You will undoubtedly encounter countless companies advertising "plaster repair." In a sense, this is true, they will repair your plaster walls after a fashion, and what they use is commonly referred to "plaster." What they mean is almost always what is known as joint compound, and I myself sometimes refer casually to this material as "plaster."
Both traditional plasters and joint compounds are applied using similar and even the same tools. Joint compound adheres to a surface by the use of adhesives in the compounds, traditional plasters form a mechanical bond.
The primary difference is that traditional plasters are much harder and when combined with lath and studs enhance structural stability. Traditional plaster offers a solidity, in effect, a roundabout way of getting to a kind of stone.
Joint compound, by contrast is cosmetic, it's meant to cover up the seams between wallboards and hold tape in place. If you've been inside certain North Loop and other newer condos, you'll notice don't even bother taping the seams, it's a 'look' and structural integrity isn't compromised in any way.
Essentially, drywall is a paper and gypsum (plus additives) skin over studs because people don't tend to like living like Leo Johnson in Twin Peaks. The structural strength of drywall is actually in the paper-- quite ingenious, really-- once you tear or cut the paper, it breaks easily.
Except when thorough action is immediately taken, drywall that gets wet is finished, more for the landfill (according to The University of California Santa Cruz Department of Environmental Ethics, up to 75% of all drywall ever produced is in a landfill).
Traditional basecoat plaster, by contrast, because it always contains a proportion of dried but not cured material, is able to use part of that water and the rest tends to pass through to the surface (this is why you see 'efflorescence' (a kind of chalky, bubbly stuff) on the surface of traditional plasters that have gotten wet and/or notice the white "putty coat" is soft and separating from the basecoat).
Apart from durability, true plaster offers vastly superior sound dampening qualities to drywall. Ever notice how 'quiet' old houses feel? There's never been a good game of Ghosts in the Graveyard/Sardines played in a drywall kitted house.
From an environmental perspective, traditional gypsum plaster is carbon neutral, and lime plasters are actually carbon negative (as in the lime plasters remove more CO2 in curing than was used to produce them). Although it is being addressed (somewhat), drywall (remember all that in the landfills) releases sulfur dioxide as it decomposes, in addition to a number of other nasty things to drink and breathe.
Most of my bids are at the very least competitive with drywall companies, and seldom involve much demolition. The application of traditional plasters is a skill, drywall/joint compound, because they can be sanded (oh and can they!) are less so. If the immediate financial costs are commensurate (saying nothing of the environmental costs), there's a good bit of money going somewhere else with drywall, and it's not to the workers.
email: chris@uptownplaster.com