# Drywall hairline crack after taping



## Jackofall1 (Dec 5, 2010)

I am not an expert, but, I have read on this forum, written by someone that does DW, you should be using paper tape not FG mesh, and when you use FG mesh you need to use a specific compound. 

I am sure someone will chime in soon or search drywall taping.


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## stryped (Sep 8, 2009)

I bought a book on drywall. It suggested fiberglass on tapered seems with setting compund on top. Any additional coats can be all purpose. Paper tape with all purpose in corners. Butt joints always get tape. (According to the book).


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## MoldyJay (Jan 9, 2011)

There are more than one reason your seam might be cracking. You say that when you apply pressure to an adjacent sheet the crack widens... That makes me think there may not have been suitable structure to keep the wall rigid.

Can you tell me how the studs are spaced? How far apart are your screws on the seams? 

Also if there was excessive heat near the drying compound that could definitely have caused it to crack. 

I can't speak for diifferent types of compound, but where your joints are makes a difference too. Although i assume you are standing up 10s so joints should notmbe an issue in that case.

J


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## stryped (Sep 8, 2009)

MoldyJay said:


> There are more than one reason your seam might be cracking. You say that when you apply pressure to an adjacent sheet the crack widens... That makes me think there may not have been suitable structure to keep the wall rigid.
> 
> Can you tell me how the studs are spaced? How far apart are your screws on the seams?
> 
> ...


Drywall is 10 foot sheets stood up so I could eliminate butt joints. 2x4's spaced 24 inches apart for walls. Screws every 12-16 inches on seems.


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## MoldyJay (Jan 9, 2011)

Sounds like everything should be ok.. Is it only one crack near where the heat was?


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## redmanblackdog (Jan 7, 2011)

From my experience, I found that 90 minute or less fast set mud works the best over fiberglass. Fast set made to take longer, I had trouble with.

Also when using fiberglass, there has to be enough fast set over the top to give strength to the fiberglass. A skim coat won't work.

And I would have put my fasteners a little closer.

Push on the board to see if it is still loose. If not then I would either tear the tape back out and redo it or tape over the top of it.

Is that seam a cut edge to a tapered edge? It would be a little harder to do right if it was.


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## stryped (Sep 8, 2009)

redmanblackdog said:


> From my experience, I found that 90 minute or less fast set mud works the best over fiberglass. Fast set made to take longer, I had trouble with.
> 
> Also when using fiberglass, there has to be enough fast set over the top to give strength to the fiberglass. A skim coat won't work.
> 
> ...


 It is a tapered edge. The board does move a little at the joint when it is pushed on.

Crack is ROUND WHERE THE HEATER WAS and runs vertically on the seem for a couple of feet from top to bottom.


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## redmanblackdog (Jan 7, 2011)

O.K. It might be the heat. I assume that your tapered seams are breaking on a stud. So you have plenty of places to put more fasteners if needed to keep it from being loose.
The crack will come right back if all you do is put mud over it. It needs to be tore out and retaped or scraped and all loose material eliminated and taped over it.

I always use a fasting mud with 90 minutes or less setting time. But be careful, older bags that have been sitting on the shelf can set in half the time. I had trouble with other muds with fiberglass. What was the name and brand of the mud you used?


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## stryped (Sep 8, 2009)

redmanblackdog said:


> O.K. It might be the heat. I assume that your tapered seams are breaking on a stud. So you have plenty of places to put more fasteners if needed to keep it from being loose.
> The crack will come right back if all you do is put mud over it. It needs to be tore out and retaped or scraped and all loose material eliminated and taped over it.
> 
> I always use a fasting mud with 90 minutes or less setting time. But be careful, older bags that have been sitting on the shelf can set in half the time. I had trouble with other muds with fiberglass. What was the name and brand of the mud you used?


 
The white bag stuff at lowes. So I should dig a little at the crack then mesh tape over that then joint compound over that?

Since the rest of my joints have lasted about a month, and the building had been up a year before I started drywalling, is it safe to say that future cracks will be minimal?


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## redmanblackdog (Jan 7, 2011)

I would think that your other joints will probably be O.K. But remember that if that building shifts or vibrates a thin piece of fiberglass or paper isn't going to stop the building, thus cracks.

What you want to look out for now is to make sure that you don't damage the paper on the sheetrock as you remove the tape. One way is to wet the surface just enough to sink into the taped area without saturating the sheetrock it lays on. You can use a spray bottle, wet rag, or even a pass of mud. Once the mud over the tape has absorbed the moisture, then you cut into the seam and pull the tape out. Go slow and try to make sure you don't disturb the face paper on the rock. If you do, all loose material has to come out before taping occurs.

Then let dry, sand or scrape. And lay another pass of tape in and mud over that. By removing what is there (tape not so much mud), then you are keeping the tapered edge available for mud to fill over the tape, thus giving it more strength.

If you just tape over it, then you need enough mud over top of the fiberglass tape to keep it from cracking again, meaning, you may have to build your seam up, and then out if you want to hide it.

If you place your 8", 10", or 12" knife perpendicular to, and across, the seam you can see if you have to fill more or split it to hide the seam.


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