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Taped joints - Mud shrinking?


doruho's Avatar
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08-28-08, 11:49 PM   #1  
Taped joints - Mud shrinking?

Hello,
Finishing my basement. I've taped and mudded the drywall (ceiling too). Thought it was smooth and flat, but after priming I found out how off I was. Many of my seems seem to form a depression. There is a tangible, visible channel 3 or 4 inches wide. Most of them maybe a 16th of an inch deep, a couple even deeper. I've tried to do another skim coat over these joints (sometimes twice) but after the mud dries, there is often still a depression.

I used mesh tape on these joints. I used pre-mixed lightweight joint compound. To try to fill these depressions, I've been using a pre-mixed skim coat compound. I'm using a ten-inch knife, trying to press hard on the outside edges and more lightly down the middle.

Is the mud shrinking that much? Using the mesh tape, I would have expected the seems to be higher if anything.

How can I level off these seems? Do I just need to keep going over them with more layers of mud? Would it help if I used a non-shrink setting compound instead, or would that be too hard to sand?

Thank you in advance for any suggestions.

 
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marksr's Avatar
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08-29-08, 05:49 AM   #2  
OK let me try again, my first reply disappeared

I think you might be pressing too hard on your knife and removing too much compound. Are you using a sanding pole or block when you sand?


retired painter/contractor avid DIYer

 
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08-29-08, 06:09 AM   #3  
I use a pole with 100-grit paper (That's the finest grit they had at my local Ace). I try to keep the head at an angle and try to sand as lightly as I can.

Maybe I *am* scraping too hard. I've been running the knife down either side, pressing harder on the outside edges. That tends to leave a bit of a ridge down the center. I've been concerned that that ridge might be hard to sand down, so I then run the knife (lightly) down the center to try to smooth it out.

Should I not worry about that ridge, and sanding will take care of it?

Thanks.

 
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08-29-08, 03:34 PM   #4  
If you are using ready mix joint compound - it's easy to sand
Personally I'd rather apply an extra coat of mud than do any extra sanding but since what you have done so far hasn't produced the desired results, I'd try things a little different. If you have the time, I'd just float 1 joint a little heavy, sand when dry and see if that fixes the problem.


retired painter/contractor avid DIYer

 
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08-29-08, 04:16 PM   #5  
Marksr,

That idea makes so much sense that I would have never thought of it.

That's what I'll do. One way or the other, I'll get there.

Thank you for your help.

 
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08-29-08, 04:25 PM   #6  
You do know that joints commonly take at least 3 coats, right? I get the impression from your comments that you might be thinking 2 coats is normal. You'll always have a depression if that's the case.

I usually tape... fill... then the 3rd coat I use a wider knife and go down each side of the center, perhaps leaving a small ridge in the center, which sands off. If after sanding, the light shows that some areas need a touch up, that's a final 4th skim coat. You can also check your joints by placing a wide knife end-on over the joint like a straightedge. It shouldn't have a valley in the middle.

But I don't claim to be the best finisher, or else I'd be using a box instead of a pan and knife! But some things are better not to be good at. LOL

 
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08-29-08, 06:14 PM   #7  
Oh yeah. I'm on the 3rd or 4th coat on many of these joints - That's why the consternation.

I had been leary of leaving a ridge down the middle, but my way hasn't been working, so I'll try it on one seam. If that does it, I'm golden.

BTW, this project contains 2,500 sq. ft of drywall (4 rooms, a bathroom, & a couple of closets, including all drywall ceilings). You can understand how anxious I am to be done with this part.<grin>

 
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