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Old 03-25-2013, 10:30 AM   #1
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But joint mesh pops in primer


This is a weird question I have not run into before. So I am doing the 6th room in our house. I finished taping (mesh), mudding, and sanding. Then I primed the room. When I did one of the but joints had what looked like mesh tape poking through. Little holes popped through the primer. I thought I had not buried the tape sufficiently. So I decided I would scrape off the paint and mud a bit so it would not build up too much. Anyway when I did I found the mesh tape was buried. I went in almost 1/8th inch and the tape was that deep. so I mudded back over the seam. The next day I noticed a hairline crack on the seam. I can push on the sheet to either side and it does not flex at all. (My hand is bruised from pushing right now). Any idea what is causing this? I was tempted to prime again and see if it went away. I tried taking a picture to show, but you cannot see the crack in the picture. I had to use photoshop to increase saturation massively so you could even see the mud over the primer (white on white) If it would help I can try to take on from a high angle which might make it visible. The stud under this joint was sistered. That is the only idea I can come up with that they are expanding slightly differently which is leading to the annoying hairline crack. It is so small you cannot see it unless you get at the right angle, but if you sand and blow the sand out it is still there (at least I think).

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Old 03-25-2013, 11:11 AM   #2
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But joint mesh pops in primer


The mesh tape!

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Old 03-25-2013, 11:24 AM   #3
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But joint mesh pops in primer


It should have been paper not mesh tape.
That drywall compound seam should be about 12" wide.
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Old 03-25-2013, 11:46 AM   #4
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But joint mesh pops in primer


To be more specific I have seen the mesh tape do what your describing many times in a lot of homes I have done remodel work in. Always use paper tape!
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Old 03-25-2013, 12:22 PM   #5
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But joint mesh pops in primer


Are you suggesting that mesh tape is always the worse choice, or that paper is just better on but joints (but not on tapered), or paper is always better? Just curious. I asked a drywall guy and he said he used mesh and did not really think it mattered much, but I have personally been thinking paper tape may be the better choice in these situations. At this point I will probably just paint again and see if a person can notice. In the future though I will definitively be using paper tape. I used it in some places in other rooms and the results have generally been better, but it was more finicky.
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Old 03-25-2013, 12:33 PM   #6
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But joint mesh pops in primer


I've been messing with houses for over 40 years and have never once seen a pro finisher use mesh tape.
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Old 03-25-2013, 12:43 PM   #7
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But joint mesh pops in primer


I agree with those above, should've been paper tape. most always, tape hairline cracks begin at bedding. sticky stuff isn't bedded, if not perfect? any adjustment sticky is gone. when coated, as mud dries and shrinks it pulls the mesh lose, sticking to mud. no way to get back under it! same with paper tape, trying to get perfect might pull all mud from under tape, coating mud will pull tape loose= hairline crack. once it's loose, it's loose no way to get sticky back. just a tiny bit of dust under mesh, no sticky coating over and over gets nothing under. if pull it loose to get under? when smoothing, the air has to go somewhere bubble. once air gets under can't get it out just move it around!

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Old 03-25-2013, 01:13 PM   #8
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But joint mesh pops in primer


Maybe just coincidence you decide. Most of what I do now is repair, in the last 2 weeks I have been to 2 homes with a total of 7 cracks. The things they had in common
all vertical cracks
all done in the last 3 years
all done with mesh tape.
done by different people.
Why I don't use mesh tape, is thicker than paper so takes more mud, whice makes it very easy to leave a hump. Since it is thicker it is very easy to sand to much mud off it, then you have those lovely squares to deal with. It has no strength vertically so cracks at the slightest movement. In my opinion mesh tape should be on the same shelf as all in one paint.
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Old 03-25-2013, 03:01 PM   #9
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But joint mesh pops in primer


yep the cost of mesh tape in the store is high and the cost of fixing the problems are even higher.
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Old 03-26-2013, 08:48 AM   #10
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But joint mesh pops in primer


I stepped on the same land mine. I see the consensus is quite clearly that the mesh is the culprit. Did not see any advice for correcting the issue however. Should this joint be excavated to the board or is there a less painful solution?
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Old 03-26-2013, 10:09 AM   #11
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But joint mesh pops in primer


What I would try is another coat of mud and feather it out farther on both sides of the seam. Probably at least twice as much as it is now and be careful not to sand to hard.
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Old 03-26-2013, 10:57 AM   #12
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But joint mesh pops in primer


Quote:
Originally Posted by ToolSeeker View Post
What I would try is another coat of mud and feather it out farther on both sides of the seam. Probably at least twice as much as it is now and be careful not to sand to hard.
Yeah the problem then is you have a high ridge build up. some of the things I have had to do was 1 cut the tape out redo with paper and sand etc.. at least this happened before any texture and real paint was used. a good skim coat will help as well. and that is another reason why I won't do vertical drywall. the house settles and pop goes the seam long after the contractors are gone.
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Old 03-26-2013, 05:46 PM   #13
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But joint mesh pops in primer


"Are you suggesting that mesh tape is always the worse choice, or that paper is just better on but joints (but not on tapered), or paper is always better? Just curious."------------------------------ Mesh tape stretches to show a crack, paper tape doesn't;

"In the case of paper tape, approximately 30 lb./lin. in. of tensile force (pulling apart) is required to break the
tape with no measurable movement or elongation (no stretching). On the other hand, glass-fiber tape elongates
(stretches like a rubber band) 0.03" before reaching maximum or breaking load of 70 lb./lin. in.
Research investigation has shown that hairline cracks or nail pops are visible at 0.01" of movement with
veneer plaster system joints treated with glass-fiber tape. Actual load at that amount of movement is only
20 lb./lin. in. or about 30% less than the breaking load of paper tape (with no movement). As such, paper tape
provides greater joint strength and is recommended where greater movement and shrinkage is anticipated.
The performance of glass-fiber tape is somewhat improved if the tape is prestressed or stretched slightly during
its application and imbedment with the veneer plaster. The prestressing is accomplished with the presetting
because as the veneer plaster sets, it expands and furnishes the movement necessary to stretch or prestress
the tape, thus increasing its immediate resistance to load (tensile forces). The amount of expansion provided by
the plaster is dependent on the rate at which the plaster sets. With rapid-drying conditions (see graph), the
plaster expansion will be significantly reduced resulting in no tension (prestressing) in the glass-fiber tape,
thus reducing its ability to control cracking.
Paper Tape Application Techniques The Sheetrock joint tape and Durabond or Easy Sand joint compound method is unaffected by rapiddrying
conditions and achieves maximum joint strength (about 30 lb.) when dried. The setting-type compound
is recommended, because once it is set, it remains stable, even when troweling the wet coat of veneer plaster
over it. If a drying type of joint compound were used, it would be rewetted by the plaster application causing
movement of the tape resulting in distortion of the finish surface and possible loss of joint strength."
From: http://www.usg.com/rc/technical-arti...ems-en-PM5.pdf Granted, that was plastering but still applies. Notice as it re-wets with additional coats/texture, it can then crack anew.

So you were doomed from the get-go with the mesh tape and a second (possible) doom; if you used sistered lumber that was new (rather than old)- MC of 19% that will dry to 10% and crack then; pp. 11, 12; Another reason to use the shortest required fastener, rather than a longer one.
https://docs.google.com/viewer?a=v&q...fHFsk1RrK9G2HQ

Fastening it off is similar to laying sub-flooring;
"5.6.1 Starting at the center of the gypsum panel product, the
first set of nails, shown by solid dots, shall be applied in row
1 first, then in rows 2 and 2A, then in rows 3 and 3A, then in
rows 4 and 4A, etc. Nailing shall always proceed from the
center to the ends and edges of the gypsum panel product."
From, and any other questions unanswered, lol; http://www.lafargenorthamerica.com/G...%20English.pdf

The third doom (possibly); using a "drying" compound rather than the required "setting" compound for the mesh tape embedding;
"Drying Versus Setting
Drying-type compounds, which contain water, must be allowed to dry completely in order to ensure creation
of a strong joint. The time needed for thorough drying may not be available in an assembly-line environment. If finished sections are moved before joints have dried completely, cracking may result. Drying type compounds are available in both powder and ready-mixed forms. They can only be used with paper tape.

Setting-type compounds harden chemically for quicker finishing and joint strength, and are available in a variety of setting times. This makes them especially suited to assembly line production. They can be used with both paper and fiberglass joint
tape."
From: http://www.usg.com/rc/installation-a...-en-MH1216.pdf

Gary
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Old 03-26-2013, 07:13 PM   #14
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But joint mesh pops in primer


Most drywall mesh tapes clearly state on the packaging "setting type compound only".
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Old 03-26-2013, 08:02 PM   #15
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But joint mesh pops in primer


Quote:
Originally Posted by ToolSeeker View Post
What I would try is another coat of mud and feather it out farther on both sides of the seam. Probably at least twice as much as it is now and be careful not to sand to hard.
Ok so I ended up just doing this. I primed and there was no more of whatever the heck that was. I painted later in the day and after that I could still kind of see something there, but it looks more like a hint of the seam (no crack) and it might fade with a second coat of paint or time. Might just be the result of changes in how much absorbed. Anyway I am happy enough with the result. I will definitely keep the issues with mesh tape in mind. I actually had some good luck in the past with mesh tape. I had a crazy corner (45 on the ceiling) that I probably did all wrong in my first room b/c I could not figure out how to attach two sheets well the the roofing member that was not modern dimensional lumber (all wavy and stuff). I ended up with a strip of metal screwed in to hold the drywall down then built the corner way up with layers of mesh tape. It has held up well and looks nice, very crazy though.
Quote:
Originally Posted by Gary in WA View Post
The performance of glass-fiber tape is somewhat improved if the tape is prestressed or stretched slightly during
its application and imbedment with the veneer plaster. The prestressing is accomplished with the presetting
because as the veneer plaster sets, it expands and furnishes the movement necessary to stretch or prestress
the tape, thus increasing its immediate resistance to load (tensile forces). The amount of expansion provided by
the plaster is dependent on the rate at which the plaster sets. With rapid-drying conditions (see graph), the
plaster expansion will be significantly reduced resulting in no tension (prestressing) in the glass-fiber tape,
thus reducing its ability to control cracking.
Paper Tape Application Techniques The Sheetrock joint tape and Durabond or Easy Sand joint compound method is unaffected by rapiddrying
conditions and achieves maximum joint strength (about 30 lb.) when dried. The setting-type compound
is recommended, because once it is set, it remains stable, even when troweling the wet coat of veneer plaster
over it. If a drying type of joint compound were used, it would be rewetted by the plaster application causing
movement of the tape resulting in distortion of the finish surface and possible loss of joint strength.&quot;</i> From: http://www.usg.com/rc/technical-arti...ems-en-PM5.pdf Granted, that was plastering but still applies. Notice as it re-wets with additional coats/texture, it can then crack anew.

https://docs.google.com/viewer?a=v&q...fHFsk1RrK9G2HQ

The third doom (possibly); using a &quot;drying&quot; compound rather than the required &quot;setting&quot; compound for the mesh tape embedding;
&quot;Drying Versus Setting
Drying-type compounds, which contain water, must be allowed to dry completely in order to ensure creation
of a strong joint. The time needed for thorough drying may not be available in an assembly-line environment. If finished sections are moved before joints have dried completely, cracking may result. Drying type compounds are available in both powder and ready-mixed forms. They can only be used with paper tape.

Setting-type compounds harden chemically for quicker finishing and joint strength, and are available in a variety of setting times. This makes them especially suited to assembly line production. They can be used with both paper and fiberglass joint
tape.&quot;
From: http://www.usg.com/rc/installation-a...-en-MH1216.pdf

Gary
Thanks for all that. The guy I talked to did use setting type compound with mesh tape, and I did use drying type compound... oops. Anyway things are ok except for that one seam in that and the other rooms, so I will just take my good luck and be happy.

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