Diagonal Drywall Cracks

[boisefrank]

What do you think causes most diagonal cracks around doors and windows?
I have my suspects and found lots of speculation on the web but cannot find any proof as to the root cause of such cracks.

Also, what is the best way to repair such cracks?

[Mike Gill]

Re: Diagonal Drywall Cracks

The diagonal craks are obvious signs of some downward movement. Check the door - it will also show a problem. Occurs on load bearing walls. Most often it's from a footing settling(sinking). A good snow load acting down on the wall can also cause the movement. Happens often in the rooms above garages where the lolly column footings sink a bit from the load.

[SteveH]

Re: Diagonal Drywall Cracks

Read all about it: http://www.umass.edu/bmatwt/publicat...shrinkage.html

[BMOPE1]

Re: Diagonal Drywall Cracks

Investigate for differential settlement structural issues. Presuming the header and wall are properly sized and constructed, the most common cause is differential shrinkage of the header relative to studs. Lumber shrinks minimally along it length and much more so across width and depth.

[Myron Ferguson]

Re: Diagonal Drywall Cracks

After the structural problem is corrected you will have to V-groove out the cracks. It is better to do this because the crack is not a surface crack. Prefil the groove with a setting compound. I like to use a paper tape for this type of crack because paper tape is stronger than most mesh tapes. Your finish coats can be regular joint compound.

[boisefrank]

Re: Diagonal Drywall Cracks

I have dealt w/ several issues related to such cracks. I have found several sources on the net, including the info from UMASS that SteveH posted. Most of the time these cracks occur within the first year of the home being built.

For some reason the I-joists always get the blame! I belive it is a shrinkage differential between the dimesional lumber header and jack studs.

I have seen some suggestions to not nail the drywall to the header, just the jack studs and top plate. That allows for slight movement of the header. Not sure I buy that. Anyone tried that?

[betterdrywall]

Re: Diagonal Drywall Cracks

bosiefrank : i have to agree with you , was talking about this probelm today on a job we did back during deer season , none of the other homes we did that month have had this probelm , so i know it is not because of bad joint compound or taping , even though it is just minor mud cracks still something is causing it to move , everywhere there is a stess points inside the home there is a crack . if the jack studs have any gaps at all i was told they needed to be shimed or replaced or they would cause monvement , also i have repair several of these cracks with usg 90 minute and they came back . still having a time tring to explain to the builder that it is not because of the quality of the finish work . i really think there is something going on with the roof load . maybe not enough stiffbacks . there is cracks in the floor and the builder had the concrete work done when there was alot of rain , also it is sitting ontop if red select clay . even though most of it is minor , the 3 or 4 areas that are bad i'm sure will come back , and i dont even see a solution to the probelm . he really needed to set the house up about 2 ft higher, using packed sand or something that wouldnt move as much , its been sitting all this time in a hole with water running toward the house . today he hired a dozer guy to put the property to grade . i just dont understand myself , kinda at a loss here with this project . sad thing is this is the first home i have done for the guy . its like i told him today i'm not going to make excusses , if the work my crew did is bad , i will do what ever it takes to correct it . but so far , since the 90 minute cracked back out , i really think this is on the builder.

[Kgphoto]

Re: Diagonal Drywall Cracks

Drywall doesn't hold the house together, the lumber does. So if there are recurring cracks, it isn't the drywall and taping.

[Bsmoothe]

Re: Diagonal Drywall Cracks

not sure if this helps betterdrywall but we just did a house up here and same circumstance 1st job for new builder. no permanent heat he kept torpedo heater hooked up to thermostat. problem was it ran out of kero every night he wouldn't get there till midday, we told him its gonna cause some cracking big temp change 60 with during day 25 at night without sure enough it cracked, not diagonal however yours seems structure related but have seen garages crack diagonal when heated by propane heater and someone comes in after we leave and shuts house door.man does that sucker get hot! when we pull open door in A.M. you feel the heat blow past you. feels like enough heat to create my own t-storm. siding starts cracklin too . we got diagonal cracks that day. above doors next to beam.

[Myron Ferguson]

Re: Diagonal Drywall Cracks

Poor heat and high humidity are major causes of drywall cracks. Heat, humidity and airflow need to be at the right level Before-Durring-and After 24 hours a day for a quality drywall job. I know a lot of drywall contractors supply their own heat, but does this take care of the Before and After? I only supply my own heat for some smaller jobs and then it is often turned off at night because a contactor who doesn't understand the rules. This happened to me recently, the only hamn that was done was that i missed a days work because he compound was still wet. But a days work is a days pay, so it was a bigger deal than the contractor really really understood. I think drywall cracks are seldom if ever my fault unless a seam is placed in a poor location like right along the edge of a door header.
I try to avoid seams that land along a header and I also try to avoid fasteners in the wide dimension of lumber because they usually pop.

[not-the-inspector]

Re: Diagonal Drywall Cracks

I try to avoid seams that land along a header and I also try to avoid fasteners in the wide dimension of lumber because they usually pop.

seams of drywall at the tops of windows/doors are the main problem. seen it a million times and a half.