrument. Dougall and other West Coast contractors note that 9-foot plate heights and vaulted interiors have become quasi-standard in upper-end residences, and lasers can speed this layout.

With its multiple reference points, the PLS5 offers the fastest alignment. In each reference plane, you get two dots that define one straight line. Dougall and other PLS5 users emphasize that these multiple reference points offer immediate and reliable checks. With other instruments, you are beholden to the level or plumb accuracy of the instrument, and you never have a concrete visual reference point for perfect alignment.

Square Lines

As a flooring contractor in northern Illinois, Dan Lewis long ago recognized that an easy-to-use laser device could substantially speed the installation of tile, carpet, and sheet goods. For this type of work, Lewis needed a tool that would show clear layout lines, not just a couple of abstract dots. His answer is the $650 Laser Square a simple instrument with two laser diodes aligned at a perfect right angle). Switchable optics make it possible to project three different patterns two dots, two horizontal lines, or two vertical lines. For floor layouts, the vertical lines prove the most useful. When projected low to the floor, these vertical lines show up on the deck as two solid lines of bright light. Whether you’re aligning wall plates, a tile grid, or a countertop, having a solid line to sight along speeds the task considerably.

Square lines. More of a layout tool than a long-distance leveling tool, the Laser Square gives you visible lines at a right angle. For some layout jobs, such as laying out floor tile or leveling a countertop, it’s more useful to have actual lines to sight along than a single reference dot.

Solidly encased in a heavy powder-coated aluminum body, the Laser Square seems built to last. This is one instrument you won’t hesitate to throw in a toolbox. Its ability to level is limited by two bubble vials. While this would work well for leveling a short run of kitchen cabinets, the real advantage of this instrument is in establishing square reference lines.

According to several tile installers, the Laser Square gives them an exact picture of the reference lines they need. This is a no-brainer, tile installer Todd Schwartz of Akron, Ohio, explains. The Laser Square is obvious to any floor mechanic who picks it up. Michael Byrne, director of the Ceramic Tile Education Foundation, echoes this claim. If an installer doesn’t understand the Laser Square, he or she needs training in the basic principles of layout. The Laser Square just makes these lines easier to see and quicker to establish. You can do the same thing with a chalk line and tape measure, though perhaps not as quickly.

Rotary Lasers

Rotary lasers are certainly nothing new in the building trades. Now built with laser diodes, these instruments have gotten much more affordable, but they are still more appropriate for production interior work. Commercial drywall and ceiling contractors represent the biggest market for the latest rotary lasers.

Most rotary lasers have a fixed diode that projects its beam straight up, while an angled mirror directs the beam horizontally. When this mirror spins, the moving dot appears as a line in a circle around the instrument. The light energy becomes dispersed along the line, so it’s much dimmer than when all of that energy is concentrated in one dot. For this reason, low-end rotary lasers aren’t bright enough for exterior work without an electronic detector. Some rotary models split the beam so half of it shines straight up. While this further decreases the visual brilliance of the beams, it provides a useful plumb reference for interior work. A few rotary models also feature a sweep mode (also called dithering). Here, the laser oscillates back and forth, projecting the beam in a small arc (about 10 degrees) that shows up as a much brighter but shorter line. Even with sweep mode, however, the only practical way to see a rotary laser in bright sunlight is with an electronic receiver.

Rotary level. A visible laser beam becomes nearly invisible in bright sunlight. So rotary lasers made for exterior layout typically include an electronic detector a small box that clamps to the measuring rod. The detector converts a signal from a sensor (similar to a photo cell) into an LED light display. The sensors have been tuned to absorb light of a specific wavelength, so they can see the laser beam in all exterior conditions.

As with any fixed laser, unless the instrument is self-leveling, you have to level it by hand using bubble vials. Fortunately, many rotary lasers depend on vials of higher quality than you’ll find on most dot lasers.

Unless you specialize in commercial interiors, the cost of a conventional rotary laser is hard to justify. At least one company, however Momentum Lasers of Santa Clara, Calif. has built a line of affordable and functional rotary lasers that, for the starting price of about $300, begin to make sense for low-volume custom projects.

These machines use a diode mounted directly on a rotating head, which simplifies the optics and makes for a much less fragile machine. The company’s original LaserChalkline features two diodes in the rotating head, which doubles the light, creating a much brighter beam. This model has been targeted for the drop-ceiling trade. Two other models have only one diode each. Momentum markets these in kits: The XL, designed for exterior work, comes with a simple electronic detector; the SL is aimed at finish carpenters. To make it more useful when establishing multiple elevations, Momentum offers an optional Laser Slide a spring-loaded pole that can be set up quickly between ceiling and floor. A moveable bracket holds the laser, and allows for easy repositioning. All of these Momentum lasers have variable-speed rotation.

The newest Momentum laser the $600 DP 90 competes directly with the Laser Square. This model has two rotating heads that paint two laser lines at 90 degrees to each other. In this case, the lines extend not only across the floor, but also up each wall and across the ceiling, defining two planes at right angles to each other. The DP 90 has only been introduced recently, but we did locate one commercial installer, Mark Newman of Orange County, Calif., who reports that the DP 90 has worked well for squaring and plumbing metal studs. Because the diodes rotate, the lines are dim in large interiors. Momentum offers laser-enhancement glasses with red lenses that make the laser lines stand out. While the glasses work, Newman says they cut down general visibility.

Rotary square. The Momentum DP 90 features two rotating diodes positioned at right angles. These project visible right-angle lines on the floor, as shown, as well as on the ceiling and walls.

Moveable Dot

The RoboToolz RoboLaser (RT-7210-1) could easily be mistaken for a rotary laser. But unlike conventional rotary machines, this one doesn’t generate a circumference line. Instead, the single dot can be slowly rotated, using a hand-held remote control. Because the beam doesn’t rotate, it tends to be much brighter outdoors, though still difficult to find in direct sun.

Moveable dot. The single laser dot emitted by a self-leveling RoboLaser (RT-7210-1) can be moved to any position with a hand-held remote. While the machine turns slowly, the dot tends to be much easier to locate than the dim line made by the spinning dot from a rotary machine.

Of all the low-end lasers out there, the $300 RoboLaser (RT-7210-1) lends itself best to traditional layout methods for exterior work. It’s self-leveling, so setup is fast. And it’s accurate to within 1/4 inch over 100 feet, so it can be used reliably over long distances. The unit can be mounted on a tripod at a safe distance from the scurry of workers and machines on site, and the laser dot can be moved using the remote control to establish multiple reference points.

Beyond Marketing

Choosing the right laser layout tool begins with seeing through the marketing hype. Manufacturers want to appeal to the pros, and with good reason. The use of light beams to establish accurate line and angle projections has obvious advantages in the trades, and even many of the current designs can be extremely useful at speeding up some layout jobs. Yet many advertising campaigns aimed at the trades want us to believe that a particular laser will replace our levels, string lines, plumb bobs, even tape measures. Lasers do have a place in the trade, and their use will grow as manufacturers refine the technology and as tradespeople become familiar with their features. But string lines and tapes measures aren’t going out of style anytime soon.

Choosing a laser may also mean having to rethink not only our expectations, but how we do the work. Many laser tools have proven cost-effective for some contractors. Most of the satisfied buyers we’ve found in the trades have enough repeat production layout to see a quick return in labor savings. Not surprisingly, many of these buyers work on larger-scale commercial interiors. But even among custom-residential users, the decision to buy was based on an expected improvement in production, and was weighed against both the price tag of the tool and how much retraining would be required. In most cases, satisfaction also required some creative insight on the part of the contractor and the crew to find the best way to approach the job with a laser.

"Stalking the Affordable Laser"

By Clayton DeKorne

As technology evolves, specialized lasers have found strong trade markets. But the hunt for an affordable, all-purpose construction laser continues.

Q. There are so many new lower-cost construction lasers out there, we're not at all sure what to buy. We're a medium-sized custom homebuilder, and we're looking for one good instrument that we can use throughout a project. Can you steer us in the right direction?

A. Clayton DeKorne responds: Yes, there are a lot of lasers out there. Low-cost construction lasers are one of the most rapidly developing new tools on the market. In the last five years alone, scores of relatively inexpensive stick lasers ($100 to $500), box lasers ($450 to $900), and scaled-down rotary lasers ($250 to $1,500) have been pitched primarily at residential and light-commercial contractors. All of these are sold as easy-to-use and accurate layout tools. But, then, so are the high-end lasers that have been sold in the heavy construction market for decades. Buyers of the new affordable tools deserve to know the difference.

What a General Needs

Without going through an exhaustive catalog of distinguishing features, let's look first at the essential features that "one good instrument" must have. Regardless of what a laser costs, we feel strongly there are a few key features that laser manufacturers cannot compromise, if that laser is to rightly serve the "general" construction market.

Accuracy: To be useful in a wide range of applications, a general construction laser should be accurate to within at least 1/4 inch at 100 feet. However, even the best 3-arc-minute bubble vial (used on the Sonin Range Level) is only accurate to within about 1/2 inches at 100 feet. Most lasers that rely on a bubble vial use less-sensitive 5- to 7-are-minute vials, which are accurate to anywhere from 3 to 5 inches at 100 feet. This does not account for any compound inaccuracies from parallelism (how true the laser beam runs to the level rail), parallax (from not looking straight at the bubble), and the physical limitations of any mechanically leveled instrument that's subjected to site conditions (such as fluctuating temperatures and vibration).

But even if we accept the manufacturer's tested accuracy, the most important issue at stake here is what's an acceptable working range. Many manufacturers argue that an accuracy range of as little as 1/4 inch at 30 feet is acceptable for residential applications, which don't often require long layouts.

We don't think this necessarily holds true. A working distance of 100 feet is essential even on some small residential sites, if only to give the user a greater opportunity to establish one fixed reference point that can be left undisturbed, can easily be reestablished, and is easy to get to "throughout the project." By definition, a general construction laser must be versatile, and the further a user can transfer an accurate reference line, the more versatile that instrument becomes.

Repeatability: Layout is seldom a matter of projecting just one reference line. Almost always, that first line must be accurately transferred to any number of locations around the site. Consistency is key. A contractor needs to be able to easily and quickly come back to the same reference line over and over again through the course of a job. That's what gives a laser its advantage over strings, batter boards, story poles, and other ungainly work-arounds.

High-end rotary lasers have always done this best, allowing a user to set up the instrument in a safe spot, and reference any measurement from its beam. Lower-cost "point-and-shoot" lasers, of course, don't let you easily pick off a point, without manually rotating the instrument on a three-point leveling base (usually an accessory). And unless this base is precisely leveled in all directions, the chances of accurately repeating measurements are slim.

When you raise the issue of repeatability, a single tested accuracy becomes even more irrelevant. All the inaccuracies caused by site conditions, climate, and user error become impossible to ignore. Working on true job sites in real time calls for an instrument that can be repeatedly leveled from a constant center. Currently, the only practical way to achieve this reliability is with a self-leveling instrument. Here, at least gravity provides a constant reference independent from mechanical and physical limitations.

Visibility in sunlight: Unless a contractor does all his work indoors, a laser level must be visible in sunlight. Few lower cost ($100 to $650) diode lasers are very effective outdoors. The time you spend finding the dot defeats the need for establishing a quick reference point.

Traditionally, high-end lasers have used gas-tube lasers, rather than diodes. These require lots of power (read: big batteries) but throw off lots of energy, so they can be seen in all light conditions. The best of these still use delicate helium neon (HeNe) tube lasers, though with advanced (read: expensive) optics, some new lasers with high-powered diodes have made inroads into the high-end laser market.

Low-cost rotary lasers are particularly difficult to spot outdoors. Rotary lasers scatter the laser energy along the sweep of its path - in essence, diluting the brightness. Before you buy any laser, make sure you're satisfied with the beam brightness outside.

Many manufacturers try to address beam brightness by offering infrared lasers for exterior use. You can't see the infrared beam at all; you need a sensor to detect the beam. However, I'm not convinced this is a practical solution. Using the sensor defeats the purpose of a single reference station that can be immediately accessed throughout the job.

What's Out There

The construction laser industry is very much in a state of becoming. Many of the affordable new models have found excellent uses among the trades, but mostly for specialized work. For example, L. P. Industries claims its Laser Square is designed to be accurate to within 1/4 inch at 60 feet. However, it provides exactly the kind of reference lines that tiling contractors need to establish and its accuracy range fits a wide range of tile applications. Also, the LeveLite and PLS5 -- two self-leveling instruments -- have won fans among steel framers, commercial outfitters, and other specialty contractors, mostly used indoors at distances below 60 to 75 feet.

So far, the only "low-cost" laser on the market that I think comes the closest to providing all the essential features required for general construction is the RoboLaser from Toolz. It's self- leveling (once you get it within 10 degrees) and accurate to within 1/4-inch at 100 feet, which makes it practical to set the instrument up at a safe distance during the job, and still get accurate reference lines.

What makes the RoboLaser unique is a remote control that allows you to point the single laser beam to any spot in a circle around it. This (almost) gives you the convenience of a rotary laser without scattering the energy. As a result it is (almost) always detectable outdoors. My hesitations with this laser are that it's still difficult to see outdoors, but far better than most low-cost rotary lasers (the on/off indicator on the unit gives you a hint as to where the beam is pointing). It's also slow, compared to a rotary laser, but much faster and more convenient than any point-and-shoot model). Unlike a rotary laser that sweeps its line quickly, you have to wait for the remote to turn the unit. It also takes some time to get used to fine-tuning the remote to hit an exact mark. However, you can use the remote to turn the laser on and off, or to bring the beam wherever you need. At a cost of about $300, it could prove to be the best general construction laser in the affordable price range.