How to adjust the string height on acoustic guitar

How to Adjust the String Height on Acoustic Guitar

Have you been playing guitar for a while? Then you will eventually need to adjust the action on an acoustic guitar. Sometimes you may have a new guitar that the string height is not exactly how you like it. Even though this is usually not the case, it’s possible the strings are either up to high or not high enough. Maybe the strings are not set just right, you will find the instrument is harder to play. You will need to adjust the string height. This article covers two scenarios of truss rod adjustments, one with measuring instruments and the other is freestyle.

Guitar string height varies among different guitar players. Blues guitar players like the strings to have some tension, where as Jazz and Rock N Roll guitarist may like a faster action. In this case you would have the strings adjusted lower to the fretboard.

Play-ability is one reason you may want to adjust the string height.  Here are some other reasons to make the truss rod adjustment.

  1. Guitar strings that buzz
  2. The neck of a guitar that is under bowed (concave).
  3. A neck that is over bowed (convex).

Why is My Guitar Out of Adjustment?

Some of the problem stems from the climate and humidity. Anything made of wood changes with climate change. Wood expands and contracts depending on the temperature and relative humidity. To help keep your guitar from warping, cracking or coming unglued, it is a good idea to get a good humidifier like the ones sold on amazon. There are humidifiers that fit in the guitar case, in the sound hole, or hang off the strings.

When a guitar becomes out of adjustment it doesn’t play good and can make all sorts of unwanted noises. To compensate for these conditions most guitars are manufactured with a truss rod. So you can adjust the string height. The truss rod runs through the neck of the guitar. From the nut at the headstock to the end of the neck. This steel bar or rod stabilizes the neck to keep it straight.

The truss rod controls the forward curvature of the neck called the relief and has a nut at one end to make adjustments. Some truss rods have a nut adjustment at both ends to adjust the tension.

What is Relief 

The guitar neck can be straight, under bowed (concave) or over bowed, also known as back bowed (convex). Due to string tension from the tuning pegs to the bridge, the neck wants to naturally pull forward. Creating relief which is the space between the strings and the fret.

The truss rod keeps the relief on the neck. By default there is a built in relief, and is a slight upward angle to cause the strings to be raised a little higher than on a straight neck. Up Bow is the name of this dimension.

You can look down the neck of the guitar to see if it is concave or convex. Turn the guitar on its side, and at eye level look down the finger board to see if the guitar is bowed. Sometimes you can hear a buzzing noise when playing . This is an indication you need to adjust the string height.

How Much Does it Cost to Adjust a Truss Rod?

Adjusting the action can seem scary, and something only a guitar technician or Luthier should attempt. Because of this some guitarists take there guitars in to have the tech adjust the string height. This is a cost that really could be averted by teaching yourself how to adjust the height of the strings. The cost of this adjustment very’s from $50 – $120 dollars, depending on where you live.

String action gauge to measure when adjust the string height

Measure the string action

If there is a buzzing noise the strut rod is tight, and if the strings are up to high then the truss rod is to lose. When adjusting the truss rod don’t over tighten it as it will strip the nut. Never turn more than 1/8 to a 1/4 of a turn at one time.

You can measure the relief anywhere on the fretboard. Measure the distance between the string and the fret using a string action gauge that can be bought on amazon, before and after the truss rod adjustment. Some guitarist just make the adjustment of the truss rod.

If the neck is to concave the action is to high. The strings will be up to high off the fretboard. This makes the instrument harder to play and a slower action. When the neck is convex the action is low, and the strings are to close to the fretboard. This can cause the buzzing noise you hear when playing.

How to adjust the action on acoustic guitar

To check the relief hold your finger on the 6th string where the neck meats the body. Then hold a finger on the first fret at the 6th string.  Use a free finger from the hand that is holding the string at the first fret. Push on the 6th string and see how much movement there is. If the string moves to much then you want to tighten the truss rod. No  movement at all then you want to loosen the truss rod.

  • A bowed guitar neck then you tighten the neck by turning the rod to the right, or clockwise.
  • If the neck is back bowed then you loosen the neck or turn the truss rod counter clockwise.

Adjusting the Guitar String Height

Some guitars have a cover over the hole for the truss rod nut. This cover will be on the headstock behind the nut. Remove the screws to reveal the truss rod nut. On some guitars the opening is at the other end of the neck, and can be accessed through the sound hole.

Pocket Truss Rod Wrenches to adjust the string height

3 Pocket Truss Rod Wrenches

Guitar kit to adjust the string height

Pro Guitar Care Tool Kit

When you adjust the truss rod you leave the strings on the guitar. Place the allen wrench or truss rod tool on the nut and make a 1/4 of an inch turn to adjust the relief. Remember clockwise tightens the truss rod and to the left loosens it. You can buy a special truss rod tool and allen wrench set at amazon.

Checking the Relief and Making the Truss Rod Adjustment

  1. Turn the guitar on its side, and look down the finger board to see if the guitar neck is bowed.
  2. Measure the string height, before adjusting the truss rod with a string action gauge.
  3. Use a percision straightedge to see if the neck is straight.
  4. Check adjustment, adjust the string height.
  5. Measure the string height with a string action gauge.

Look down the neck of the guitar, at eye level, and check to see if the neck is bowed. Looking from the tuning pegs down to the bridge of the guitar.

Using a String Action Gauge

String action gauge measure and adjust the string height

Measure the string height

Use a string action gauge to measure the height of the strings. The string action measures the distance from the top of the fret to the bottom of the string. Measure at any point by placing the gauge behind the string. The markings on the gauge are at ten thousands of an inch increments. When the bottom of the string lines up with the bottom of the mark, this is the string height at the point you are measuring. The top of the mark on the gauge is five thousands so if you line the bottom of the mark up with the string it adds five thousands of an inch to the reading.

Measuring the relief

Measure Relief use Precision Straightedge

Check to see if the neck is straight with a notched straight edge specifically used for guitars that can be purchased on amazon.
Holding the guitar as you would when you are playing it, you can use the precision straightedge to check the relief. Then check the clearance at the 8th fret. Adjust the string height. If the neck is bowed tighten the truss rod. Tighten until the straightedge lays flat on the frets. If the neck is convex then loosen the truss rod until the straightedge is flat on the frets. Measure the string height with the string action gauge.

Here are the Specs for the string action 

Listed are suggested measurements for the 1st fret and a higher fret on the low E (bass) and high E strings.

Steel String Acoustic guitar

The low E action at 1st fret .023″  | The high E action 1st fret .013″
Low E action at 12th fret .090″ | high E action at 12th fret .070″
Relief: .002″ at the 8th fret

Nylon String acoustic guitar

The low E action at the 1st fret .030″|The high E action on 1st fret .024″
Low E action at the 12th fret .156″ | High E action on 12th fret .125″

Relief: .002″ at the 8th fret


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Informational Sources Wikipedia, Stewmac