Drywall seam 'speed bump'

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Old 07-24-17, 07:58 PM
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Drywall seam 'speed bump'

So awhile back I had to replace a 4'x8' section of drywall. No problems in the corner or ceiling but where the new piece meets the old piece I have an ever so slight 'speed bump' on the seam.

Fortunately it's only 4' long since the lower half of the new piece is hidden by the fireplace surround.

This is not the first time I hung drywall but first time I had this particular problem.

Odd thing is, the raised seam didn't show up until I applied the color coat of paint. It's as if the moisture in the latex paint caused the seam to raise. No problem with the primer.

I think I will try to carefully remove some joint compound to level the seam, and re-mud with something other than joint compound. Shrink free spackle?

Once I am happy with the repair I will use a 4 inch roller and repaint the seam. If the joint doesn't rise again and the paint matches ok I'm good to go, if I need to repaint the whole wall, no big deal.

Thoughts?
 
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Old 07-24-17, 08:49 PM
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You either didn't feather it out far enough or put too much on and didn't sand it flat. The answer is a wider knife and more joint compound. Add more j/c on both sides of your "bump". Sand, prime, and paint.

No, you don't use spackle!
 
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Old 07-24-17, 09:05 PM
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"Add more j/c on both sides of your "bump". Sand, prime, and paint."

That's plan B.

I'm far from a pro at this but have done enough and am half decent at it. Was feathered out enough and was sanded very nice. As I said, the bump appeared only after applying the color.

OK, I won't use spackle but why not if it's just over the 1/8" seam?

Thanks for your info.
 
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Old 07-24-17, 09:10 PM
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The bump was there before you painted, it did not magically appear because of the paint. It appeared after you painted because you probably don't have an eye for what you are looking for before the wall has any sheen on it. If you take a wide knife and put it perpendicular to the wall and use it like a straightedge, you will probably be able to see the bump more clearly. Having a bright light to shine across the wall also helps you see better.
 
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Old 07-24-17, 10:01 PM
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Could be I guess. I used a bright light to shine across the wall while working but maybe missed it. I know paint makes defects show up very clear!
 
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Old 07-25-17, 03:53 AM
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I agree, it was there prior to primer/paint. A bright light viewed from an angle usually brings it to your attention. Also paying attention to the wall while the primer is still wet will highlight any defects in the hanging or finishing.
 
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Old 07-25-17, 05:01 AM
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i had a crack between backer board and drywall, Was worried about the same thing. What I did was to use my electric wood plane and went about 2 inches on each side 1/8 inch deep. Put oil based primer on than used 60 minute mud on tape, After just finished wall normally. no bumps which I was worried about.
 
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Old 07-25-17, 09:40 AM
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Odd thing is, the raised seam didn't show up until I applied the color coat of paint
Not a surprise to me. Contrary to intuition, paint often makes imperfections more visible rather than hiding them. X steered you right on the fix.
 
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Old 07-26-17, 08:09 PM
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Also paying attention to the wall while the primer is still wet will highlight any defects in the hanging or finishing.
Good tip, hopefully I remember that next time.

I figured I have nothing to lose so I decide to dig into the 'speed bump' so I used a utility knife to slightly score about 1/8" away on each side. The latex paint peeled off and I found very powdery JC. Removed it and hollowed out the ridge a bit. Filled with new JC, primed and painted using a 4" roller. Paint matches perfect and the speed bump is gone!

paint often makes imperfections more visible rather than hiding them
Especially if it has any sheen. Probably why the builder of our spec house used flat for the walls. It's amazing how good a joint can look until you apply a satin paint!
 
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Old 07-27-17, 04:47 AM
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Ya, the higher the sheen the more defects will show. That is the main reason to eyeball the wall while wet with primer. Wet primer [or paint] always has a good sheen so paying attention while it's wet will point out any discrepancies in the wall. More times than I can count I've seen something in the wet primer and then had trouble finding it after the primer dried.
 
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