When Do you Need to Adjust the Action on an Acoustic Guitar

If you aren’t sure if your action needs adjusting or not then read on to learn when you need to adjust the action on an acoustic guitar.

This post will talk about standard string heights but this doesn’t necessarily mean that you have to stick with these heights.

If you prefer a lower or higher action that is up to you. You are only really limited by fret buzz (if you go too low) or a hard to play guitar and potential intonation issues (if you go too high).

What is Action?

When action on a guitar is referred to, it pretty much just means how high off the frets the strings sit.

A low action is when the strings are very close to the frets (compared to the normal) and a high action means that the strings are sitting high above the frets, compared to normal. You can get some idea of what is considered normal in the how to measure the action section below.

Normal isn’t necessarily best for you – some prefer different actions for different reasons – but it gives you a starting point.

The action on your guitar is usually measured in two different places – at the nut (or at the first fret) and at the bridge (usually measured at the 12th fret so quite far from the bridge really!)

What can Cause your Action to Change?

Your action can change over time for a few different reasons.

Wearing of the saddle and nut

If the material of the nut or the saddle wears down, then your action will gradually become lower and lower.

How quickly this will happen will depend on the material that your nut and saddle are made from. If it’s cheap plastic, then this will happen much quicker than it will with the likes of bone or some of the new synthesized bone equivalents (Nubone, Tusq, Corian etc).

If you are wanting your action lowered then this might sound like a good thing – but there are two reasons that this isn’t the case. Firstly, because your action is likely to lower unevenly across the strings and secondly, because this will take a long time and you want to get your action right as soon as you can.

The solution? Good quality nut and saddle. Really good quality nuts and saddles will last a life time. If you have already encountered this problem then you may need to replace the existing nut and saddle. This isn’t generally too expensive to do.

Warping of the Neck

The neck of your guitar can become warped due to humidity and temperature changes and due to too much or not enough tension from the strings.

If your neck warps inwards (has too much relief) – which might be due to strings that are putting too much tension on the neck either because they are tuned too tight or the guitar wasn’t designed to handle the gauge of strings you are using – or due to heat and humidity – then the action in the middle frets of the guitar will become higher.

If your neck warps outwards (has back bow) – which might be due to a lack of tension from strings or heat and humidity – then the action at the nut end and towards the soundhole will become higher and will become lower in the middle frets.

The solution? Chances are you will need to make a truss road adjustment to realign the neck. If this is something that has happened quickly and is due to something you can control, like string tension, then you should also make changes to prevent it reoccurring.

Sinking or Swelling of the Top

If your top sinks (usually because of the humidity being too low and your guitar drying out) then the strings will become too close to the frets and may cause fret buzz.

If your top swells (usually because of the humidity being too high and your guitar getting too wet) then the strings will be raised too high above the fret-board and may cause intonation issues and a guitar that is difficult to play.

Check this before making any adjustments to your action – if you adjust your action without first rectifying this issue then once you do rectify this issue it will be off again. So depending on whether your guitar is too dry or too wet you may have to humidify or dry it out.

How to tell when your action is too low?

The biggest tell tale sign that your action is too low is the dreaded fret buzz!

If the strings are too close to the frets then they will vibrate against the frets which causes that unwanted buzzing.

A lot of guitarists like to get their action as low as possible without getting fret buzz. It’s a fine line. And if you go too low it’s difficult to go back up without replacing parts. It’s easier to lower than it is to raise.

You can also measure your action and compare it to the “normal” below if you suspect your action is too low.

How to tell when your action is too high?

The biggest complaint that most guitarists have when the action is too high is that it makes it more difficult to play – more difficult both in term of playing fluently without errors and more difficult physically.

It requires more physical effort to fret when the action is high which means your playing is usually slower and it is harder to get your playing smooth.

It will also be harder on your fingers ad wrist because you have to exert more tension to play the notes. This will also be harder on the tips of your fingers.

The likes of barre chords are particularly difficult for a lot of players when the action is high.

The other thing that a high action can do is affect your intonation. So if your intonation is out this may also be due a high action.

If you suspect that your action is too high then you can measure it and compare it to the norms below.

How to Measure the Action

To measure your action you will need feeler gauges. We are working in some small numbers here. And fractions of a millimetre can make a difference.

Feeler gauges are a selection of thin pieces of metal (be careful the particularly thin ones can be quite sharp) of different thicknesses. Each “blade” has a thickness written on it.

Select the thickness that is close to what you are aiming for – for example you might choose a blade that is 0.26 inches (0.66mm) if you are measuring the height at the nut for the high E string (see below).

If when placing the blade on top of the fret there is still a gap then the gap is wider than the blade you have chosen. Choose the next blade up and test that one.

If the string moves up when you slide the blade in then the gap is lower than the blade you are using. Choose the next blade down and try again.

When you find the blade that will slide on top of the fret and just touch the string without noticeably moving it up then that blade represents the height of the gap.

For the action at the bridge it is usually o.k. to use a ruler or specific string action scale – the gap is larger so the accuracy isn’t as hard to get.

Action at the Bridge

The standard heights of the Low E (6th) and High E (1st) strings at the 12th fret are below. Because the low E needs more room to vibrate it needs to be higher off the frets than the high E (or there will be fret buzz).

This is measured from the bottom of the string to the top of the 12th fret (top of the fret itself not the fretboard).

Low E – 3/32 inches (.094 inches, 2.38mm)

High E – 2/32 (.0625 inches, 1.58mm)

If your action is higher than the standards here and you want to lower them check out my post on how to lower the action at the saddle end

Action at the Nut

The ‘standard’ height of the action at the nut is 0.030 inches (0.76mm) for the low E string. Though there are definitely those that have different preferences but if you want a starting point then 0.030 inches is generally considered the standard. However, a lot of players prefer to go lower than this.

This is measured from the bottom of the string to the top of the 1st fret.

The height of the other strings will differ but the shape of the nut takes care of this difference and you don’t need to worry about that unless you are shaping a nut from scratch.

If your settings at the nut are too high and you want to lower your action at the nut then check out my post on how to lower the action at the nut end 

Summary

It’s really up to you whether you want to adjust the action for yourself (you’ll need to learn a few things and will need some tools and materials) or pay someone to do it.

The safest way is to get a professional to do it. But you can save yourself some money, learn a new skill and have the satisfaction of doing it yourself too.

If at all possible I would try this first on a cheaper guitar first (if you have a higher end guitar). Though if you are only adjusting the bridge or the nut, then it’s not the end of the world if you get it wrong – worst comes to worst you’ll have to get new ones – which is a pain and a bit of an expense but not critical. So it depends on your risk aversion.

Thanks for reading and if you have any questions or comments you are very welcome to leave them in the comments section below.

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Photo Credits From Top

I, Piso17 [CC BY-SA 2.5], via Wikimedia Commons