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Is it true that fill up the joints before taping can prevent cracking?

Mike Liu
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It can be true depending on a few things. I would use a 20 min setting compound to fill all gaps/cracks/damaged areas. It will set by the time a room is done. Follow up with a tape and longer setting compound. For a DIY 20 min compound also acts as a warm up.

anm767
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    20 is really fast (especially for a taping novice). I don't recommend anything quicker than 45, which is still plenty fast for a same-afternoon overcoat. – isherwood May 12 '21 at 12:45
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Your first mudding step is taping. In this step you fill cracks and holes that require taping in the same step as applying the tape over it, and more mud over the tape. This is all one step with the same batch of mud.

In this first step you are also filling the joints.

I believe the real question is:

Should you intentionally leave a gap, to be filled when taping? Or should you butt the panels tightly, thus requiring you to only tape over the join?

A filled and taped gap provides better mechanical stability, than a tight join between panels that is only taped.

If there is a gap, the mud can penetrate deeper into the join and adhere better to the joining panels where it provides more strength at the joint. The adhesion as well as the hard fill prevent the kinking and sheering that causes cracks.

In contrast, if it is a tight fit, no mud can penetrate the gap, and the only mechanical bond is at the taped surface. This cannot be as strong as when there is a bond over and within the join.

So when there is a gap, make sure it is filled, and then tape over it. You don't have to let the mud in the gap harden first before taping; you can do it all in one step.

You can use mesh tape to bridge gaps and holes that are more than peraps 1/4in wide. If the hole or crack is too large, the mud you apply will not hold and fall through unless you use a mesh.

Do not plan to first fill and then later tape over hardened or dried drywall.

Screws and minor indents that do not require taping are mudded independently, which is why perhaps you might have heard that they could be done first. However, usually they are covered with a different finishing compound that is used for all the mud work in a later step.

P2000
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  • Not true. If you fill large gaps with mud and then tape right over the mud will shrink and putt the tape into the joint making it weak. You should prefill wider joints and let them set if using a setting compound or let them dry if using an all purpose. Then tape over. – redlude97 Apr 12 '21 at 07:24
  • @redlude97 shrinkage of setting compound is not much and it is not going to make the joint weak. I wouldn't use drying compound for this first step. He can do gap filling and taping in one step, using setting compound. The important point is to let some setting compound into the gap for a better bond and better stability. That (and good framing) prevents cracks. – P2000 Apr 12 '21 at 16:06
  • Filling and taping is probably best fit a setting/hot mud with a setting agent that dries faster and shrinks less than air dry.... I am not a pro, check this – KCD Nov 27 '23 at 03:10