Cracks on Sheetrock joint compound

Question

There is a round hole in my ceiling wall which i want to fix. I covered the hole with steetrock as best as i could, put a meshed tape around the border and then applied sheetrock joint compound.

But the next day i see lot of cracks on the joint compound (attached picture )

Any idea what i am doing wrong ? Thanks in advance.

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Answer 1

The joint compound you used was either not mixed properly or had already dried out to some extent before you applied it. It also looks like you exacerbated this by putting on a really thick coat. (also I see the edges and I don't see tape nor joint compound... you mud the edges of your sheet first not the middle)

I personally would try to scrape as much of that off as possible. Immediately. If you leave it you will either:

1. Sand the crap out of it, chunks might come off, and if everything goes as well as possible you still have huge divots/lines. You will then need to add a few (much thinner coats).

2. Just add more joint compound and push them into cracks. They won't perfectly fill cracks and then after you sand for a long time it still won't be smooth.

What you should do...

• scrape it off
• only add joint compound to the area below mesh tape and a couple inches to each side
• your joint compound should be consistency of a runny peanut butter (if you eat Nutella, like a new jar... not the crusty Nutella in an old jar).
• after two layers around the tape you can try to add small, smooth layers to center... probably two more to get it right. You can't just slop on the stuff in the whole area unless you are very skilled and are using a very loose/runny mix.

Answer 2

How old was the joint compound you used? This looks old. You also applied it way to thick. You need to do many thin coats and let each coat dry completely between coats. Joint compounds don't usually shrink and crack if they're new and applied right.

Answer 3

The only time I seen drywall mud shrink like that is when it is put on too thick. It shrinks as a rule, and when it is that thick, the shrinkage has to show somewhere. If it is set in thin layers the shrinkage occurs in its thickness. When it is applied too thick, say maybe 1/4" or thicker, then the shrinkage occurs in both thickness and in its width.

You can add more in thin layers that will fill the cracking, but it will shrink into those cracks too, so more will be needed to get them filled in enough to level everything out.

When adding drywall mud, if the surface is essentially filled flat with the adjacent surfaces, resist the tendency to add more mud than needed to fill the cracks. A few tight skim coats may do just what you need. Then sand smooth.