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How To: Diagnose Common Plaster Problems

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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78 thoughts on “How To: Diagnose Common Plaster Problems

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

  2. 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.

  3. 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.

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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.?

  9. My homes built in 1916 and there’s multiple problems I’m seeing bubbling walls bowing out and the top floor looks like the studs are coming threw the ceiling any info would be greatly appreciated as I have 2 children 2years old and younger can take pictures to upload if it will help

    1. Hi Joe,
      So sorry to hear you’re having issues, but love that you have such a historic home! Our best recommendation (especially considering you have children in the home) would be to use our directory to find a licensed preservationist in your area who can provide you an accurate suggestion upon seeing it.

      Best of luck to you!
      -Alyssa at The Craftsman Blog

  10. The wall in my kid’s room periodically has drips coming down. They don’t seem like water because they stay rather than evaporate. It looks more like old sweat. From what i can tell the wall is plaster with brick behind.

    We are in a rental in a 100+ year old Brooklyn, MY building. Our landlord has tried roof repair as we are on the top floor but has not changed the dripping.

    Thank you in advance!

    1. I had this exact issue in a rental in Chicago. It was from the old brickwork on the outside leaking into the walls and ceilings. The building probably needs the brickwork repaired. I found lots of mold on walls behind furniture. Hope you’re isnt as bad.

  11. I have an old home. I moved in January painted a month after and now 7 to 8 months later Im noticing cracks in 2 rooms. Some run horizontal on the wall and other are diagonal. I hung pictures about 6 to 7 months ago and heard some crumble sounds in the wall. It has been raining for about 6 months here and very humid. Im not sure if it is a problem or not? They recently appeared and were not there before. Thanks

  12. Hey Scott, we are working on my brother and sister-in-law’s new old house. They have painted the upstairs bedrooms already and now, a month later, the paint seems to be ‘running’ in waves, not drips, down the walls! It’s cold outside here, and the heat is off because they aren’t living in it yet. The walls feel clammy, for lack of a better word. Any thoughts? Would a leaking roof cause that, or too much moister in the cold air? I’m baffled. Thanks so much!

  13. My bungalow style house was built in 1930 and the upper floor may have been renovated in the 1950s or it may be original. It has plaster over gypsum board lath and at some point I think drywall mud skim coat. An exterior wall has the plaster pulling away from the gypsum board lath as though it never bonded to it? Any idea why the bond failed? Did someone skip a step? Did the more recent skim coat (circa 2000 I think) cause the failure?

  14. Hello Scott. I have a serious problem where the plaster has pulled away from the lath in two of my living spaces, the living room and dining room. It has fallen in the dining room. About 4ftx8ft has fallen. The living room has a large bulging cracked area and will probably fall anytime now. I want to know, why this is happening, and who do I call to repair my ceiling? I read one of the previous questions. Someone mentioned termites. Can that cause this? There is no water damage visible. Please help?

  15. The building was built in the early 70s. The plaster in my condo is cracking everywhere—kitchen, living-room, hall, bedrooms, bathroom. Both walls and stucco ceilings throughout.

    The same living-room wall has been repaired several times since I’ve been living here. Now the whole condo is cracking. Management Office says it’s the age of the plaster and most units have the same problem. Yet Management refuses to DO anything about it and says the unit owners are on our own re cost of repairs and who to do repairs.

    I can see where plaster has come away from the wall that there’s only cement wall behind a very thin layer of plaster, so the building was put up cheaply to begin with.

    How do I pay for and repair a 2-bedroom condo?

  16. We had a chimney leak that caused the plaster on the 2nd floor around the chimney to degrade. Once the damaged plaster was removed we got water damage on the first floor around the chimney. We thought we fixed the problem (both actually) and there is no moisture on the 2nd floor, but occasionally when it rains some of the degraded plaster on the first floor seems damp. Do you think there is another/more leakage somewhere or is it possible that the degraded plaster is reacting to the environmental humidity? There’s no rhyme/reason/repeated location to the first floor dampness. Happy to provide more information or pictures.

  17. Hi Scott, while replacing the flooring in one of our rooms, we found the very bottom of the plaster walls, behind the baseboards, had crumbled to pieces. No other issues with the plaster. This particular room sits over a crawl space, while the rest of the house is over a basement. How do we repair this, and do we have a bigger issued to address?

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