Whoever repainted the walls in this house did some quick mudding and sanding in places and not in others. The surfaces I'm now looking at vary from smooth to grooved to lumpy and any paint put on top of this will just look the same. Removing the drywall and starting again is a very last resort. I've noticed that the "bumpiest" surfaces are right above the radiators, so it begs the question; is there an optimum drying temperature for a smooth painted surface? My main question is how do I prepare an already (poorly) painted wall for a repaint?
Terry, There is a lot of what you describe in our house. This can happen when there is a time constraint on the paint job. Wall prep is left incomplete and paint application is started so as to complete the job by a specific time. In our case, wallpaper removal, poorly attached built-ins and wood paneling all have played roles in this. Sometimes an oil-based primer over the existing paint can smooth over smaller irregularities. All too often we have to skim coat large portions of the wall. This requires multiple coats of joint compound with overnight drying between coats. Add in the sanding mess so you can see why it's easy to skip this. If you opt to replace drywall you'll still have to tape the joints and mudd the screws so you may not save much time. Plus you'll have to transport the new drywall and dispose of the demo. If other forum contributors have better ways to solve this problem, I am also very interested.