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Question DetailsAsked on 11/23/2014

What caused my 4 month old condo drywall ceiling to crack?

I moved into an 8th floor condo in Chicago. The building was built in 2003 and my unit had concrete ceilings. Before I moved in, I hired a contractor off Angie's List to install drywall as the concrete ceiling was visually unappealing.

The contractor first installed metal tracks into the concrete ceiling and then attached the drywall. Four months have passed and now hairline cracks are appearing between the drywall joints. Before I contact the contractor, I'd like to know the cause of the cracks. Many posts on here are for ceilings with an attic above; not a concrete ceiling.

Any help identifying the potential causes and recommended fix is greatly appreciated!

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Voted Best Answer

I have to admit that I have never seen drywall (as opposed to suspended acoustic or decorative ceiling panels) hung from metal tracks - presumably Unistrut ? I guess if a light-weight closed-face track were used you could run sheet metal screws into it to secure the drywall, but usually wood firring strips would be used for this - trimmed to thickness to provide a planar surface then fastened to the concrete with expansion anchors or Tapcon screws, then the drywall screwed to them with drywall screws, at 16 inch on centers typically even though code allows 24" on centers.

As for why your ceiling is cracking - while I suppose it is possible the concrete floor above is sagging, that is unlikely - and could be easily check for by standing up with your eye level near the ceiling and looking across it. If it is sagging down fairly smooth in a bowl shape (in one or both directions) then one of two likely causes - the metal tracks were not properly secured (which would probably make for uneven sagging across the surface), or the concrete is deflecting. A concrete floor, if designed/built properly, should not noticeably deflect after construction.

If instead the sagging is due to the individual sheets sagging down between the tracks or channels, so you have a washboard or wavy appearance to the ceiling, then the tracks were not put close enough together (if waves or sags are parallel to the tracks) or drywall screws were too far apart along the tracks (if waves or sags run crossways to the tracks. There are specific fastener spacings for each thichness/type of drywall. Lets assume they used 24 inch track spacing rather than 16 inch spacing or 24 inch grid like a truly experienced pro would, so the fastener spacing in the perpendicular direction to the tracks obviously has to match the track spacing or they will totally miss, but in the other direction and down the edges along the tracks the specified spacing would be much closer together to provide the required support. So, if they used say 24" spacing both ways, they would be WAYYY short of the necessary number of fasteners (for instance, US Gypsum 1/2" drywall requires 12" spacing with screws, or 7 inch double-nailed), and the entire ceiling could be coming down gradually as the fasteners pull through the drywall. Failure to use the correct type of screws (Bugle shaped are recommended for ceilings), or using regular drywall rather than ceiling-rated drywall (which is stronger and lighter than comparable regular drywall) or using 24" spacing with lighter drywall could also cause this. For instance, since this was only for appearance he might have used 1/4 (against recommendation for single-layer) or 3/8 drywall, where for a real planar, uniform ceiling surface over large areas (bigger than bathroom ceiling) you want to use 1/2 inch - though that is generally NOT REQUIRED BY CODE under a concrete ceiling. Only way to assess these factors is checking the drywall thickness at a hole (maybe ceiling light fixture opening), and using a stud/metal finder to determine the fastener spacing.

Here is a link to the most common residential code in use, showing required nail ande screw spacing for ceiling drywall of various thicknesses -

One other possibility that came to mind - is it possible the cracks ARE at a joint - perhaps end joints between sheets that did not have a track under them so are unsupported across the width ofthe ends except at the tracks, so are sagging down and cracking through the joint paper ?

If I were checking this out, the first thing I would do is climb a ladder and press strongly upward on the drywall in several places with my back to see if it is coming loose - i.e. it has vertical slack in it. If it is, it would freely move up a fraction of an inch till it hit the tracks, probably popping out some of the joint compound filling the screw holes in the process. I won't advise you to do that, because if it is coming down and about ready to let loose, you could end up on the floor with a lot of drywall on top of you.

One other possibility is that the airspace above the drywall was not ventilated, so the drywall is taking up moisture and sagging as it loses strength. That air space should have had airgaps between the tracks (unless side perforated) and code-required plenum air ventilation grills, and depending on specific code for your area, perhaps forced-air ventilation as well.

Probably the best thing to do is drill a few small inspection holes in the drywall (typically 1/2") near the worst crack areas, and look up in there with an illuminated color video inspection camera - about $40 or less a day rental typically at home improvement box store or tool rental place or some auto parts stores, or less than $100 to purchase at Amazon or Harbor Freight. You would be looking for gaps between the drywall and the tracks indicating the screws are coming out of the tracks or that the screws are pulling through the drywall in which case there might be large ragged drywall and paper "blisters" or loose popouts bulged up out of the top side of the drywall by the screws (more than just the little bulge-out from the screew coming through), or gaps between the concrete and the tracks indication the whole assembly including tracks is pulling free. The latter would be tougher to determine, because it is possible they might have not run all the fasteners up tight as a means of levelling out the face of the tracks to provide a planar surface.

Unfortunately, you need a real experienced installer or engineer to determine what the issue is, and whether it needs to come down or if just more screws into the tracks will take care of it - and finding someone with the experience and the eye to figure it out will be tough. I guess all you can do is contact the contractor at this point, AFTER taking a bunch or pictures (and eMail them to yourself and maybe to your work eMail with original saved on the eMail server so there is a dated record of them on you ISP's server), and see what he says. At most he will probably say just minor shrinkage cracking (though that should not happen in drywall that hasnot gotten wet) and butter over the cracks with drywall compound and repaint - which will make them go away for now, but does not cure the cause.

Answered 5 years ago by LCD

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