Paint problem - spider cracks (ceiling, sand, color, photos)

[Pine to Vine]

We recently had our new condo painted (flat paint over eggshell - both water-based). In several spots, spider cracking has appeared. While it shows up in different places, it is mostly concentrated where the wallboard meets the concrete celling. On one wall, interestingly enough, the cracking surrounds every electrical outlet, door frame, vent, door stopper, etc. Our painter has tried two fixes on test areas - 1) compounding, sanding and re-painting and 2) putting on a semi-gloss coat to fill the cracks and re-painting with flat. In each instance, the thin spier-cracks returned. Someone theorized the concrete ceiling might be wicking in moisture, but that doesn't explain the areas around the electrical outlets and vents, etc. He suggested that an oil-based primer might do the trick in all areas.

Anybody have any ideas what might be happening? More importantly, anyone have ideas for a possible solution?

Thanks for your advice!

[kodaka]

It's not the paint, it's the substrate. After drywall is nailed to the studs, the joints and cuts and nails are mudded and taped and sanded, before being primed and painted. The mud is a cement-like mixture that then dries. Temperature, humidity, and air pressure changes can cause it to expand or contract. The drywall underneath the mud is also subject to the same pressures, but being a different material, it will expand and contract at a different rate. The different rates of expansion/contraction puts tension on the mud and the only way to alleviate that tension is to form a crack. The difference between the rate of expansion/contraction for drywall and concrete is significant, which is why you notice more cracking there.

If you put twenty or thirty coats of paint on the wall, eventually you'll have a thick enough coat that the cracks occur underneath and do not come all the way to the surface where they are visible. Another option would be to remove all the drywall mud and put in something else. And then the final option would be to address the temperature/humidity/air pressure changes going on in your condo.

[Pine to Vine]

Originally Posted by kodaka

It's not the paint, it's the substrate. After drywall is nailed to the studs, the joints and cuts and nails are mudded and taped and sanded, before being primed and painted. The mud is a cement-like mixture that then dries. Temperature, humidity, and air pressure changes can cause it to expand or contract. The drywall underneath the mud is also subject to the same pressures, but being a different material, it will expand and contract at a different rate. The different rates of expansion/contraction puts tension on the mud and the only way to alleviate that tension is to form a crack. The difference between the rate of expansion/contraction for drywall and concrete is significant, which is why you notice more cracking there.

If you put twenty or thirty coats of paint on the wall, eventually you'll have a thick enough coat that the cracks occur underneath and do not come all the way to the surface where they are visible. Another option would be to remove all the drywall mud and put in something else. And then the final option would be to address the temperature/humidity/air pressure changes going on in your condo.

Thanks - this is very informative. What should I replace the mud with? Also, would a sealer that would lock the moisture in the drywall in help?

[JimRom]

I'm not sure that humidity is the issue here. These cracks could also be caused by settling of the construction, especially if they are running out at the corners of windows, doors, and boxes. How wide are the cracks, and how far do they extend? A picture of the worst offenders would be helpful for us to tell what the underlying cause might be.

[Pine to Vine]

Originally Posted by JimRom

I'm not sure that humidity is the issue here. These cracks could also be caused by settling of the construction, especially if they are running out at the corners of windows, doors, and boxes. How wide are the cracks, and how far do they extend? A picture of the worst offenders would be helpful for us to tell what the underlying cause might be.

Sorry but can't get a good picture. The cracks are hairline like a spiderweb and don't resemble the larger settling cracks I'm familiar with in our old home. The closest I can come to is this picture, if you can imagine no large cracks and no flacking at all (the upper left hand corner of the image most resembles the cracking):

All sizes | Albino jumping spider | Flickr - Photo Sharing! (http://www.flickr.com/photos/21837606@N00/3493408563/sizes/z/in/photostream/ - broken link)

The building paint contractors (not the one I used) came by today to look at them. They have painted over 60 units in the building and this is the first time they have seen this in any unit. While they are as perplexed as me, they agree it is not the paint, as most of the walls looks great. In one corner, they are going to test applying an oil-based primer, skim coat and sand, then re-paint with flat. We'll leave that for a week and see what happens.

There is no guarantee this will work, but it sounds worth a try. In the meantime, I welcome any insights or ideas from anyone else with either similar experience or a theory as to what might be at play and how to fix it.

[Pine to Vine]

So it appears even the oil based primer isn't covering all the cracks. Is it possible (and a good idea?) to simply sand down the painted walls, put a fresh coat of primer on them and start again?

This is the best photo I can get: http://i1129.photobucket.com/albums/m514/johnmurphy02/P6150017.jpg (broken link)

it looks better after the primer but there are still cracks and I'm not certain what it will look like after applying the paint.

[chet everett]

You picture is not sharp enough for me to tell but it looks an awful lot like a moisture related issue.
If this was due to "settliing" or something related to the different rates of expansion and contraction it would NOT happen as QUICKLY as it appears in your unit NOR would it be happening as badly IN THE MIDDLE OF WALL unless there is an active geologic fault running through your unit!



I would check but the "relative humidity" and compare that to other units AS WELL AS using a CALIBRATED electronic probe to measure moisture inside the drywall.

There are many different kinds of "drywall compound" (or 'mud') some of which are essentially identical to automtotive body filler (Bondo). Though such compound is EXTREMELEY water resistant and stable I would recommend against using in UNTIL THE WORK IS UNDER TAKEN to find the root cause of what appears to be a MOISTURE ISSUE -- if you do not solve that issue the walls themselves can continue to deteriorate into a sorry state and eventually you will have more mold than a cheese cave!!!

[Pine to Vine]

^^^ Sorry, wish I could get a better picture. Logic tells me moisture would be the culprit. So why not go with logic? I haven't ruled it out, but the fact is this is high-rise building, and no other units have experienced this problem - above, below or to the side of us. The cracking is more pronounced towards the corner and ceiling seems and in areas where there would be no source of water, such as where an interior bedroom wall meets the ceiling. This makes me wonder if it isn't that the sheetrock wasn't properly seemed and sealed well in this unit - hence my thought to sand and start from scratch.

I am not a construction person, so I am not dismissing your suspicion of moisture - just trying to solve a mystery. Fortunately, the management of the building is committed to making this right.

Thanks for your ideas and suggestions.

[Pine to Vine]

Update - problem resolved.

One painter we brought in had a theory that our original painter had not allowed the first coat to sufficiently dry before applying the second coat. This caused the first coat to pull awayas the 2nd was applied. Further supporting this theory is that the cracking occurred almost exclusively where the paint was cut-in (thus heavier) vs rolled.

This may or may not be true. Regardless, the important thing is that we identified and implemented a fix. It goes as follows:

> Oil-based primer
> Clear coat sealer
> Skim coat and sand
> Latex primer
> Paint

Yes, a hassle, but all done.