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Plaster looks "cracked"


derek's Avatar
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12-05-06, 12:54 PM   #1  
Plaster looks "cracked"

My home, built in 1960 has plaster walls that look horrible. The walls have the look of a cracked eggshell. You can't really feel the cracks, but you can see them at the right angle. No amount of painting will hide the cracked appearance. I'm guessing the original plaster contractor was a butcher. Any ideas?

 
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marksr's Avatar
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12-05-06, 02:16 PM   #2  
They may be settlement cracks. What I usually do is etch/scratch them out with the edge of a putty knife [screwdriver will work] and fill the cracks with durabond. Spackling will also work but may not last as long. Paint seldom covers cracks.


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12-05-06, 03:14 PM   #3  
How large are the areas enclosed by the cracks?
Like does a crack surround an area the size of the palm of your hand or larger? Or, do you cover a multitude of cracks with the palm of yur hand?
Is this real plaster over gypsum lath with full thickness plaster?
Can you scrape off the finish?
How much of a room or a wall or the house is effected?
How many times has the wall or room or house been painted?
Has there ever been wallpaper on the walls?
Is the ceiling effected?
What else do you know about the history of the house? What was the reputation of the contrator? The plasterer?
The lather?
Did the house ever go through a winter without heat?







I think I know what happened.

 
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12-05-06, 04:58 PM   #4  
tightcoat - can you tell us what happened?

i have a similar problem except my cracks are more pronounced and i can actually peel the paint away from the cracks. my house was built in the 20's but is new to me, has plaster walls, i can't tell how many times they have been painted, the house definitely is a little more moist than typical houses and I want to repaint everything.

any suggestions on what to do before repainting?

 
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12-06-06, 02:00 PM   #5  
puher, It sounds like someone who knows paint better than I can help you more.

I wait for more information from derek before I render my opinion on his guess.

 
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12-06-06, 03:21 PM   #6  
Crazing (networks of fine cracks) of plaster is often a result of using a mix with a high cement content or a sand that contains too much dust. These fine cracks can usually be covered by a quality paint. If cracks are larger, that is often referred to a map cracking. Cracks are deeper and wider and are often a result of a high cement mix or plaster drying too quickly. When too much water evaporates from plaster in the first few hours this is usually referred to as plastic shrinkage cracking. If cracks occur after plaster sets up, these are called drying shrinkage cracks. Plaster applied in too thick layers will also crack this way. Cracks can be filled, primed, and painted. For plaster walls, you can use plaster paste, mixed from powder or premixed. Putty knife can be used to fill small cracks. After it dries, sand, prime, and paint. For drywall, joint compound or spackle can be used.

Some cracks may need to be cut out with utility knife to make them larger and dust brushed out with old paint brush and filled with patching material. Wide cracks may require patching tape (drywall mesh or joint tape). Cut tape a few inches longer than the crack so it will extend beyond in both directions. You can then fill crack with patching material and putty knife, using strokes perpendicular to the crack, apply the tape making sure it is smooth and then apply patching material over the tape.

 
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12-06-06, 05:31 PM   #7  
Posted By: puher i have a similar problem except my cracks are more pronounced and i can actually peel the paint away from the cracks.
Sometimes with many old coats of paint you will have an alligatoring effect. It usually doesn't peel. Sanding and maybe filling is the usual fix.

As old as your house is, the walls were most likely painted with oil base paint when new. There is a good chance that lead based paint was used For new paint to adhere properly all the loose paint will need to be removed. If the surface underneath the loose paint is glossy it will need to be coated with a solvent based primer [or sanded] A thin coat of joint compound should fill any remaining irregularities.

Because of the chance of lead, due caution should be used to contain any dust or chips - ESPECIALLY IF ANY CHILDREN HAVE ACCESS to the the area being worked on.


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12-07-06, 09:11 AM   #8  
I've been on the road, sorry for the late response.

The cracking is large in scale, but not noticible unless you look closely at the wall at an angle. "Crazing" would be an apt term for it. Definitely not settlement cracks. Pretty much every wall has them, but I have no intention of fixing them by chiseling as you can see them but really not feel them. I'm certain it's a plaster issue that was from somebody who did something wrong.

I found a specialty paint called Scrubtough that hides them pretty good, although it's expensive, it seems to wear like iron.

 
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12-07-06, 02:00 PM   #9  
What you describe is probably environmental. Maybe there was a thrmal shock sometime during the life of the wall. A more likely thing is that the plaster dried too fast either from air movement or excessive heat. The owner or general contractor probably did not provide adequate heat or heated the house too quickly. I once ran into some plaster that was like you describe. It was cracked into postage stamp sized pieces. The plaster was well bonded and could not be removed from the substrate nor the finish scraped off the brown. It was as smooth as glass and so hard that if one struck a putty knife or margin trowel down it all that would happen was a black mark. I suppose the plaster was in the nieghborhood of 40-50 years old. It is now going on 75 years old and as good as it was then. Don't complain about the plasterer. Be glad you have plaster rather than some inferior product like drywall.
You have the solution already, youfound a good paint. Unless you can take the finish off of the brown coat you have nothing to worry about. If the finish can come off then take it off and refinish.
The problem is in the finish not the brown coat.

Has the house ever gone through a winter unheated?
Is this frame construction?
Is the plaster over gypsum lath?
Are the walls straight?
Are the angles straight and sharp?
Are the corners straight and clean?
Are the ceiling effected?
Are the ceilings textured?
What part of the country do you live in?

 
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