Why are ceilings painted with that rough, scratchy, bumpy, white paint, as opposed to the flat, smooth paint used on walls?
Helps to hide imperfections, and aids in sound deadening.
Keeps ceiling spiders from growing fat and lazy.
Because bumpy, scratchy surfaces discourage people from walking on them.
Aesthetics, sound deadening’, and because as NoClueBoy already mentioned, it hides imperfections.
Sheetrock’s gonna fail quicker on the horizontal surfaces than the vertical ones. Being it ain’t a structural part of the place, it’s okay if it cracks, but it could get ugly if it does too much.
Tripler
If you can see the crack, it’s already cracked too much.
Actually they are painted with the same paint used on walls, though ceiling paint tends to be a little cheaper and is generally pigmented white. This is not a problem as ceilings recieve very little wear and do not require a 20 year, scrub resistant finish, though you could certainly apply one if you wanted or had some extra paint lying around. I have.
The bumpy/ scratchy surface you describe is one of hundreds of texturing techniques used on ceilings. walls or anything where a smooth finish is not desired. These are generally either sprayed (spatter) knifed (scratch coat) or brushed (stipple). The material varies from high tech ceiling noise dampening compounds to plain ol’ dry wall mud.
The reasons given by the other posters are quite correct and there are others. The most common one is a textured surface does not require as much “taping” finishing to conceal the joints. This lowers the labor required to finish the job and thus the cost. Others I have heard are light refraction and finger print resistance.
I forgot to include that there are texturing compounds that can be mixed right into paint to create a one step rolled on application. My experience is that the finish is to “splotchy” and looks like crap. Explains why I still have a case of it taking up space in my shop. Also I left out the “popcorn” and “cottage cheese” accoustical finishes that are blown/sprayed on and left unpainted. That’s the stuff that falls into your coffee when the kids upstairs play their infernal rock and roll music too loud.
Wow, great responses and less than a day after my post. Thanks a lot everyone!!