I removed the wallpaper from plaster and lath walls. I found a few cracks that were easily repaired but previous owners did a terrible job with patching. I would like t o get rid of imperfections and make it smooth looking. Can I use the pre-mixed USG (green lid) all purpose joint compound to do this? Do I need to use a bonding such as plastic weld first? If not what should I use? I don't want to deal with structo lite which from what I read seems hard to work with.
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3 Answers
I would patch cracks with general purpose , any large cracks use paper tape or mesh so it won’t crack in the same place after being painting. To give a really easy nice finish after the patch work is done is to use “topping mud”, it is much lighter than general purpose and way easy to sand. I used this method on “quick skim” jobs where I wanted to change the texture type, you can use general purpose for skim but it takes longer to dry and is a bit tougher to sand. (Topping mud is not hot mud it is lighter and softer than general purpose and not for cracks).
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I've seen "light weight" joint compound in my local big box store, but nothing called "topping mud", at least as I can recall. Are they the same product?– SteveShCommented Mar 5, 2020 at 13:07
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Light weight and topping may be regional terms and probably are the same. I just checked on a web sight and they called it topping compound with the same description (thiner and easy to sand) “pros love it because it is easy to work with” (from family handyman how to choose Joint compound).– Ed BealCommented Mar 5, 2020 at 15:16
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1Lightweight and topping are not the same in California. It's worth the trouble to go to a specialty drywall supplier to get honest to goodness topping mud. (You'll probably end up with a box/bag combo, which is a pain to manage because on your second opening of the bag, you'll have chips of dried crap messing up the rest of it. Decant the whole bag into a big bucket straight away.) Commented Mar 5, 2020 at 17:04
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2And if you use mesh tape to cover cracks, use a setting compound, not all purpose. usg.com/content/dam/USG_Marketing_Communications/united_states/… Commented Mar 5, 2020 at 17:06
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Setting mud or hot mud is much stronger but also tougher to sand. I agree the best results on cracks are from setting or hot mud + I usually don’t recommend for newer DIY after telling a friend that tried to ruin a nice 8” mud knife and tray, and they were mine, LOL. He mixed an entire tray full of 30 minute did not mix very well and had a horrid mess, it cost him a couple o cases but we got it fixed up. Use just a little mix well and use sparingly for best results.– Ed BealCommented Mar 5, 2020 at 19:30
I've seen it flake off a ceiling, use a veneer plaster instead.
While I have used Structo-Lite for many years without issue - if your repairs aren't of substantial depth/thickness, any discussion here would be moot.
For cracks and what not, on plaster walls, 90 Minute Setting-Type should suffice.
Just mix what you need and store the bag in a dry place. You'll more than double the coverage area, and won't have to worry about contamination, freezing, or disposing of a half empty bucket of bad mud later on.
