How To: Diagnose Common Plaster Problems

By Scott Sidler April 18, 2016

How To Diagnose Common Plaster ProblemsAfter a century or so plaster walls and ceilings can develop a variety of problems from neglect or abuse. Your plaster can tell you a ton about issues that may be developing around your house if you know how to listen to what it is saying.

In this post I’ll show you how to diagnose the most common plaster problems and what they mean. Plaster is often like the canary in the coal mine. If there is a problem brewing it will likely show up first in the plaster. So knowing how to diagnose plaster problems will help you solve little problems before they become big ones.


Cracked Plaster

This is probably the most common problem people notice with their old plaster walls. The good news is that cracks in your plaster don’t necessarily mean trouble. Sometimes they are a warning sign but other times they’re just like wrinkles on our faces that appear with age. How do you know the difference?

hairine cracks
Hairline Cracks
  1. Hairline Cracks – These cracks are small enough that you can barely fit a fingernail in them. It doesn’t matter which way they are running either, vertical, horizontal, or diagonal these are the most benign of all the cracks and unless they are growing or you really can’t stand the sight of them there is no reason to mess with them.
  2. delaminating cracks
    Delaminating Cracks

    Delaminating Cracks – These cracks are a sign of plaster pulling away from the lath behind it. These show up on both ceilings and walls, but can be the most dangerous on ceilings. When plaster begins to pull away from the lath there is a chance it may fall away from the wall or ceiling and come crashing down. The cracks often run parallel to the lath (horizontally on walls and lengthwise on ceilings). You may see multiple cracks or bulges running parallel on the ceiling like in the picture which is a sure sign of plaster pulling away from the lath. You can use the video tutorial to learn how to reattach the plaster and prevent further damage.

  3. settlement cracks
    Settlement Cracks
    Photo Credit: //

    Settlement Cracks – If a part of the house is sagging you may find converging cracks running across your plaster walls. Yes, you’ll want to patch and fill these cracks, but address the bigger issue of foundation problems first. A group of cracks converging in one direction are often signs of settling. If you see this kind of crack call a professional, especially if they are new and growing.

water stained plaster
Discolored Water Stained Plaster

Discolored Plaster

This is the early signs of water damage to plaster. Brown water stains will begin to show up soon after a leak begins. The easy way to solve them is with a stain blocking primer, but that won’t do anything to resolve the water issue. You need to find the leak and seal it up before things get worse. Don’t delay.


Bubbling Plaster

bubbling plaster
Bubbling Plaster

Once the water damage becomes severe then the plaster will begin bubbling and bulging. You may reach this stage without any noticeable water stains, but when this happens a portion of the plaster will have to be removed and patched. Use the steps in my post How To: Patch Plaster to repair the damaged sections.

If not repaired soon the damage will just continue and you run the risk of developing mold in the affected area. Water and plaster are not a good combination so find the source of the leak first and do everything you can to stop the water.


Bulging Plaster

Plaster is a pretty incredible material. I have seen a plaster wall come completely loose of the lath and bulge out about 4 inches from the wall with falling or even cracking! It’s not just cracks that mean plaster has come loose of its lath. Just like delaminating cracks bulging plaster looks exactly the same except this time there aren’t cracks in the surface.

If you see bulges in your wall or ceiling and the plaster can be pushed back up against the wall then it’s time to reattach that section of plaster. Use the steps in my post How To: Repair Plaster Walls to get things stabilized again.


Remember, plaster is the canary in the coal mine and these are just some of the most common plaster problems. It will start showing you leaks and settling before anything else so look for the signs and fix the issues before they demand your attention in a more expensive way.

If you have any plaster issues not mentioned here leave a comment below and I’ll try to answer as many as I can about how to resolve the issue. Good luck and watch that plaster!


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10 thoughts on “How To: Diagnose Common Plaster Problems”

  1. Hi Scott.
    We just had a mold issue taken care of in the attic of our 1969 townhouse. Also, we had the old insulation removed, and will be reinsulating. Yesterday we noticed three small bubbles, in a straight line in the bedroom ceiling plaster which is directly under the attic. One has cracked. And then another appeared in a different area which wasn’t so much a bubble, but just like a pushed out piece of plaster about the size of a quarter. We were able to simply push that back in. From your article (thanks!) I’m leaning towards water damage. Does that make sense? Does that happen in such a straight line? The water/mold company is coming back to reinsulate, but I assume the bubbling should be addressed first, yes? Thank you again for the article.

  2. Do you think encapsulating crawlspace and installing dehumidifier and pump would help dehumidify home? We have a 100 year old large home across the street from the Bay in Tampa. We have ground water intrusion and after heavy rains, water pools under home (mainly under front porch area), but house gets humid. We use dehumidifiers which helps. We have balloon frame home (three story) . We are worried it will cause structural damage. We have regraded land, installed drains, gutters, etc (used an engineer and spent thousands over the years.). Crawlspace people are advocating closing vents but we are afraid that will just trap the ground water underneath the vapor barrier. Any opinions on encapsulating, to use or not to use vapor barriers, vented vs. unvented crawlspaces? Our home is wood and in very good shape. no warped floors, etc. We are installing a whole house dehumidifier inside. There is tremendous controversy on this and we do not know who to believe.

  3. I wish I could post a picture of what my ceiling is doing! It literally looks like a checkerboard of squares that are all cracking and sagging and looks like it will start falling any minute! Our landlord “assured” us it isn’t an issue that needs him to repair it, but it’s an older home probably built before the 60s! I’m just worried that my ceiling will start crumbling all over my furniture or someone will get whacked in the head! Is there anyone I can send a picture to that can tell me if I need to worry??

  4. Hi. I have a tenant with issues who constantly stomps her feet extremely hard on the second floor. Now the walls upstairs cracked and buckled in 2 spots and my ceiling, well the top of my wall right under the ceiling is cracked. Could constant stomping cause plaster to crack like this?

  5. Hi, I just noticed a huge patch of bubbled plaster in the wall of an interior closet. About a foot long and 6-7 inches wide, it’s dry and crumbles to the touch. My clothes hang in that closet; will mold get into my clothes? The building is old and my landlord never does repairs. I can’t repair it myself or he will have a fit. It doesn’t rain much here (southern California) so if I put up a plastic shield of some sort will that protect my clothes? If I keep the lightbulb in the closet on and the door open will that discourage it spreading? Is it harmful to be near (my bed is next to closet)? I only noticed that one patch; I’m afraid to check for more! Thank you.

    1. Dot, continued water intrusion almost always results in mold. The only solution is to have the source of the leak patched as soon as possible. In the meantime using some damp rid in the closet will help keep the humidity down but your landlord needs to step up and fix this quickly.

  6. I’ve seen plaster used a lot in my neighborhood, but I wasn’t aware that there were so many things that could require fixing. From what I’ve seen, like you said, plaster is an amazing material. It’s good to know that it will show issues first so that you can get them fixed! Thank you for taking the time to walk through a couple of the more common issues.

  7. Hi again, before I read this article I wrote you about a problem with very shallow surface damage in a bedroom in my brick veneer house. However, I am not certain there is lath on that wall (east side of house). On the west side, there is definitely a bedroom & stairwell that are plaster over lath, but in another west-side room (laundry room), the plaster appears to have been laid directly on masonry – no lath visible, but plaster has fallen off leaving a crumbling concrete-like surface both above and below grade. How can that be fixed?

    (I am going to fix the west-side bedroom that does have lath using the Wally’s Magic product). Thank you so much, and I’m very glad to have found your blog.

    1. Susan, Big Wally’s can be used on plaster on masonry walls as well you just don’t have the ability to utilize the anchors. I have found that’d plowing their repair steps and finding an alternate way to keep the loose plaster pressed firmly against the wall for 24-36 hrs will result in a lasting repair. You may have to get creative to find a method that will apply the right amount of pressure against the wall for that time though. Usually plywood on the wall with angled 2×4’s installed as temporary braces will work. It’s not as pretty but it gets the job done!

  8. Scott, I am interested in fixing all the hairline cracks in my plaster ceiling. They seem to be along all the edges of the 4×4 plasterboard sheets under the plaster. What is the best method for fixing these. Do I tape them, use plaster washers, or some other method? Any help would be appreciated.

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