Repairing Old Cracked Plaster Walls

Old starter homes are always usually a project in itself. With plaster walls, there are a few tricks and methods to repair small and large cracks in walls and ceilings. I had an uncle who was a master plasterer. I, of course, learned a lot from him in 1976 when I bought my first starter home built in 1935. Here are some pointers for your repair project.


* Drop cloth, goggles, dust mask (Gloves are optional)
* Step ladder for ceilings or high wall repair
* Plaster or patching material
* Hawk or piece of scrap plywood cut in a square for mixing plaster
* Spackling knife, size of your choice, or a rubber kitchen spatula (for small cracks)
* Razor knife or an old can opener (one that punctures the top of the can in a Vee)
* Sash brush or paint brush (optional substitute, spray water bottle)
* Shellac
* Staple gun and wide straight-slot screwdriver (optional for type of repair)
* Sanding block and 60 or 80 grit sandpaper
* Vacuum

• Use a drop cloth for big and small projects to protect the rug or floor. There are different varieties of materials you can purchase. For small cracks, you can use a joint compound because it is easy to use, easy to sand, and it dries fast. The small stress cracks don’t need to be extensively prepared. Just use your spatula or putty knife, fill in the crack, dry, and sand flush. The joint mixture shrinks a little so you might have to repeat the process. When everything is dry, you can sand it flush with the wall (See Paragraph 6 below for finishing the repair).

• For larger cracks, decide which tool size to use to prepare the crack. You start the prep work with a can opener by placing it in the top of the crack and pulling it down to the end. This will create a ‘V-shape’ opening. This will give the plaster something to adhere to on the wall. If the crack is larger than that, use the razor knife to cut the ‘V’. While preparing the crack, remember to use a mask and goggles to keep the dust away from your eyes and lungs.

• For large cracks, choose a compound you think will do the best job. Ask someone in the hardware store for advice if you are not sure. You can use spackling compound from a can. It dries fast with little shrinkage, but it is harder to sand. Another type is patching plaster. This stuff dries fast in a couple of hours; it doesn’t shrink, but is definitely harder to sand. Personally I would rather sand. I hate to do things over unless I have to. Besides, don’t they make a palm sander for boring jobs? I’m for that!

• After you have chosen your compound and prepared the crack, you clean out the crevice with a vacuum or a brush. Mix up some of the plaster compound in small amounts because the mixture dries within 30 minutes. Spray water or use a brush and a container of water (I like a sash brush), and wet the crevice.

• Get your hawk or plywood for the plaster. Use your trowel, putty knife, taping knife, or whatever you are using, for mixing. Read and follow the manufacturer’s instructions on mixing proportions. When thoroughly mixed, apply the plaster to the wall from the top and work your way to the bottom. Try to keep it as smooth as possible so your sanding won’t be as difficult. I take a sash brush, with a little water, and smear the plaster to reduce the excess. You shouldn’t press hard or you’ll remove plaster from the crack. Make sure the plaster is at least flush with the wall or a little more. Let dry.

• After the patchwork dries, sand it down with 60 or 80 grit sand paper. You can use a palm sander if you have one. When finished, vacuum all the dust (did you remember to put on your goggles and mask?) and put a coat of yellow or white shellac over the repaired crack. Let dry. This will seal the crack and helps the plaster bond to the wall.

• Your repair job is finished. You can now paint or wallpaper your wall.

• If your crack is large and very long like in a ceiling area, it may be from the house still settling or ground shifting. If you follow the previous instructions, you should be fine. However, sometimes the same area may crack slightly again at some point in the distant future. When you fix it the next time, the crack should be smaller. Repairing it will be less troublesome and it should hold for the duration of your ownership. The ceiling crack I repaired spanned the entire length of my dining room. My repair job held for ten (10) years while I was living there.

• The last step involves a repair of a large dent, about the size of your fist. You can actually see a depression in the wall. The best way to repair that is to get your staple gun and the large screwdriver. Put the flat blade of the driver in any part of the indentation and then straddle the tip with the staple gun. Shoot a staple and remove the screwdriver. You will see that the staple is not flush into the wall and it is somewhat raised. Do this a number of times within the depression. The staples give the plaster something to grip. Follow the previous instructions for the repair.

• You are now ready…to clean up of course, before your wife gets on you for leaving a mess.


Go out and buy your wife a new set of rubber spatulas. She’ll be happy because you will be taking her old ones. Sometimes you may want to use the spatula instead of a putty knife because it is so flexible. It is great for small crack repairs.


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