Nail pops at the base of vaulted ceiling-no roof leak

(Kenton Shepard, CMI) #1

Two homes with the same condition- nail pops at the base of a vaulted ceiling. Both at 8000 ft. in CO. Both homes had kitchens open to the effected room. Both homes less than 10 yrs. old with good roofs. The last had Ice & Water Shield at the roof edges as insurance against damage from ice damming.
Pops were on the ceiling a few inches above the ceiling/wall junction. No stains. No other nail pops anywhere. The effected rooms each had a ceiling fan.

My theory- during the winter, air carrying moisture from the kitchen is pulled up the wall by air currents created by the ceiling fan. That part fo the roof may be low on insulation so that when moist air reaches it, condensation forms, raising moisture levels in the drywall mud enough to cause the nail pops.

Nail pops- I know that metal expands by a factor of about 17 as it turns to rust. Is this what pops loose the mud covering the nail?

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(Paul Hinsperger, CMI) #2

I think it just has to do with the low insulation levels at that point. Moisture already in the wood freezes and pushes the nail out.

Similar from what you described except the origin of the moisture and the rust.

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(Raymond E. Wand) #3

I think its the differential temps in the roof joists, not moisture related per se. The wood expands and contracts, thus the nail pops. I believe this is why screws should be used.

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(Brian A. MacNeish) #4

Typical cases nailpopping happen when drywall is applied to lumber with higher humidities, more likely to be above 19-20% moisture content with a fair amount of shrinkage to occur as the house dries. When the wood dries and shrinks, a small gap is left between the back of the drywall and the stud. When a bit of force is applied to the face of the drywall, the nail/screw head pops out the filler/paint.

I'm wondering: as these houses dried and shrank, the wall drywall panels pushed the cathedral drywall back up against the rafter/truss which caused the typical nailpop. On the rest of the upper slopes, the gap exists but the drywall is hanging on the nail/screw heads and has not been pushed up, hence no pops.

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(homebild) #5

The nail pops are lkely the result of structural deficiencies.

1st, you have perhaps 70psf or greater snow loading conditions.
2nd, you have cathedral and vaulted ceilings in place which appear to be under-engineered for the conditions.

Seems to me that what is occuring is that the ceiling rafters are over-stressed for loads and conditions and bending excessively under load.

As the bearing wall(s) push out from overloading, the nails 'pop' near their rafter connection to such walls.

Structural defect if you ask me.

Undersized rafters for the loads and spans.
No cross-lateral connections to prevent bearing walls from spreading under load.

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(Brian A. MacNeish) #6

Nailpops have never usually been connected with structural failure but just an aesthetic deficiency. Kenton mentions no cracks in drywall and none were visible in pictures......these I would expect if the place was moving.

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(Raymond E. Wand) #7

[QUOTE]
2nd, you have cathedral and vaulted ceilings in place which appear to be under-engineered for the conditions.
[/QUOTE]

How do you know that? All from a picture and nail pops?

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(Roy D. Cooke, Sr) #8

I expect the homes built at different times of the year.
More moisture in the wood led to more shrinking.
I would say screws on both sides of the nails repair and paint .
I would be surprised if there was any more nail pops.

.......... Cookie

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(Kenneth Lott, 001236461) #9

It could be the same forces that cause truss uplift. The rafters get longer in winter due to the cold moist air and because they are fastened at the birdmouth and the ridge beam, they bow up in the center.The drywall hanger puts up the ceiling first, the bottom edge of the ceiling drywall,where it meets the wall, hangs up and does not follow the upward movement of the rafter when it bows. When the rafter returns to its original shape and size in the summer, it retightens up on the nail, when the rafter comes back down it pops the mud off. I bet if you could get to the back side of the wallboard, you would see the rafter seperated from the top plate. It doesn't take much movement for this to happen.

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(David A. Andersen, TN HI# 40) #10

My assessment is that the nails are too close to the ceiling/wall juncture.

The closest nails should be 7 to 8 inches away and double nailed. This creates a floating angle.

Cathedral ceilings move a lot. When the sheet rock is attached directly to the roof rafters this condition is accentuated. If the nails are further away from the juncture, there is room for the sheet rock to flex and there is a lesser chance of the nail to pop.

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(Roy D. Cooke, Sr) #11

If a home has truss uplift an easy way to hide it is put trim around the exterior and only fasten it to the ceiling.
This allows the ceiling to move up or down as the season changes and you never see a crack as the trim also goes up and down.

. Cookie

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(David P. Valley) #12

Nail pops are a common occurance in all new construction and are basically a simple fix.

As many have already stated here, it's simply the high moisture content in the lumber. Framing lumber used in new construction often shrinks after it is installed. Kiln dried lumber often has a moisture content that ranges between 15 - 20 percent. The moisture content can drop to 10 percent after installation.

Also, if there's a lot of rainfall during the rough framing and the lumber is stored outside and not covered up, some builders typically do not wait for the framing to completely dry before the drywall is installed. Now you've got moisture laden framing that'll take longer for the drying process, causing nail pops as it dries.

Another common cause of nail pops is "operator error". The drywall installer fails to push the drywall firmly against the framing lumber as it is being fastened. This failure results in a small void space between the back of the drywall and the framing lumber. If someone or something pushes against the drywall, the drywall pushes back into the gap and the nail pushes right out to the surface.

If framing lumber is allowed to dry properly and drywall screws are utilized, nail pops will likely not occur.

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(Kenton Shepard, CMI) #13

No sign of foundation movement. The homes were both new enough to have had modern engineering and look typical in rafter size.

Although it's real dry here, lumber (especially studs) gets unloaded from flat cars at the lumber yard soaking wet and wrapped in plastic. It's often taken to a jobsite right away where they pull off the plastic and use it to build with. Dry air... wet lumber... definitely some shrinkage there. This in addition to the typical settling due to gaps at framing connections.
Thermal expansion and contraction onlone could contribute too.

After the first year or two the lumber would probably have reached moisture equilibrium content with the environment and have finished shrinking, so damage is probably from the first year or two and shouldn't be ongoing.

So if the studs shrink, but drywall doesnt, wall drywall pushes up and closes any gap behind the ceiling drywall, popping nails. If there was no gap created by the guys doing the hanging, rafters might expand when they freeze, leaving behind a gap after they dry and shrink.

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(homebild) #14

  1. Location. Colorado is generally a very high snow load region.
  2. Presence of cathedral and vaulted ceilings.
  3. Lack of any structural cross laterals to hold opposite bearing walls together and keep them from spreading

Basically what can happen under excessive load, and from undersized rafters and cathedral or vaulted ceilings that do not have any cross lateral bracing is a similar condition to 'truss lift' as another member already mentioned:

The center of the rafter moves down and the ends move up.

It is the ends moving up that can cause nail pops in the symptomatic manner described.

Also, nailpops are becoming much rarer in newer contruction as building codes allow fewer fasteners to be used when adhesive is used. Most contractors opt to use adhesive and fewer fasteners , except where requried, and these fasteners are required at the ends or edges of boards....right where these pops occur.

Personally, I would check for structural defects like undersized rafters for the spans first, and only then consider other causes once structural causes are ruled out....and unless you can have an engineer rule them out...you'd better consider structural causes.

It may be nothing and may be simply the use of wrong type fasteners, moisture in the lumber, or other less dramatic causes...

But structural reasons should not immediately be ruled out in this case and should be your first causation item to investigate.

JMHO

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(Marcel R. Cyr, CMI) #15

Was it ever verified that the installation was with screws or nails?

Just curious before I give my two cents. ha. ha. ;)

Marcel :)

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(Michael Davis) #16

I have been building houses for the last 8 years and now new to home inspections. I have seen this happen in homes that are new. I would have to agree with the other guys on the expansion and contraction of the materials and not moisture, if it were a bathroom however I might consider that as a possibility.

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(Brian A. MacNeish) #17

Drywall nailpops in new construction are almost always caused by wood shrinkage although the installer can be a bit slack and this leads to popping also.

From a building website:
"Nail pops can occur for a variety of reasons. One common cause of nail pops is 'operator error'. The installer fails to push the drywall firmly against the framing lumber as it is being fastened. This failure results in a void space between the back of the drywall and the framing lumber. If someone or something pushes against the drywall, the drywall goes in and the nail pushes to the surface.

However, lumber shrinkage can create the same identical effect, even if the drywall was properly installed. Because shrinkage causes the greatest dimensional change along the lumber's width, a void area can develop between the drywall and framing members."

Expansion and contraction of materials are caused by (1) uptake and release of moisture and (2) heating and subsequent cooling of the material.

You have ruled out the moisture related shrinkage caused when materials dry out so the expansion/contraction caused by heating/cooling must be the culprit. This should be a yearly phenomenon due to the extreme temperatures of winter/ summer at this location.

The nailpop caused by drying shrinkage is a one time effect and does not return after the screw/nail is fully driven and the surface re-finished. The yearly expansion/contraction means the surface cannot be finally finished as it will just comeback again in 6 months again when the other temperature extreme is attained. This is what happens with the phenomenon of "truss uplift"......you can hide it at construction or later on but it will always occur (as long as we need high levels of insulation for energy conservation).

SO......if the nailpops were repaired once and never come back.....drying shrinkage would be the problem. If they came back yearly, expansion/contraction by heating/cooling would be the problem.

If there was a structural deficiency and movement due to lack of collar ties, the effect at this cathredral style ceiling/supporting wall intersection would be a stress crack along the joint, not the odd nailpop.

My money's still on the drying shrinkage!!

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(Marcel R. Cyr, CMI) #18

I posted this on the similar subject.

http://www.nachi.org/forum/showthread.php?t=2892

Marcel :) :D

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(Gary L. Porter) #19

Correct David

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(Brian A. MacNeish) #20

Marcel:

In the following, I quote from one book , Drywall Application, *of a 13-14 book *Builder's Series put out in the mid 1980's by Canada's national housing agency, Canada Moprtgage and Housing Corporation. If there is excessive moisture and air humidity in a building, the condition may lead to sagging or wavy ceilings in properly installed drywall. No where do they mention excessive interior moisture as a cause of nailpops.

Their format is as follows:

PROBLEM- Sagging or wavy ceilings

CAUSE - Excessive moisture and humidity
Texture spray too wet; high humidities (my ed.- from spray painting)* and poor ventilation during construction; moisture in attic. Moisture absorption will soften the gypsum core.*

PROBLEM- Nail pops

CAUSE - Wet framing lumber
Framing lumber should not exceed a moisture content of 19% (the maximum allowed by the National Building Code). However, in many parts of the country, and particularly in Eastern Canada, the moisture content of framing lumber is often much higher. As this lumber dries to 12-14% (6-9% in mid-winter and in drier climates) shrinkage occurs , the stud pulls away from the gypsum board, and any subsequent movement of the board causes the nail to "pop". A 10% change in moisture content can cause a spruce or fir stud to shrink up to 1/4"

CAUSE - Misaligned or warped studs

CAUSE - Fastener length or type
Longer fasteners actually worsen the problem of nail pops, since shrinkage takes place over a greater length of nail.

CAUSE - Fastening techniques
It can be difficult to hold the board and nail at the same time. Thicker insulation often prevents good contact between the board and framing.

CAUSE - Vibration
Exterior fastening of brick ties, siding or trim can loosen drywall nails

See:
http://www.waltersforensic.com/articles/civil_engineering/vol6-no1.htm

From this article:
"The mechanism for ceiling pops can be related to shrinking of the top and bottom wall plates, which forces the drywall on the wall against the drywall on the ceiling, again causing the gap between the face of the wood framing member (in this case a ceiling joist or truss) and the backside of the drywall to close, forcing the head of the fastener through the face of the ceiling.. Truss uplift can also cause movement of the ceiling, causing popping, as well as other problems. Popping caused by either of these mechanisms usually occurs at the perimeter of the room."

The highlighted text seems to confirm my theory stated in an earlier post!!

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