February 21, 2014

The Complete How-to for Fixing Sheetrock Joint Cracks

Hello friends and fellow DIY-ers. Have you ever walked into a room and noticed a crack above a window or door, or below a window? If you live in a house over twenty years old, you've probably seen them, especially if you live in an area where there is a lot of ground movement. Houses settle, we all know that, and with settling comes cracks, usually in the joint where two pieces of sheetrock meet.  Once you've ruled out or repaired foundation damage, this post is about how to fix the cracks when you finally decide it's time to do something about them.

This post is picture heavy, so I am going to place a page break here so it won't freeze slow-loading computers. Right click to open in another window or tab if your computer does load slowly and let it load while you look at something else.

Please excuse the picture quality in this post. I had to take off the window covering so every daytime photo is with the camera pointed at the light, a photography no-no, but that's the way it is with windows. Every night photo is just as bad because there is only one light in the room right now.

Several years ago we had a professional fix several cracks over windows and doors. They didn't look great and within six months, they had all cracked again.  Before putting in our new wood floors, we had someone examine the foundation to see if anything was shifting. No, he said, nothing more than normal settling. Fix the cracks, install your floors, and go on, he said. Before having anyone else come fix the cracks, I did a lot of research online, and consulted a forum where painting professionals hang out. 

What I learned:
  • Windows and doors are basically a square hole, creating a weak spot in the solid plane of the wall.
  • Sheetrock should not have joints at corners of windows and doors, but should wrap the corners, meeting in the middle of the window.
  • But many sheetrock installers put joints in the corners because it is easier and uses up sheetrock scraps.
  • Paper tape is stronger than mesh tape.
  • Setting type joint compound (aka hot mud) is stronger than all purpose drywall compound (aka mud) and should be used on all joints.
  • But all purpose joint compound is less expensive, comes pre-mixed, is workable for a longer period of time, and because it can be used for all applications it is easier for the installer.
  • When repairing cracks, the original mud and tape should be removed, both insuring good bond to the sheetrock, and lessening the thickness over the crack.
  • But most contractors don't remove anything, they just tape over what is there.
  • Contractors who hang out at professional forums and tell you the right way to do things are impossible to find in the local phone book or Angie's list!

After interviewing six contractors from the above sources, none of whom would remove all of the tape and mud that is currently on the joints, I decided the only way to get this done right was to do it myself.  It wasn't super easy, but easier than I thought it would be, and my walls look great. Plus, it saved me several hundred dollars. (I had several cracks.)  And, when I was fixing the cracks myself, I found that every one of those previous repairs was done using mesh tape on top of the old cracked mud and tape.  No wonder they didn't hold.

Complete list of tools and materials needed:
Painter's plastic and tarp (if you need to protect existing floor)
Eye protection
Utility knife and blades
Setting type joint compound
All purpose drywall compound (if you need to add texture)
Roll of paper tape
2-3 inch putty knife
10-12 inch drywall taping blade
Drywall mud pan
Pole sander and sandpaper
Texture sprayer

Here's what you need to remove the existing tape:
Utility knife with new blade (trust me, you want it sharp).

Before you start, put on eye protection and set out some eye wash or drops just in case anything gets past them. Also, wrap a bandaid or tape around the knuckle of your middle finger on the hand you use with the knife. You won't appreciate this tip unless you don't do it.

To protect your flooring, put painter's plastic on the floor and pull the edge up so you can tape it to the baseboard.  Then put a tarp on top of that.  If you just use a tarp, dust and debris will sift down between the wall and the edge of the tarp.  Been there, done that.

Step 1. At the joint, make perpendicular cuts just above and below the crack and deep enough to cut through the mud and tape. That will keep from tearing the tape further than you want to repair. I made my cut along the crown molding at top and about an inch above the window so I wouldn't cut into the corner tape. You might have metal corner bead there. You should have metal corner bead there. But that was another shortcut taken by Moe, Larry, and Curly at my house. I have paper tape on outside corners.
Hold the knife at an angle and cut a line about two inches on either side of the outside of the tape. The tape is two inches wide and I've found that the mud is applied just over six inches wide. If you see that your knife is cutting through sheetrock instead of mud, move your cutting line in.  It's ok if you don't have a straight line; it might even be better.

Step 2. You are going to remove the mud between the two cuts. I have found it easier to remove the paint layer first and then the mud. Still holding the knife at an angle, score the area between the cuts. Then slide the knife blade under the paint and peel it off. If you have a problem, rub a wet cloth over the cuts, wait a minute and the paint will pull off the mud easier.

Step 3. Now that the paint is off, the mud is easy to remove by scoring at a shallow angle.  It shatters off as you scrape, which is why you wear eye protection and have the eye wash.  It goes everywhere.
Again, if you have a problem, rub a wet cloth over it, wait for it to absorb, and then continue to scrape with your blade.  When the mud is wet, it's easier to scrape with the knife held perpendicularly.  As you can see, the mud isn't very thick, about 1/8 inch thick.  You don't have to remove every bit of mud there, just get as close to the sheetrock as you can.  Then you won't have a big hump when you re-mud the joint.

Step 4. When you have most of the mud removed and you can see the tape, rub a wet cloth across the tape and let it absorb a minute. Then you can put your knife blade under the tape and slide it around all the edges to break the seal from the remaining mud.

Step 5. It off in one piece and the sheetrock under it should be pretty clean. If there is any mud left there, it will wipe off easily with your wet cloth.

Step 6. If there aren't any, or enough, nails or screws holding the edges of the sheetrock to the 2x4 behind it, now is time to add them. That will help keep your joint from recracking in a few years. On one joint I repaired, there was no stud behind the joint at all. No wonder it cracked.
On this joint, did you notice the way the crack went up, then across the tape and then up again? I was a little worried about that, but when I got the tape off, I see the reason. A sheetrock nail was hammered in so hard that it cracked the sheetrock and made a small bulge in the sheetrock. The only fix I could do was to shave off the bulge. There wasn't another place to put a sheetrock screw as there wasn't a 2x4 above the header. I peeled the corner tape down to see how far the crack went and luckily it stopped just under that tape. You normally don't have to touch the corner tape/bead. If you are only doing one crack, go on to the next step. If you have multiple cracks, repeat the above steps on all of them before going on.

Now you are ready to re-tape the joint. For this you need setting type joint compound, also called hot mud, which only comes in powder form, a narrow blade (2-3 inch) putty knife, something to stir and mix with (I use a 1 inch putty knife), a drywall mud pan, and of course a roll of paper tape.

Step 7. The directions on the bag are for mixing a large quantity. You don't need that much. It's basically a 2 part powder to 1 part water recipe. If you are only doing one crack about the size of the one I've shown, you can use 1/2 cup powder and have plenty. This stuff will harden even if you wrap it in plastic, so don't mix a lot more than you need. Since this is a small amount, you can easily mix it in the mud pan. It should be the consistency of frosting, the kind you spread with a knife. Add more powder or water as needed to get it right.

Step 8. With the 2-3 inch blade, spread a thin layer of mud along the joint. Work it into the crack and any nail holes and make sure it's wider than your tape. If your windows are like mine, they have a lot of nail holes (some of them really big) near the corners where you and previous owners have installed curtain rods.

Step 9. Cut a length of tape a bit longer than you need, wet it, and butt one cut end against the cut edge of the original tape. In my joint, I put the cut edge against the crown molding. Hold that edge with your fingers and pull the 2-3 inch blade down its length firmly, pressing it into the mud base.

Step 10. Put another coat of mud over the tape, making sure the edges are covered so the tape is sealed. If an air pocket gets under the tape, the tape could come off, or crack and you'll have to do it all over again. Let that dry. It may need overnight.  This is where I also taped my extra nail crack and folded the corner tape back over.

Step 11. After the joint is dry, knock off the ridges with a piece of sandpaper or putty knife. Then mix another batch of hot mud in your mud pan. Distribute it evenly along the width of the pan so you can scoop out an even amount along the width of your 10-12 inch drywall taping knife.

Step 12. Starting at the top, spread the mud down the width of the joint. It should fill the area you cut out. You will probably have to put more on your blade than I've shown, or load your blade again. Smooth it with one long stroke if you can. If you have crown on top and window trim on the bottom, you'll have to take a stroke from each end which will leave a lap mark in the middle. Don't worry about it, you can smooth it with sandpaper after it's dry. You can see in my photo that I've got some ridges across the top even after I smoothed it several times. It kept catching on an uneven place. They'll sand off. Let this dry completely.

You can use just the sandpaper, but using a pole sander (aka idiot stick) is better because it sands flat and even.

Step 13. Lucky 13 because you are almost done. Unlucky 13 because you get to find out why it's called an idiot stick. Place 100 grit pole sander paper on the swiveling sanding block if it isn't on there already. Plop the sanding block against the joint and sand it smooth. I'm short and have to stand on the step stool to get enough pressure on it. Now put your palm flat on the wall and rub it back and forth (not too fast) across the filled area. If you can feel any humps, sand that spot again. If you feel any dips, or if you feel the lines on either side of the filled area which is very common because of shrinkage, you need another thin layer of mud. That's what I felt here.   Now run your fingers through your hair.  Gross, huh?

Step 14. (optional) You can use all purpose mud for this layer if you want. This time I applied the mud over a wider area. After I applied the mud, I ran my taping knife from side to side, applying more pressure on the sides than in the middle to create a tapered edge. If you drag a crumb across the surface on your last sweep and it looks perfect except that scratch, don't worry about it. The more you work on it, the worse it will look. Let it dry and the scratch is easy to fill.  If your walls are smooth, paint and you are done.  If your walls are textured, go on to the next step.

Sometimes bubbles pop up as you smooth the mud. Sometimes working it back and forth will smooth them over, but most of the time, they just pop up again. Once it's dry, sand off the bubbles and fill the holes.

Step 15. When it is dry, sand again and you are ready to texture. There are a lot of texture spraying products on the market, but the one I like for small areas is the Homax Touch up Sprayer. You can buy them or order them through Home Depot too. I like this one because it doesn't clog up like the spray cans and the texture is smoother. I also have an electric sprayer but won't use it in a room where I'm trying to protect the floor.  This little Homax doesn't have a wide spray pattern so it's perfect for tight spots and rooms with carpet or furniture. The down side to that is that you have to hold it closer to the wall and pump it. You can see that the new model comes in a streamlined package where mine came in a box.

Step 16. All purpose mud is better for this part, although as little as you use here, you can use the hot mud and get it finished before it's too hard to work.  Hot mud is NOT easy to clean out of the Homax reservoir.  Whether you use all purpose or hot mud, thin a cup of it to the consistency of pancake batter. That's a couple of tablespoons for a cup of all purpose. It's probably more than you need, but I have found that his Homax sprayer works best when it's full. For this, mix your mud in a cup until it is smooth. Don't try to put it in the reservoir and shake it to mix. Been there, done that too. Pour the mud into the reservoir over the tarp, screw the pump on and turn it reservoir up immediately because it drips in several places.

Step 17. Look at the texture on your walls, and set the dial on your sprayer to the right size.  My walls are knockdown with a pretty big blob pattern, so I set it on the largest setting.  Pump hard to get large blobs.  Cover the area you have new mud and spray randomly farther out so it feathers out. It looks like it isn't covered well, but each spot of texture will be larger when it is flattened. It's easy enough to add more later too. Let it set up for a few minutes. Good time to rinse off the sprayer. It's easier to clean the reservoir after it's soaked awhile.

Step 18. Starting at the top, hold the 10-12 inch drywall taping knife at an angle and pull it lightly over the texture, but don't flatten completely. Sorry, I couldn't hold the camera and the blade at the same time.  While the texture is still wet, wipe off any splatters that went down the wall, on the window, or other areas.  If it's too close to the texture you want, like on the crown molding, leave it until after you've painted and wash it off.  The paint will keep the texture on the wall from washing off.

This is the same Step 18 from a different angle to show the thickness. Let dry completely. If your walls have just one or two coats of paint, you are now ready to paint and you are done. If your walls are like mine, and have four or more coats of paint, the edges of the new texture are too crisp. After the texture is completely dry, rub a wet cloth or sponge lightly over the texture and it will soften the edges so they match better. Then let dry again, it won't take long this time, and paint.

That's it. You're done. I just have two last tips, and these concern cleaning your tools. Empty the leftover mud into the trash, not down the drain.  When using hot mud, don't clean your tools in the sink; the mud will set up in your pipes. When cleaning the Homax reservoir, you can pull the plug out of the bottom and use a brush or cloth to clean inside. I can stick my pinky finger in that hole and bend it enough to clean out those corners.

I am linking to:
Frugal Friday at The Shabby Nest #95
Be Inspired at Common Ground #33
The Charm of Home #20
Thrifty Things Friday at The Thrifty Groove #7


  1. Wow! Living in a 100+ year old converted barn there are cracks all over the place! Love all the photos you gave us... and the great instructions!
    Hugs from your new blogging sister,
    Beth P

  2. Great tutorial. Want to come and repair a few of my cracks?

  3. Hope you'll post pictures of the finished project, you should brag a little after so much work.

    1. Thanks! I thought I would post some before and afters when I finish painting. I didn't back off and show the whole wall though. There were 4 cracks around this window.

  4. Great tutorial! Thanks for linking to TTF this week.

  5. That's a great article. I don't have cracks in the walls, but my walls keep cracking along the ceiling. I know the house is settling, and I'm pretty sure previous owners just kept covering up those separations. When I'm ready to move out, I'll do something with it, and until then, it isn't causing a problem, and they don't seem to get bigger or spread. This will be helpful for me for another kind of damage in the bathroom, though!

  6. Thanks for sharing, it was interesting to read!


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