How to Paint Trim and Doors
Although it's important for the body of a house to look nice, pay special attention when painting the trim, windows, and doors. These elements attract the most attention and are the most vulnerable to paint failure because of all the joints where water can enter if the seal fails.
Roof and wall trim
After you prime bare wood, apply caulk along all open seams between trimboards. Allow the caulk to dry for the amount of time specified on the label before applying a topcoat.
Brushes are best for applying paint to most trim. A 2.5- to 3-inch angled sash brush is generally all you need, but if you have a lot of wide trim, you may want a 4-inch square brush, a pad, or even a mini-roller.
Choose a semigloss or high-gloss alkyd-based paint for doors, which get a lot of use and abuse. Latex enamel also holds up well. If the door was previously painted with a high-gloss paint, use a deglosser to dull the finish and clean the surface. If a wood or metal door has never been painted, or if you expose bare wood or metal by sanding, apply the appropriate primer.
To prevent drips and runs, remove the door and lay it flat on sawhorses.
Make sure that you paint the bottom and top of a wooden door. If you don't, moisture may enter the door and cause it to swell or warp. A convenient mini-pad paint applicator lets you paint the bottom edge without removing the door.
If the door has a flat surface, paint it with a 2- or 3-inch-wide brush, pad, roller, or sprayer. A roller typically leaves a stippled finish that may not be acceptable on surfaces when viewed up close. If you use a roller for speed, plan to backbrush.
If the door is paneled, use a brush and paint the panels first. Then paint the horizontal cross pieces (the rails), and finally paint the vertical pieces (the stiles). Paint with the grain as you do when sanding.
Paint failure is common on wooden garage doors, especially raised-panel ones, which have many joints where water can enter. Of course, run-ins with bicycles, basketballs, and Buicks don't help. After you remove all the loose paint and degloss the surface with deglosser or by scuff-sanding, prime any bare wood or hardboard panels. You must use an alkyd primer on hardboard panels, so plan to use it on the whole door.
After priming, carefully apply a thin bead of paintable caulk to the sides and bottom of each panel where it meets the door's stiles and rails (the vertical and horizontal members of the frame). For extra protection and better bonding, mix Emulsa-Bond into the first topcoat. If the existing finish is in good condition, you can apply one topcoat to the cleaned and caulked door. If the door needs scraping, repairs, and sanding, finish the primed door with two topcoats.