Fretboard Shrinkage: Dry Frets and Sharp Edges

What is fretboard shrinkage?

Wood is a natural material that releases and absorbs moisture from the air. When the surrounding air is very dry, a fretboard can lose moisture and contract. Because the metal frets are not affected by humidity, they end up sticking out beyond the edges of the wood. This is often called fretboard shrinkage, and it's a common issue on guitars with rosewood or ebony fretboards.

Guitar builders select woods like rosewood and ebony for fretboards because of their density and feel, as noted in Martin's wood guide. These woods are dense and hard, making them durable for fretting, but they still respond to changes in humidity. The degree of movement depends on the wood species, the cut of the wood, and the finish. Unfinished fretboards are especially vulnerable because they have no barrier to slow moisture exchange.

In most cases, the shrinkage is temporary. When the humidity returns to a normal range, the wood expands back to its original size, and the fret ends retreat under the edges. However, if the guitar is exposed to very dry conditions for a long time, the wood can develop cracks or the frets can become loose. That is why understanding this phenomenon is important for any guitarist who wants to keep their instrument in good shape. For a deeper look at fretboard woods, see this guide to guitar neck wood types.

Why rosewood and ebony?

Rosewood has greater density and hardness than most other tonewoods, which makes it a popular choice for fretboards and bridges. It is prized for its warm, resonant tone and its smooth feel under the fingers. Ebony is also a dense hardwood often used on high-end instruments, offering a bright attack and a very smooth surface. These woods are classic choices for both acoustic and electric guitars.

The same properties that give these woods their tonal character also make them responsive to the environment. When the wood dries, it shrinks across the grain, which is the direction of the fretboard width. This is why the fret ends poke out on the sides rather than along the length. Because the frets are installed in slots that run across the board, any width contraction makes the fret wire longer than the wood.

Additionally, many rosewood species are regulated under CITES, which means that international trade requires permits. This has led some builders to use alternative woods like pau ferro or granadillo, but rosewood and ebony remain the standard for many players. You can read more about the differences in this comparison of rosewood and ebony fretboards.

Signs and symptoms

If you notice any of the following signs, it's likely that your fretboard has lost some moisture. The most common symptom is a sharp edge along the side of the neck where the fret ends protrude. This can make the guitar uncomfortable to play, especially when you slide your hand up and down the neck. You might also feel the fret ends catch on your palm or your fingers.

Another sign is a change in the way the strings feel. If the fret ends are higher than the wood, they can cause the strings to catch when you bend or release a note. In more severe cases, you might hear a subtle rattle or buzz when you play open strings or fretted notes near the edges. This happens because the string can momentarily hit the protruding fret wire.

You can check for fretboard shrinkage by running your hand along both edges of the neck. If you feel any roughness or sharpness, it's time to take action. You can also use a straightedge across the fretboard to see if the wood is level with the frets. For a detailed guide on fret-related issues, see this article on fret wear and leveling.

• Fret ends that protrude beyond the wood edge
• Sharp and uncomfortable edges under the fingers
• Strings catching on the fret ends when sliding
• Buzzing or rattling sounds when playing
• A general rough feel along the neck

How humidity affects wood

Wood is hygroscopic, meaning it gains and loses moisture from the air. In a high-humidity environment, wood absorbs moisture and swells. In a low-humidity environment, it releases moisture and shrinks. This is a natural and reversible process, but it can cause problems if the changes are extreme or rapid.

The ideal relative humidity for guitars is generally considered to be between 45 and 55 percent. When the humidity drops below 40 percent, the wood begins to lose moisture more quickly. Home heating systems in winter can easily lower indoor humidity to 20 percent or less, which is why fretboard shrinkage is most common during the heating season.

The construction of the guitar also matters. A solid wood acoustic guitar with a thin top is more sensitive to humidity changes than a guitar with a laminated top. The fretboard, however, is almost always a solid piece of wood, regardless of the body construction. So even an entry-level guitar can experience fretboard shrinkage if it's exposed to very dry air.

The rate of moisture exchange depends on the surface area and the finish. An unfinished fretboard, like those on most acoustics, responds faster than a finished maple neck, which has a sealed surface. This is why maple fretboards are often used on electric guitars: they are less prone to visible shrinkage because the finish prevents rapid moisture loss.

Prevention: humidification

The best way to avoid fretboard shrinkage is to keep your guitar in a stable environment. Using a case with a humidifier can help maintain a consistent moisture level. For practical steps, see this guide on using a guitar humidifier. Also, storing your guitar properly when not in use reduces the risk of drying.

There are several types of guitar humidifiers available. Some attach to the strings and sit inside the soundhole on an acoustic guitar. Others are designed to be placed in a case or a room. Always monitor the humidity with a hygrometer to make sure you're not over-humidifying, which can cause its own set of problems like a bulging top or lifting bridge.

If you live in a dry climate or your home is heated during the winter, consider using a room humidifier in the room where you keep your guitar. This can help maintain a stable environment for all your instruments. If you travel with your guitar, use a hardshell case with a good seal and keep the humidifier in the case.

For more detailed advice on storing guitars, check this article on safe storage.

Repair: fret dressing and crowning

If the fret ends are already protruding, a guitar technician can file them down and recrown the frets. This process removes the sharp edges and restores a smooth feel. For a detailed step-by-step, see this guide on fret end filing and this guide on fret crowning and recrowning.

The first step is to protect the fretboard from scratches. A luthier will tape off the wood and then use a fine file to gently remove the excess fret wire. The goal is to file the fret ends until they are flush with or slightly beveled below the wood edge. After filing, the fret ends are dressed with a small bevel to avoid any sharpness.

If the fret ends have caused the frets to become loose, a drop of cyanoacrylate glue can be used to secure them. The luthier will then recrown the fret tops to restore the correct curvature and polish them to a smooth finish. This is a skilled job that requires the right tools and experience.

In some cases, the fretboard may have shrunk enough to cause the frets to develop a slight curve or 'smile' across the top. This can cause buzzing on certain notes. A full level and crown job may be necessary to correct the issue. You can learn more about the process in our guide to fret crowning.

When to see a luthier

In severe cases, the fretboard may shrink enough to cause frets to become loose or the wood to crack. If you notice frets that move or a visible gap between the fret and the wood, take the guitar to a professional luthier. They can evaluate whether a partial refret or a fretboard replacement is needed. Our guide on fret wear and leveling covers related maintenance.

A cracked fretboard is a more serious issue. If you see a crack along the wood, usually near the frets or at the edges, do not try to repair it yourself. A luthier will need to stabilize the crack, possibly using wood glue and clamping, and then address any fret issues. In rare cases, the fretboard may need to be replaced entirely.

If you're buying a used guitar, check the fret ends carefully. Protruding fret ends may indicate that the guitar was not properly humidified at some point. While it's often an easy fix, it could also be a sign of other humidity-related problems, such as a warped neck or a cracked top. Buying from a reputable source reduces this risk.

For more information on what to look for in a new guitar, see our best acoustic guitars and best electric guitars guides.

Choosing a guitar to avoid this

If you live in a particularly dry climate and want to minimize maintenance, you might consider a guitar with a maple fretboard. Maple is less prone to visible shrinkage than rosewood or ebony, though it offers a different feel and tone. You can read more in our comparison of maple and rosewood fretboards.

Some builders use alternative woods like pau ferro, which is similar to rosewood in density and tone but less regulated and often more stable. Others use richlite or other synthetic materials, which are completely unaffected by humidity. These can be great options if you want a fretboard that requires no climate management.

However, many players prefer the feel and sound of traditional rosewood or ebony. The choice is a personal one. If you go with rosewood or ebony, be prepared to take preventive measures. The good news is that fretboard shrinkage is usually a minor inconvenience that can be fixed with a simple dress and a proper humidification routine.

When shopping for a new guitar, consider the wood choices and the climate you live in. Our buying guides can help you compare models with different fretboard woods. Check out the best guitars for beginners or travel-friendly models for a range of options.

What to pick for your use

Questions

How do I know if my fretboard is shrinking?

Look for fret ends that protrude beyond the wood edge, sharp edges, or strings catching when you slide. These are common signs that the fretboard has lost moisture.

Can I fix fret popping myself?

You can try filing the fret ends carefully, but it's easy to damage the fretboard. For a clean result, have a guitar technician do it, especially if you're not experienced with fret work.

What humidity level should I maintain?

Keep your guitar in an environment that feels comfortable for you. Avoid placing it near heaters, air conditioners, or direct sunlight. Using a room humidifier or a case humidifier will help maintain stable conditions.

Does maple fretboard shrink too?

All wood reacts to humidity, but maple is generally less affected than rosewood or ebony. If you want to minimize the chance of fret ends poking out, a maple fretboard is a good choice.

How often should I humidify my guitar?

In dry seasons, check the humidity regularly. If the air feels dry, use a humidifier in the case or room. The goal is to keep the wood from drying out, not to achieve a specific level.

What causes fretboard shrinkage?

Low humidity causes wood to release moisture and shrink. When the fretboard shrinks, the metal frets stick out. This is common in winter when indoor heating dries the air.

Can fretboard shrinkage cause cracks?

Yes, severe dryness can cause the wood to crack, especially along the grain or near the fret slots. If you see a crack, take the guitar to a luthier immediately.