Joint compound question
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Tuned
Joined: May 2003
Posts: 317
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From: New Jersey
Joint compound question
This is more of a Home Improvement question, but If I substitute the word "Garage or Shop" for basement I can maybe sneak it in. I taped and applied 2 coats of mud to my drywall seems and thought I had sanded enough to apply paint, Paint is dry, seems now stick out like sore thumbs. Do I have to sand paint 1st or can I try and do another coat of mud over the painted seems?
Thanks, Chet
Thanks, Chet
Post Fiend
Joined: Jun 2002
Posts: 13,873
Likes: 3
From: Atlanta GA
Did you leave a small gap between the drywall and push the tape into the seam a bit, then mud it. When you sanded it, did you use a flat block on a pole and feather in the edges slightly? Did you give it at least one coat of primer just on the seam area, then primed the wall again, then paint?
Elder User
Joined: Jun 2004
Posts: 540
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From: Northern MD
You can sand the joints with 80 grit paper, but you've got to be careful not to sand through the mud into the tape or sand into the paper facing of the sheetrock. More than likely, you probably didn't tape the joints correctly. It's a 3 step process, tape, block, and skim. The tape is applied with a 4" knife. The block coat is applied with a 6" or 8" knife. The block coat is only supposed to fill in the tapered seam, no more. Finally, you skim each side of the joint with a 10" or 12" knife. This tapers the seam out into the sheet and minimizes the "hump" effect. If you've done it correctly, there should be little sanding required. Butt joints are done the same way, but require more care because there is no factory taper. If you treat applying mud like bondo (apply on what you need, no more), you can't go wrong. I was a finisher for 8 years before and during college, and worked piece-work and hourly for a living. It's hard, messy work but just like bodywork, if it's done poorly everyone can see it.
Senior User
Joined: Mar 2004
Posts: 111
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From: Klamath Falls
You can apply a skim coat over the paint using a 10" or 12" wide knife. Instead of sanding with 80 or 100 grit paper, try using a wet sponge. At the home warehouse stores you can find heavy sponges about the size of a large brick. 'Wet sanding' is done after the compound has dried. You moisten the compound and, working with the sponge and a 6" knife, smooth and feather the joints. PVA primer is recommended as a first coat. If you are not going to texture the surfaces, try using a stipple roller to disguise the joints.
Postmaster
Joined: Aug 2004
Posts: 4,004
Likes: 1
From: North of Boston MA
I have also had good luck with a wet sponge but in a different way. Since the finished joints are usually smoother than the surrounding sheetrock, they show up pretty well, especially once painted.
What I do is take the wet sponge (on dry joints) and dab at the joint compound. Try to make it so the texture of the compound matches the plain sheetrock. You have to start with a good quality joint to begin with though.
Don't be afraid to cut out a bad spot or a bad joint and do it over again. It beats looking at a lousy joint forever. It takes practice to get them right.
I recommend PVA primer as well but be warned - once it goeson it makes the joint compound hard as rock and next to impossible to sand.
What I do is take the wet sponge (on dry joints) and dab at the joint compound. Try to make it so the texture of the compound matches the plain sheetrock. You have to start with a good quality joint to begin with though.
Don't be afraid to cut out a bad spot or a bad joint and do it over again. It beats looking at a lousy joint forever. It takes practice to get them right.
I recommend PVA primer as well but be warned - once it goeson it makes the joint compound hard as rock and next to impossible to sand.
Freshman User
Joined: Aug 2003
Posts: 33
Likes: 0
Try floating in the opposite direction than you did your first two coats. This will fill in low spots that will "shadow" when painted. I use this technique especially for repair work where there is no recess for the tape. To be honest, taping is a skill that takes years to master. first coat-tape with 6"knife. Second coat=float with curved trowel to cover tape. Third coat =feather out on both sides with straight trowel. Sand, then prime. You will see your mistakes then. Float again with straight trowel, if necessary. Prime and paint. Hope this helps. 
