What's the REAL purpose of paper tape on drywall?

Question

I've seen many arguments use this tape use this joint-compound do this do that.

So from what I can tell with my very limited experience it would appear that tape just helps prolong the life of what is an acceptable look for drywall.

All drywall mud will crack and shrink in time by having the tape over it you hide the first area to degrade which would be the joints and corners thus prolonging the life of the look.

Beyond that it may help with paint and such however I am unsure of how true any of this is to be honest.

I have seen joints last for at least 6 years without tape on an exterior wall so that is worth noting. I have seen joints with mesh and paper tape mesh tape seems to want to peel away if you do not use hot set mud first don't know why but over time this has just been my experience.

I guess when it boils down to it how many years does a decent drywall job last whats the life expectancy is it 10 years 20 years more?

Other than hiding the crack that will likely form behind the tape I see no purpose for drywall tape over joint compound the latex paint used will likely seal things up fairly well I would assume after the coat of primer I would almost imagine for the most part a guy could get away without using tape for quite some time. Plus I would imagine as soon as the joint starts to fail behind the tape it will put a decent amount of probability that the tape will also start to separate not long after this causing you to have to refinish the drywall at a minimum in the problem areas which would be easier to patch and sand then to have to apply tape to and patch and sand as well...

So it does make me wonder is it really that much more beneficial to use tape on seems as one would maybe gain a couple of years at best of lifespan vs having no tape at all...?

Answer 1

All drywall mud will crack and shrink in time by having the tape over it

You put the mud over the tape, not the other way around!

You're right: tape is unnecessary for things that are under 1/16th" or so. But larger voids really need tape.

The butt joints in long-side drywall edges are a special case. Drywall long-edges are tapered, so that you can have a smooth finish after the thickness of tape and mud is added. So the tape helps in building up the thickness of the joint, making less mud (and less sanding!) to have a flat surface at the seams.

Despite the comment regarding "hot mud," I like the fibreglass mesh for covering largish voids of 1/8th or more. It lets the first coat of mud through, which then gets a second coat after the first dries. I have successfully covered 3/4" voids this way. (Not recommended, but possible!)

When using mesh tape with water-based mud, don't put it on too thick where there are voids, rather, build up multiple thin layers.

Whenever I wonder, "This seems silly or unnecessary" about a common practice, I consider that time is money, and it would not be a common practice if it didn't pay off in some way! I imagine the results of mudding without tape would probably get the contractor called back for a re-do quite often.