Walls, ceilings and paneling require a slightly larger nap size of 3/8-inch; for lightly textured walls, decks and concrete, use a ½-inch nap; and for
Step #3: Understand Nap Thickness
⅜” - ½” (9.5-12.7mm)—For smooth and semi-smooth surfaces like drywall, painted or unpainted walls and ceilings. ¾” - 1” (19.05-25.4mm)—For semi-rough surfaces like wood, stucco or a textured ceiling. 1 ¼” - 1 ½” (31.75-38.1mm)—For rough surfaces like concrete block, brick, or masonry.
Short pile rollers are high density and provide good paint pick up. They are designed for use on very smooth surfaces like new walls or ceilings, smooth furniture or cabinetry as they leave a very silky smooth finish. Medium pile rollers have slightly longer fibre but are still high density.
Ceilings and Drywall - Medium 3/8″ roller covers work best. Walls, Wood, and Metal - Small 1/4″ roller covers or foam rollers will produce the smoothest finish. Light to Medium Textured Surfaces - Microfiber rollers are best. Smooth Surfaces - Use a white woven short nap roller for an ultra fine finish.
3/8-inch or ½-inch
These sizes are great to use on most interior walls as the length of their nap fibers can go over grainier surfaces.
A 3/8″ roller nap is ideal for most interior walls, metal, and smooth surfaces. A 1/2″ roller nap is excellent for drywall interior walls and ceilings. A 3/4″ roller nap is best for exterior walls and popcorn ceilings. A 1 1/4″ roller nap is reserved for the most textured surfaces.
Medium Nap (on average 11mm)
A medium nap is the most common roller thickness. They are designed to hold good amount of paint. The medium nap will apply an even finish to walls and ceilings around your home without splattering excess paint all over the floor.
A nap size of 3/16 to 1/4 inch is effective for painting with a roller on smooth surfaces, such as smooth wallboard, drywall, metal, and smooth plaster. A nap size of 3/8 to 1/2 inch is preferred for most ceilings and walls, acoustic tile, paneling, smooth concrete, textured drywall, and wood.
Many painters “break in” a roller cover by priming it with water or thinner. In our lab we never prewet a cover before painting. If you choose to, you must spin it out with five or six strong pumps so it is only lightly damp. Then take even more moisture out by blotting the cover with a paper towel.
Short pile (a thickness of 6-8 mm) provides great cover for smooth walls (including drywall) and flat surfaces. Medium pile (10-12 mm) is handy for lightly textured walls and ceilings but it can still be used on walls.
Quality 12mm nap rollers will apply an even paint film to your walls and ceilings and give you a great finish, without splattering paint all over you and the floor. Professional painters actually use 20mm nap rollers on ceilings, and 12mm nap rollers on walls.
Try to maintain a wet edge. When using a roller keep the open side towards the area just painted. Try to complete one full surface at a time. Paint in an even grid pattern from top to bottom.
Nap is the thickness of the fibres on the roller cover, also known as “pile.” The more texture your surface has, the thicker the nap should be.
If the surface is moderately textured, painted concrete or brick, or paneling, use a 1/2-inch nap. If the surfaces are heavily textured, such as popcorn-textured walls, concrete, or bare brick, use a 3/4-inch nap. If the surface is rough brick, cinderblocks, or painting stucco, use a 1-inch nap.
When choosing rollers, remember that the curl size is proportionate to the roller size. So, for tight curls, use small diameter rollers; for larger, softer curls use larger sized rollers.
Glossy paint: 1-1 ½ hours and 2 hours before applying the second coat. Semi-gloss: It takes roughly 1 hour to dry and 2 hours before applying the second coat. Matte Paint: 30 minutes to an hour for drying and 1-2 hours before applying the second coat.
Not Fully Loading the Roller
The roller needs to be fully loaded with paint to the core, otherwise you'll get air bubbles on your wall, resulting in “paint acne.” To avoid this mistake, roll back and forth on the roller tray until all bubbles are gone and the roller feels heavy.
Dabbing painters tape against the roller cover is an easy way to work free any extra fibers. Once your the cover is lint free you're ready to begin painting.
POSSIBLE CAUSE
Excessive brushing or rolling – applying a paint too rapidly – will drive excess air into the film. Use of a roller cover with wrong nap length. Applying a gloss or semi-gloss paint over a porous or unsealed surface.
Walls, ceilings and paneling require a slightly larger nap size of 3/8-inch; for lightly textured walls, decks and concrete, use a ½-inch nap; and for textured ceilings, stucco and masonry, use ¾-inch.
As a guide, use: 4” roller for glossing or painting emulsion in small, awkward areas. 9” roller for painting internal walls, ceilings, and exterior walls. 12” roller for painting vast interior and exterior walls.
Uneven paint can cause a space to look unfinished, whereas a well-painted smooth ceiling gives a polished feel. Patchy ceilings can also be caused by streaks from the paint roller, brush marks or stipple from an uneven roller.
Generally speaking, 6-8mm nap covers are used for gloss and semi gloss paints, 10-12mm nap covers for low sheen and flat paints on walls and 20-32mm nap covers for most paints on rough surfaces such as concrete or textured walls.