A floor that feels slightly springy after installation, or a hardwood surface where seams develop noticeable height differences, usually points to one root cause: the subfloor wasn't properly checked before installation.

A 6-foot straightedge only evaluates one narrow strip at a time, which means a low spot just a couple of feet away can easily go unnoticed. A laser level maps the entire room against a single reference plane, allowing every measurement to share the same baseline.

This guide covers two practical applications: checking and preparing a subfloor for wood flooring, and using the same tool to establish center reference lines and guide tile layout.

What "Flat Enough" Really Means: NWFA and TCNA TolerancesNWFATCNA

"Flat enough" isn't subjective—it's defined by measurable standards. The NWFA (National Wood Flooring Association) and TCNA (Tile Council of North America) publish specific subfloor flatness tolerances. These are the same benchmarks flooring manufacturers use when evaluating warranty claims.

Flatness Requirements for Wood Flooring (NWFA Ch. 4)NWFA

NWFA Installation Guidelines Chapter 4 ties allowable subfloor tolerance directly to the installation method:

Floating engineered floors follow the same standard. NWFA notes that "subfloor flatness is critical to the success of a floating floor installation." [1]

Tile Flatness and Lippage Standards: Large-Format Tiles Are Stricter (TCNA/ANSI)TCNAANSI

TCNA guidelines specify additional requirements for tile installations:

• Standard tile (any side under 15"): ¼" per 10 ft
• Large-format tile (any side 15" or larger): 1/8" per 10 ft, which is twice as strict as the nail-down hardwood standard
• Lippage (height difference between adjacent tile edges): no more than 1/32" per ANSI A108.02 [2]

Most installation guides recommend checking flatness with a 6-foot straightedge. That method only measures one strip at a time, and every repositioning resets the reference point.

A laser level projects a continuous horizontal plane, allowing you to measure multiple locations across the room against the same reference.

Does the CM-701 Meet These Standards?

The CM-701 has an accuracy rating of ±0.3mm/m, which translates to roughly ±1/8" per 10 ft. This meets every tolerance listed above, including the stricter requirement for large-format tile. If you're comparing tools for your project, see our laser level buying guide.

What You Need Before You Start

You'll need:

• CM-701 laser level (a tripod is strongly recommended)
• Tape measure, at least 10 feet
• Chalk or an erasable marker
• For wood floors: belt sander or angle grinder with dust collection for high spots; self-leveling compound and a trowel for low spots
• For tile: chalk line for transferring the laser reference; tile spacers

Mount the CM-701 on a tripod at the center of the room and power it on. Wait until the indicator light stops flashing and remains steady before taking measurements.

A steady light indicates that the auto-leveling process is complete.

Pro Tip: Let the CM-701 warm up for 2–3 minutes before measuring. The laser diode shifts slightly as it reaches operating temperature, so readings taken immediately after power-on can be off by a few millimeters. If you start marking right away, every measurement may be based on a false baseline.

How to Check and Prep a Subfloor for Wood Flooring: Step-by-Step

Work in two phases: first scan the entire room to identify problem areas, then correct them.

Avoid filling low spots before grinding down high spots. Grinding dust that settles on freshly cured self-leveling compound can weaken its surface bond.

1. Place the tripod at the center of the room and power on the CM-701. Before starting any major project, calibrate your laser level, especially if it has been dropped or bumped since the last use.
2. Enable the 360° horizontal line mode. Walk the room perimeter and measure the distance from the laser line to the floor every 1–2 feet using a tape measure. Record each measurement.
3. Identify the reference point, which is the highest reading in the room. All other measurements are compared against it. For glue-down or floating floors, deviations greater than 3/16" per 10 ft require correction. For nail-down hardwood, the limit is ¼" per 10 ft. These tolerances come from NWFA Chapter 4 [1].
4. Mark high and low spots immediately. Use chalk circles for high spots (to grind) and X marks for low spots (to fill). Once the tripod moves, the original reference is lost.
5. Grind down the high spots. Grinding concrete or hardwood produces crystalline silica dust. According to OSHA 29 CFR 1926.1153 [3], use a NIOSH-approved respirator, a vacuum-equipped grinder, or wet grinding methods.
6. After grinding all high spots, fill low spots with self-leveling compound. For dips deeper than ½ inch, apply the compound in layers no thicker than ¼ inch, allowing each layer to cure before adding the next.
7. Re-scan after the compound cures. Self-leveling compound shrinks slightly during drying. Check the entire room again before installing flooring. The same scanning approach is used in larger projects such as leveling ground for slabs or patios.

Pro Tip: Mark high and low spots immediately after scanning. If the tripod moves, your reference points disappear. Also remember to grind high spots before filling low spots—grinding dust settling on cured leveling compound can weaken its bond.

How to Use a Laser Level for Tile: Finding Center and Guiding Alignment

A laser level serves two purposes in tile work: verifying that the subfloor meets TCNA flatness standards and establishing perpendicular reference lines to control the layout.

Many tile guides suggest starting from a corner, but corners are rarely perfectly square. Beginning there often pushes alignment errors toward the center of the room, where they're most visible.

Starting from the center keeps the tile field symmetrical while cut tiles fall along the walls, where they are less noticeable.

1. Find and mark the midpoint of each wall. Connect opposite midpoints to locate the layout center.
2. Switch the CM-701 to cross-line mode and position it at the center point. The perpendicular laser lines form your layout grid. This replaces the traditional trammel-point squaring method described in NWFA Appendix G, without cumulative measurement error.
3. Dry-lay tiles from the center outward along one axis to evaluate corner cuts. Ideally, cut tiles along the walls should be at least half a tile wide. If not, shift the center point slightly until the layout balances.
4. Snap chalk lines along the laser references. Once adhesive is spread, the laser line will be difficult to see. Chalk lines become your working guides.
5. Set the first tile at the chalk-line intersection and work outward. Re-check alignment against the laser every 3–4 rows.
6. Check lippage as you install. Run a finger across adjacent tile edges before the adhesive sets. According to TCNA ANSI A108.02 [2], lippage should not exceed 1/32". For large-format tiles (any side 15" or larger), the subfloor must meet the stricter 1/8" per 10 ft requirement. If an edge is noticeable, adjust mortar thickness while it's still workable. See the full CIGMAN laser level buying guide for model recommendations by project scale.

Pro Tip: Re-check alignment against the laser every 3–4 rows. A drift of just 1/16 inch per row can become nearly half an inch by the far wall. Catching the issue early takes seconds; fixing it later may require relaying a large section.

Common Mistakes and What They Actually Cost You

Skipping the Warm-Up

The laser diode shifts slightly as it reaches operating temperature. Readings taken in the first minute after power-on create a false baseline.

Fix: Let the CM-701 warm up for 2–3 minutes before taking any measurements.

Bumping the Tripod

If the tripod moves, every measurement loses its reference and chalk markings may no longer be accurate.

Fix: Mark tripod leg positions with tape before scanning. If it gets bumped, reposition precisely using the tape marks before continuing.

Not Re-Checking After Self-Leveling Compound Cures

Self-leveling compound shrinks slightly as it dries, which can leave shallow dips even where you filled.

Fix: Always re-scan after the compound cures. The same principle applies to larger projects, whether indoors or when leveling ground outdoors.

Skipping the Moisture Content Check

A laser level measures flatness, not moisture. Even a perfectly flat subfloor can cause problems if moisture content is out of range.

Fix: Always verify moisture content with a calibrated moisture meter before installation.

Frequently Asked Questions