# Drywall cracks at joints



## whynot (May 21, 2014)

I'm new to drywall, and doing a job of 100 sheets in a room over garage as I had time, so several delays. Walls are 8' @24oc with 8' 1/2" rock hung vertically (12' wouldn't go up stairs and no butt joints). Ceiling is 16x60 2x4 truss 24oc with 1x4 perpendicular runners @ 16oc, with 8' 1/2" rock that runs perpendicular to the 16oc. Butts end on 1x4 centers. All 1x4 screwed to truss and all rock screwed to 1x4 @ 6-7" (but no glue... probably my first mistake). All joints are tight, worst is 1/8" (no crack there) and paper taped with USG greentop all purpose mud using Homax 6500, rolled corners and flushed. Bedded flat joint tape with 4" knife, making sure mud left under, and that enough mud squeegeed out to insure no dry joints then boxed, etc. Tape dried before next coat. One coat each day was finished with USG ultralightweight (olive greentop). Worked on this project over a period of several weeks. All perfect, not a crack. Painted with PYA primer and the next day, had cracks at a few ceiling joints, but no cracks in walls or corners. Nothing drastic. Painted last night with Valspar ceiling white and this AM, man do I have cracks. My concern is that it sat for probably two weeks w/o a crack then painted and boom, cracks. Coincidence or something related to painting? What did I do wrong? ... and I was so pleased with my adventure into this trade. Can't find my seams that aren't cracked, so I at least got the finishing right.


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## MrWillys (Mar 10, 2014)

whynot said:


> I'm new to drywall, and doing a job of 100 sheets in a room over garage as I had time, so several delays. Walls are 8' @24oc with 8' 1/2" rock hung vertically (12' wouldn't go up stairs and no butt joints). Ceiling is 16x60 2x4 truss 24oc with 1x4 perpendicular runners @ 16oc, with 8' 1/2" rock that runs perpendicular to the 16oc. Butts end on 1x4 centers. All 1x4 screwed to truss and all rock screwed to 1x4 @ 6-7" (but no glue... probably my first mistake). All joints are tight, worst is 1/8" (no crack there) and paper taped with USG greentop all purpose mud using Homax 6500, rolled corners and flushed. Bedded flat joint tape with 4" knife, making sure mud left under, and that enough mud squeegeed out to insure no dry joints then boxed, etc. Tape dried before next coat. One coat each day was finished with USG ultralightweight (olive greentop). Worked on this project over a period of several weeks. All perfect, not a crack. Painted with PYA primer and the next day, had cracks at a few ceiling joints, but no cracks in walls or corners. Nothing drastic. Painted last night with Valspar ceiling white and this AM, man do I have cracks. My concern is that it sat for probably two weeks w/o a crack then painted and boom, cracks. Coincidence or something related to painting? What did I do wrong? ... and I was so pleased with my adventure into this trade. Can't find my seams that aren't cracked, so I at least got the finishing right.


My guess would be you wiped the tape to tight and forced the mud out. All purposed does not have as much adhesion as taping mud, so always try and use taping for paper tape, and topping for floating joints for less shrinkage.

All cracks must be cut open and retaped.


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## thefinisher (Sep 2, 2011)

Seems to be some sort of movement going on that may not be your fault. Either way I would put fibafuse tape over the cracks and re-finish them. This is not self adhesive tape. Look up fibafuse paperless drywall tape. The good thing about it is you can give it a couple tight coats then sand it down. The fiberglass will start sanding off if you go to far unlike paper which will fuzz up.


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## Mudstar (Feb 15, 2008)

I think ultralightweight compounds are a big part of your problem....JS


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## fr8train (Jan 20, 2008)

I/we use lafarge rapid-coat. Doesn't get much lighter.


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## fenez (Nov 30, 2009)

fr8train said:


> I/we use lafarge rapid-coat. Doesn't get much lighter.


Big thumbs up for lafarge rapid coat...nothing comes close.


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## Corey The Taper (Mar 18, 2014)

Never heard of that is that like easy sand or durabond


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## fr8train (Jan 20, 2008)

No, it's a pre-mix compound.


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## fr8train (Jan 20, 2008)

In my experience, VERY low shrinkage and sands like a dream.


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## Corey The Taper (Mar 18, 2014)

We only get usg and the cheap **** from lowes think its called easy finish. I only use usg green lid for every coat


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## fr8train (Jan 20, 2008)

Lowe's around here carry it


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## endo_alley (Nov 2, 2013)

You probably did not meticulously cut out the loose paper at factory edges, Lightly V the butt joints, and prefill with setting compound prior to taping. The tape may not have been centered on the joints. And as previously said the mud may have been pushed too hard. Maybe not thinned properly.


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## forestbhoy (Jun 16, 2013)

fr8train said:


> I/we use lafarge rapid-coat. Doesn't get much lighter.



Its now g tec over here and i use the bag stuff ( cost as per usual) . A bit of a bugger to get the hang of knocking it up, but when you do,lovely to spread with little shrinkage and you could sand it with a wet wipe...:thumbsup:


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## Alajay (May 29, 2014)

*Drywall cracks*

If your ceiling is continuous 60ft the I would think it is from movement. You need to have a control joint installed every 30ft maximum. It doesn't matter if your drywall is installed on wood, metal, or suspended grid. It will crack without them.


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## Pd67 (Jan 19, 2013)

"Painted with PYA primer"
Was that PYA or PVA. I wouldn't prime with pva on new drywall.


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## whynot (May 21, 2014)

Thanks for all the replies, below is a follow up.

1. Yes, 60 foot walls/ceiling continuous. Hmmm, never thought of expansion joints, but worst crack parallel at 4' from end wall. Would have thought more toward middle. But, the obvious question is how to have a smooth 60’ ceiling with an expansion joint? What are they or are we talking simply a molding strip, or architecturally pleasing change in direction, etc?

2. I must have been hungry and thinking of PYA Monarch food co. I meant PVA which is supposedly high solids for new sheetrock surfaces to help blend the absorption difference between mud and rock as I understand it. Seemed to have done the trick anyway.

3. Thanks for the advice on all purpose vs taping and topping mud. I will certainly look into that next time.

4. Cracks seem to come and go (ie more or less) so yes some movement is possible, and again expansion may still be an issue too. Of course here in SC, humidity is coming and going this time of year. The area is not conditioned at this time.

5. Yes, I did pull out the paper end pieces. Actually complained to national gypsum about two issues (being a newbee, what do I know). The cardboard end piece that facilitates pulling the edge paper off, often was missing or off center requiring cutting the double panels loose with a knife and further having to trim the loose paper. The other complaint was the non-existant “GridmarX” that were supposed to be there, but were lacking.

6. The engineer in me has a really dumb question. Any reason, not to space the rock 1/8” or on all sides so that mud is forced between the sheets to help bond the edges? …other than the obvious on-center alignment issue where applicable.

7. While I can’t say how much mud behind the tape is “enough”, I did a good bit of trial and error with my knife and the homax 6500 taper. Both to insure mud squeezed out 100% of edges when imbedded, and also pressed even harder to insure even more was left behind, then of coursed removed that tape and started over. Every so often poked with finger too, looking for a slight indention in the tape.

8. Mud was thinned to a pourable yet reasonable cake batter texture for taping. Just a tad thicker for boxing, not pourable, more like sour cream. Took these two “references” thickness from some on-line recommendations and seemed to work. Any thicker and the tape wouldn’t run though the taper, and broke when pulled. Likewise, the mud in the boxes any thicker and I couldn’t “force” it out for a smooth finish, especially on wall vertical seam going up from floor.

9. I was pretty careful with centering the tape, worst issues were in the corners where rolling sometimes took it left or right.

Again thanks for the insights.


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## Magic (Feb 20, 2014)

Did you prefill? 
Knock on wood I have never had a job crack all to hell but i wouldve prefilled that whole ceiling with durabond before ever taping. I believe prepping to tape is one of the most important part of our job to get it right. Not saying thats your problem. You must have movement but at least the movement would have been reduced with a good prefill. I wouldve prefilled walls with an eighth inch gap too.


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