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.

Discolored Plaster

water stained plaster
Discolored Water Stained 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 without 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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61 thoughts on “How To: Diagnose Common Plaster Problems”

  1. The plaster wall around my ac vent has began to crumble and created a pile of plaster dust on the floor. It is in the corner of the room, partially obstructed by a crib. What would be cause? Major problem?

  2. The plaster ceiling in my 1949 home sustained water damage from a roof leak — discoloration, bulging, flaking, falling, etc. I’d say the area was about 3 square feet. We put on a new roof and fixed the ceiling — scraped, mudded, painted. That was a year and half ago. I just noticed that it’s starting to bulge and flake again in the same area (though no discoloration). Does this mean we didn’t fix the original problem??

  3. After about 3 roof leaks over 2 years, my horsehair ceiling has cracking paint, but no water stains that I can see. How does horsehair react to water damage? Could the cracking paint be related to the water leak? Thanks!

    1. I would guess the the cracking paint is due to the water leaks but the plaster can stand up to the abuse a little better. Just make sure the leak has stopped and the plaster is still well adhered to the lath.

  4. Have found on my newly acquired 1923 Foursquare that when the asbestos containing Vermiculite attic insulation was removed (done properly) that *both* the plaster and lath has pulled away from the joists (spaced 24”). Seems like the small nails used to secure the lath could not hold over time. I am trying to avoid the mess and the work of dropping the ceilings. It seems the best approach may be to set up temporary walls to push the plaster lath back up and the reattach using something like narrow crown staples for each lath at each joist? Seems like a lot of work and the full dimension 2×4 joists should probably be reinforced. I suspect that the joists aren’t stiff enough and that people and things stored in the attic may have caused them to flex this allowing the nails to work loose due to time and gravity. Also, the Vermiculite particles could become wedged in the gaps.

    Looking for suggestions.

  5. I keep finding plaster pieces on my rug and table seems like it must be falling from the ceiling but I’ve never seen it happen and there doesn’t seem to be any damage on the ceiling. I can’t figure out how this is happening! It’s a high ceiling with a wooden beam across the top. The ceiling was painted a year ago.

  6. Hi
    Wallpaper has cracked open about six inches and plaster has expanded and appears to have crystallised into something which looks like shards of fibreglass. Any ideas of the cause and solution?

  7. I am getting lots of powdery dust from the plaster on my wall. As I was cleaning it up I got a taste of salt from the dust. This has happened before but It is getting worse. What can be causing this?

    1. Plaster is flat , no cracks in the area but 100 yr old wall paper is bubbling at a few seams and trying to pull away.No dampness or water around… why??

  8. Our horse hair walls have a mark on them that keeps reoccurring. Like bleeding through the wall. I can send a picture

  9. I have a buldging area, but it is hard as a rock. Can’t push it back in at all. This is about hip height, and at the top of the wall where it meets ceiling there are what look like settling cracks in this corner area.

  10. Hi,
    it is a relief to have found your site. I’ve bought a new build by the sea. I’ve come to inspect it, and on a few interior walls the emulsion paint about 12 inches from the bottom of the wall has bubbled out and when lightly touched by hand turns to dust. I don’t think it is rising damp because they are all interior walls with an open garage below.
    They repainted it, and it has started to happen again. Inside one wardrobe, the paint was actually wet it is taking a long time to dry out.
    A friend has suggested water pipes behind the wall maybe leaking? What are your thoughts.

  11. house is 60 years old
    ceiling are great
    hole house was plastered and done very well!
    walls have a oilcloth cover or something
    and getting hairline spider cracks on the seems
    what is the best fix
    thx ron

  12. Hi
    My name is Angela and we have wet plaster damage def getting it tested and fixed but I have to ask we have this lighter brown thing that is in the crease where the ceiling and wall meet that looks like latex and it just starts growing and gets big a couple have fallen on the floor looks like latex but it breaks when it falls kind of like how a mushroom grows but faster I do have a pic if u need to see it . I really hope u know what it is It’s creeping me out lol

  13. Hi I have a question along 1 exterior wall my plaster is cracking where the ceiling and wall meet. A few little chunks have fallen out . is this a sign of a serious problem and how do I fix it.

  14. My 1940s Georgian has a hump in the ceiling plaster from end to end in our living room (about 25′). It’s about 6″ wide and very thin, just a shadow really. The other day the paint developed a hairline crack along small sections of the hump. We moved in less than a year ago, and assume the previous owners just attempted to skim coat and paint a crack before selling. Any ideas?

    1. I had this problem on several walls, in fact was watching it grow over a period of several months, and I later found a 15 ft length cast iron drain line in the crawl space was split along the bottom dumping all water from the kitchen under the house. After I fixed the plumbing and then the walls the condition has not recurred.

  15. My home was built in 1890. We had a leak in the upstairs bathroom. The room below the plaster has pulled away from the wall the gap is about 3″ now. It runs along the door jam. Would I follow the same steps as you showed in the video or will I need to replace that wall.?

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