Need more neck relief!


You had this problem last year, if I recall correctly. Being the owner of guitars that all have unfinished maple necks, I say again: you have to get the humidity in that room between 35-40% and keep it in that range. I don’t care how drafty the room is, you can do it. And it’s not the insulation or leaky seals (those are probably helping a little bit), it’s the dry heat being pushed into the room that is driving the humidity down. Buy a humidistat for $10 to $20 and minimize fluctuations as much as possible. Finished necks will react more slowly, but as you can attest will still dry out and start to fight against the non-organic material in the neck—truss rod, neck, nut, etc.

You are correct about the humidifier too. Buy one that is evaporative. Depending on the design and the content of your water, you might develop some scaling issues from the stuff left behind. There are some quick solutions, if you google. I personally use good ole vitamin c that you can buy in bulk on amazon. But I believe some people also use vinegar and other natural solutions.

Put open containers of water on your heat source as well—this is a free solution that can help a little bit but will not be a stable solution. An old pot on the radiator is that’s what you have; a glass on the vent if you used forces air. Whatever it is, the water will evaporate into the room slowly and naturally.

Also, the same cuts the other way. If you get a ton of moisture in the summer because if AC, the you need a dehumidifier. Our house for example can have humidity over 60% when temperatures rise. This is actually harder to control, in my opinion, because even good units have a tough time removing humidity from cold air and keeping things under 55-60%, but a good dehumidifier can keep things right where they need to be.

Hope this helps.


Hey Troy, yes NYC is brutal on all my instruments. I would highly recommend keeping acoustics in cases with dampits. Also a humidifier but you are already on that. In my experience when it gets dry the wood shrinks and necks get more bowed, whereas when it gets humid they get straighter. Meanwhile the opposite is true with the body, on acoustics when it gets dry the top sinks lower making the action lower. When it gets humid the top expands and bulges our making the action higher. It also seems to happen a little on electrics, despite being solid wood and metal bridges. But certainly the guitar dimensions change a little even on electrics. One trick for a truss rod that is all the way tight but the neck is still bowed is to take the truss rod nut off and insert a washer in there and put the nut back on. Then you get a bit more tightening range. But this sounds like the opposit of your problem.


It arrived today! Unlike the slick computerized ultrasonic one, it’s basically just a bucket with a fan in it. But it works quickly here in the office, which is relatively decently sealed. Brought the whole place from 30% to 45% in probably less than an hour. The trick will be seeing how well it works in a drafty house. Here’s the one we got:

It certainly is! I spent some time checking out expensive humidifed cases just because I assumed the leaky bucket we live in would prevent humidifiers from working well. But who knows - we’ll see.


To add to the fun of my studio in an old cow shed, a mouse appears to have eaten its way in through the roof insulation. Well, it started on the insulation, now it seems to have moved on to nibbling the ancient wood that holds the roof up.


Fellow NYC resident here.

I have a pretty nice Air-o-Swiss humidifier that I keep going during the dryer months, aiming to keep humidity at home around 45%, and my guitars are generality fine. I have a practice space up in Greenpoint that gets a little dry, but I don’t keep any of my nicer gear there.

You should know the NYC radiator trick -
If you have old-school metal radiators that you can’t control and are either off or 90 degrees (common in NYC), a good hack is to keep metal pans of water on top of them. The water evaporates and humidifies the air. You’ll be amazed how fast it evaporates.

Back to the top post, if you have 12s pulling on your neck and the truss rod is slack and your neck still doesn’t have relied, you’ve got some back-bow problem happening with the neck, or maybe a problem with the truss rod. From what I can tell, Dan E is pushing the neck into relief and then tightening the truss rod to hold it there.

As @Troy suggests, he’ll need to do the reverse, but I think will only be possible if you have a double-acting dress rod that can push the neck intro relief -f it’s an older guitar, the single-acting truss rod is likely only capable of applying backwards pessure to counter-act string pull.

The cure for this is more involved - essentially forcing the neck into some backbone with clamps and applying heat and trying to coax it into “sticking”. I’ve also seen it solved on vintage guitars with more extreme measures involving removing the fingerboard, and working the maple neck with the truss rod removed.


How’s it working? How drafty the house is shouldn’t prevent the humidifier from keeping things relatively stable—just might have to refill the water a bit more frequently.


That’s probably the case here. If I can clamp into relief, then set the truss to pull it back, that would be cool. I’d like to have the truss be somewhere in the center of its range of travel, so I can effectively move it in either direction. From the sound of it that may not be realistic.

Hard to tell, we just dropped back into the thirties again yesterday so I only have a day and half with the humidifier. But it ran through four gallons of water overnight, ran the tank dry, and then the house dropped back down to 21 percent by the time we got up. Filled it back up and running it set on 45% as I type this so we’ll see.

I suspect that even once all the wood in the house gets saturated, we’re still going to have a situation where this thing will need to run hard all the time on really cold days to keep things stable. It’s an old, drafty house and that may just be the way it is. Maybe we’ll get another one so the refills are less frequent. Who knows.

We’ll see!


Are you humidifying the whole house or just your studio? If just the studio, that’s crazy! I stand corrected. That is a massive fluctuation for a few hours. It would take a week of very cold days in addition to using the fireplace for the humidity in my house to drop that much. Can’t get my head around that. My guitars would be unplayable.



Typically in the dry winters, the neck should go into a forward bow aka more relief.

I see two observations:

You saying it “goes totally straight”
You hearing it buzz.

Considering the guitarist you are, I trust the latter, and that brings me to:

It’s probably buzzing but for the opposite reasons. It’s actually probably gone into excessive relief, reducing next fret clearance and thus contributing to buzzing. Counter-intuitive perhaps, but ceteris paribus, a lower relief or flatter neck will result in a greater next fret clearance, which is the answer to buzzing, considering your frets are relatively level.

There are some very rare cases in which the wood moves the opposite way- that the neck becomes reverse bowed under dry winter weather, but my reply does not pertain to that rare example.

If you could give me a general reading (numbers, descriptions) of the neck relief (press first fret and 16th fret and I need a reading of a gap in the 7-8th fret area), action height, and general state of frets, I’d be able to give you more specifics.

Hopefully you get it sorted out. A humidifier is a good thing not just for guitars but people like me who hate the dryness and its effects on my sinus.


Can you explain why this happens?


Typically wood retains its original shape best around 40-50% relative humidity (and 25 degrees C ideally).

What happens in low humidity (characteristic of dry winters) is that the wood is no longer in that state, and the wood, trying to maintain equilibrium with the surrounding, shrinks because it’s losing moisture. It’s small but it’s enough to cause a difference. That’s why frets “sprout” and in many cases the neck caves in the middle likewise as a loss of this wood volume. The adj. truss rod was invented to counteract and balance weather extremes so that we don’t need to play guitars in such ideal conditions all the time. As to why exactly it caves in the middle, wood tends to have this “cupping” effect that can be best explained by a wooden dish/disk that takes on a slight concave “U” shape at either end during dry seasons- primarily due to the grain orientation.


Thanks. The changes in the wood I think I understand, it was the direction I was wondering about: Why does dryness lead to more relief instead of less, i.e. why does the neck bend forward and not backward?

The grain in a guitar neck generally goes lengthwise, which, if I understand cupping correctly, means that the cupping effect would tend to warp the neck crosswise, not lengthwise.

Now that I think about it, it seems more likely that the directional asymmetry is provided by the string tension, which I missed because I was thinking about the effect of temperature and humidity on wood, and ignoring the strings altogether in my mental model.


Apologies for the late response. Let me amend my explanation, although the general correlation of low humidity and increased neck relief still stands.

Humidity affects the volume of the wood but not the truss rod (outside the quantum world), and when wood shrinks, the pressure exerted by the rod on the wood is less, hence the forward bow. In the reverse case of high humidity the wood swells, resulting in the pressure applied by the rod to the wood to increase, hence reducing the relief. Kind of nature’s way of “loosening & tightening” the rod, even though the rod itself isn’t being loosened or tightened.

This is most often the typical case, and the cupping effect should apply to statistical outliers- and could be an explanation for neck twist or necks moving the opposite way as normal, but isn’t too relevant here so you’re absolutely right within the context.

Not sure if I understand your idea of directional asymmetry correctly, but assuming a 010 gauge set of strings, the tension on each string is relatively the same either way. The string tension is only secondary to the primary forces which describe how the changing size of the wood and truss rod effect concavity in the neck, meaning even without the strings, the concavity will still exist just to a lesser degree since the strings aren’t affecting it yet. In other words, the force exerted by truss rod on wood (and wood on truss rod) is always there, though once you put the strings on it can compound this effect (ie. low humidity neck leading to less pressure on rod leading to a concave area in the middle which is further compounded by the string tension).

Ex. if you observe with a straight edge the state of the frets before stringing a guitar (assuming the frets are a good proxy for the straightness of the board itself) and it’s observed to be .010" in the middle, then it’ll only result in more relief with strings on, and almost unplayable by then. Likewise, if you take the strings back off the concavity will be reduced, but it will still be there (or even go into a back bow- since I like my necks with zero-relief once strung up).


If you get no satisfaction with the humidification solution, I would attempt the oven approach on one guitar and see how well it works for you. Never attempted it myself, but the logic seems sound. With the oven approach, you want to soften and reset the glue in such a way that the fingerboard itself ends up permanently applying slight bowing tension to the neck. I think the hard part is finding an oven big enough, even for a removed bolt-on neck. I’d be leary of the heat gun, as I think it would be difficult to raise the temperature evenly along the entire length and width of the neck/fingerboard interface.


I wonder if shimming on the headstock side of the underneath the heel would help this.


This makes sense but for whatever reason it is the opposite of what is happening to me. In the summer, with humidity, things were ok. As soon as it got colder and drier, the buzzing started on all strings. So I measured it then, with a first fret and 17th fret press, and there was no gap - metal on metal. I loosened the truss all the way until the nut spins, and now I have about .010 with both frets pressed. The upper strings still buzz a small amount, but I think that’s a fret issue - I just noticed that they’re all a little dented so I probably need a fret job.

Humidifying both, both are about the same size, and we have the same unit in both places. At work we can get to 40% in an hour or two with the fan on high, and it runs intermittently after that. If I top up the humidifier when I leave, it’s still 40% in the morning and there’s still some water left in the tank. At home, the single unit has to run continuously with the fan on high to reach about 38% humidity downstairs and 27% upstairs. If we shut it off at all, like to watch a movie without fan noise, it reads 20% in both places when we’re done. That’s this week - it will be worse when the temps drop further. It’s just a super old place full of holes.

If we close up the downstairs doors and abandon the upstairs, the unit can do 40% with the fan on medium. So I think the big leak is upstairs. So we’ll just stash the instruments downstairs with the doors closed or open with the fan on high. Could be worse I suppose!


Good idea though it is a roundabout way of affect the feel, but I’m wary of suggesting it because:

  1. it doesn’t affect relief directly
  2. some don’t like the idea of it
  3. it’s primarily to take care of neck angle issues/preferences, which troy isn’t dealing with here.

But you reminded me of something that I’d wanted to do for some time :slight_smile:


That is indeed odd, but there is also another aspect.

I realized I prefaced it with humidity not affecting metals noticeably, but with lower temperature, rods do shorten a miniscule degree, which would straighten out the neck theoretically, which is basically “tightening” again, but to what degree is different for each guitar.

Are your fret ends poking out this winter?


If the wood of the neck is flat-sawn/plain-sawn, loss of moisture can potentially cause it either to bow, or back-bow, depending on the geometry of the grain relative to the plane of the strings.

Will Gelvin is a polarizing figure in youtube-guitar-land, but the information in the video below about the potential effects of wood grain geometry on guitar necks is very useful:


This is the cupping effect we discussed above. Unless the neck is crosscut (which I’ve never seen), this would only very rarely cause neckbow in either direction. It’s far more likely to cause twisting or distort the neck cross-sectionally (i.e. distort the fingerboard radius or create odd bulges, etc.)