What Causes Fret Buzz and How to Diagnose It

Fret buzz is the metallic rattling sound you hear when a string vibrates against a fret it should not be touching. On an acoustic guitar, this happens because the neck has lost its curve, one or more frets are higher than their neighbours, or the strings are set too low. The buzz usually gets worse on certain frets or in certain positions on the neck.

To diagnose where the buzz is coming from, hold the guitar in playing position and pluck each string individually while fretting it at different positions up the neck. Listen carefully to which frets produce the rattle. If the buzz happens only on the lowest frets, the neck may have lost its forward curve. If it happens in the middle of the neck or on just one or two frets, a single high fret is usually the culprit. If all strings buzz equally across the whole neck, the bridge or nut may be too low.

A straightforward test: place a straightedge (a ruler or level) along the frets from the headstock to the body. Look for gaps between the straightedge and the frets. A small gap at the middle of the neck is normal and necessary—this is called relief. If the frets are perfectly flat or if the straightedge rocks on high spots, you have found the problem.

Key Takeaways

  • Fret buzz comes from a string hitting a fret it should not touch, caused by a straight or back-bowed neck, a high fret, or strings set too low.
  • You can test for neck relief using a straightedge and a feeler gauge, and adjust the truss rod if the neck has lost its curve.
  • If a single fret is high, it can be levelled by a technician, but attempting this yourself risks damaging the fretboard.
  • Raising the bridge or nut slightly can reduce buzz caused by low string action, though this changes how the guitar plays.
  • Many cases of fret buzz are temporary and caused by humidity changes, so monitor the problem over a few weeks before making permanent adjustments.

Checking and Adjusting Neck Relief with the Truss Rod

The truss rod is a metal rod inside the neck that controls how much forward curve (relief) the neck has. Most acoustic guitars have a truss rod access point at the headstock, usually hidden under a cover or visible as a slot. Before you touch it, take a photo of the current position so you can return to it if needed.

To measure relief accurately, place a straightedge along the frets and use a feeler gauge (a set of thin metal blades, available at hardware stores for under $10) to measure the gap at the seventh fret. The gap should be between 0.010 and 0.015 inches—roughly the thickness of a business card. If there is no gap or if the straightedge rocks on high frets, the neck needs adjustment.

Turn the truss rod adjustment nut very slowly—one-quarter turn at a time—and wait 10 to 15 minutes between adjustments to let the wood settle. Turning clockwise (when viewed from the headstock) reduces relief and flattens the neck; turning counterclockwise adds relief and increases the curve. Make one small turn, then recheck with the straightedge. This process takes patience. If you turn the rod more than one full rotation without seeing change, stop and consult a technician—forcing it can crack the neck.

When a Single Fret Is Too High

If your straightedge test shows that only one or two frets are higher than their neighbours, the problem is a high fret, not a neck curve issue. This is harder to fix at home because it requires removing the fret, levelling the fretboard, and reinstalling it—or replacing the fret entirely.

A temporary solution is to shim the bridge or nut slightly to raise all the strings above the high fret. This reduces buzz but makes the guitar harder to play because the strings sit higher. This is a band-aid fix and works only if the high fret is very close to the bridge or nut.

For a permanent solution, take the guitar to a technician who can level the frets or replace the high one. This typically costs $100 to $300 depending on the shop and how many frets need work. Attempting to file or sand frets yourself risks damaging the fretboard and making the problem worse.

Raising the Bridge or Nut to Reduce Buzz

If the entire neck has good relief but the strings are still buzzing because they sit too close to the frets, raising the bridge or nut will help. The bridge is easier to adjust: you can sand the bottom of the bridge to lower it (reducing action) or glue a shim underneath to raise it (increasing action). The nut is harder because it is glued in place and removing it risks splitting the headstock.

To raise the bridge, remove the bridge pins and lift the bridge straight up. Sand the bottom surface very lightly with 120-grit sandpaper to remove any glue residue, then measure how much higher you need it. A shim made from hardwood veneer (available at craft stores) glued under the bridge will raise the action by a predictable amount. Glue the shim with hide glue or epoxy, clamp it overnight, then reinstall the bridge and pins.

Raising the action makes the guitar harder to play because your fingers have to press the strings down farther. It also changes the tone slightly, usually making it louder and brighter. Make small adjustments—raising the bridge by 1/16 inch is noticeable. If you raise it too much, you can always sand it back down or remove the shim.

How Humidity Changes Cause Temporary Buzz

Acoustic guitar necks are made of wood, and wood moves with humidity. In winter when the air is dry, the neck can shrink and lose relief, causing buzz. In summer when humidity is high, the neck swells and gains relief, and the buzz may disappear. This is why fret buzz that appears in one season sometimes vanishes in another.

If you notice buzz appearing or disappearing with the seasons, do not make permanent adjustments to the truss rod or bridge yet. Instead, monitor the guitar over several weeks. Keep the guitar in a room with stable humidity—ideally between 40 and 50 percent relative humidity. A humidifier in winter or a dehumidifier in summer can help stabilize the neck.

If the buzz is seasonal and mild, you may decide to live with it rather than adjust the guitar. If it is severe or year-round, then the neck has a structural problem that needs fixing.

Tools and Materials You Will Need

For diagnosing and adjusting fret buzz, gather these items before you start: a straightedge or level at least 24 inches long, a feeler gauge set, a truss rod wrench (usually included with the guitar or available from the manufacturer), 120-grit sandpaper, hide glue or epoxy, hardwood veneer shims, and bridge pins if you remove the bridge.

You do not need expensive tools. A metal ruler works as a straightedge, and a feeler gauge costs less than $10. A truss rod wrench is specific to your guitar model—check the manual or contact the manufacturer to find the right size. If you do not have the wrench, a technician can make the adjustment for $30 to $50, which may be worth it if you are uncertain about the process.

When to Take Your Guitar to a Technician

Some fret buzz problems are beyond a home fix. If the straightedge test shows multiple high frets scattered across the neck, the fretboard may be warped and need professional levelling. If the truss rod does not respond to adjustment or feels stuck, forcing it can crack the neck. If you are unsure whether the problem is the neck, bridge, or nut, a technician can diagnose it in minutes.

A setup by a professional technician—which includes checking neck relief, adjusting the truss rod, shimming the bridge if needed, and filing the nut and bridge—typically costs $75 to $150. This is money well spent if you are not confident in your own adjustments, because a mistake can damage the guitar permanently.

Frequently Asked Questions

Can I use a capo to test for fret buzz?

Yes. Place a capo at the first fret and look at the gap between the strings and the frets behind the capo. If the strings sit very close to or touch the frets, buzz is likely. This is a quick visual check, but using a straightedge and feeler gauge is more accurate.

Will new strings fix fret buzz?

New strings will not fix buzz caused by a straight neck or high frets, but they may reduce buzz slightly because new strings have more tension. If buzz disappears completely with new strings, the old strings were worn or damaged. If it remains, the problem is the neck or frets.

How much does it cost to have a technician fix fret buzz?

A truss rod adjustment costs $30 to $50. Levelling one or two high frets costs $100 to $200. A full fret levelling and crowning (when many frets are uneven) costs $200 to $400. Prices vary by location and shop.

Is fret buzz permanent damage to the guitar?

No. Fret buzz is a symptom of a problem with the neck, bridge, or nut—not damage to the wood itself. Once the underlying problem is fixed, the buzz goes away and the guitar plays normally again.

Can I prevent fret buzz by storing my guitar in a case?

A case protects the guitar from physical damage and helps stabilize humidity, which reduces the risk of buzz caused by seasonal wood movement. However, a case alone will not prevent buzz if the neck has a structural problem or if a fret is high.