Acoustic Guitar Crack Repair: What Is Involved

Body cracks happen to a ton of acoustic guitars. Humidity plays a role, temperature plays a role, and the way the guitar gets treated plays a role. The one on the bench today is a very high end classical guitar from Madrid with a significant crack from being dropped, and you can see the damage on the heel too. That one is going to take days of work. Most cracks are nowhere near as involved, and the message of this page is the same for both: properly repaired, a cracked guitar can be incredibly stable for the rest of its life.

Where cracks usually start

The classic acoustic crack is 6 to 8 inches long, running behind the bridge toward the tail of the guitar. There is a reason it starts there. As the top shrinks in dry air, the bridge pins do not shrink with it, so each pin becomes a little pressure point, and the crack lets go from the back of the bridge. We see it constantly, and a dry Calgary winter is usually all it takes. No drop required.

How we repair them

There are a couple of ways to approach it. The standard repair is to swell the crack closed, glue it with a proper wood glue, and then make and install a cleat on the inside, a small piece of wood spanning the crack that reinforces it from behind. That is a stable, proven repair.

On higher end instruments we will often use a CA glue to stabilise the crack instead. It is much stronger, and it can be sanded and buffed until it essentially becomes part of the finish, which matters on a guitar where appearance is part of the value. You can see examples of both on our before and after page.

The Calgary factor

Our winters are hard on acoustics. The air goes bone dry, tops shrink, and guitars that live on stands next to heat vents suffer most. A case humidifier from November to March is the cheapest insurance there is, and it is exactly the kind of thing we will flag during a setup assessment before it becomes a repair.

Common questions

Is a crack in my acoustic guitar serious?

It is worth taking seriously, but it is rarely fatal. Cracks tend to grow and collect grime if ignored, and a clean, recent crack is an easier repair than an old open one. Properly repaired, the guitar can be stable for the rest of its life.

Will the repair be visible?

Depends on the crack and the approach. A glued and cleated crack is stable but usually visible up close. On higher end instruments a CA glue repair can be sanded and buffed until it essentially becomes part of the finish.

Why do cracks start behind the bridge?

As the wood shrinks in dry air, the bridge pins do not shrink with it, so they become pressure points, and cracks often run from the back of the bridge toward the tail. It is one of the most common repairs we see.

Can I prevent cracks?

Humidity is the big one. A case humidifier through the Calgary winter, keeping the guitar away from heat vents and radiators, and not leaving it in a cold car all do more than any product you can buy.

Found a crack, or not sure what you are looking at?

Bring your instrument into the shop during opening hours, no appointment needed. Assessments are free and we can usually do them while you’re here, so you leave knowing exactly what it needs. Hours and directions are on the contact page.

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