One drawback to having an exterior surface such as siding or window trim that must be painted is the constant exposure to the elements causes the paint to chip and fade, requiring you to repaint the surface every few years. A screened-in porch is no exception to this if sections of the porch are built with wood. If this is a new porch, it's much easier to paint the individual pieces before they are installed, but if you're repainting the porch, you must work around the screens.
Things You'll Need
Trisodium phosphate (TSP)
Spray the porch down with a garden hose to remove dirt from the surface. If there are any areas where the hose is ineffective at cleaning, mix a solution of trisodium phosphate and water and scrub the area with a brush before rinsing it with the hose. Allow the porch to dry.
Lay drop cloths along the interior and exterior of the porch to collect paint chips and prevent paint from dripping onto the floor or the ground outside.
Scrape away any paint that is flaking off with a putty knife, and sand the painted areas around spots where bare wood is exposed to smooth it out.
Turn off the power to any electrical circuits inside the walls being painted at your home's main electrical box, then remove any electrical outlet or switch overs that are on the wall being painted.
Place painter's tape along the outer edges of the screens if the frames are wooden and need to be painted, or on the edges of the frames if they're made of another material and are not being painted.
Apply primer to the wood. This must be applied to any bare wood, but you don't need to use it if the porch is being painted the same color or a darker color. Place the primer on the tips of the bristles to avoid applying too much and then apply the primer with smooth, even strokes. Allow the primer to dry.
Paint the wood, using the same technique with which you applied the primer. Allow the paint to dry, and apply a second coat if needed. Use an exterior-grade paint.