Painting modern substrates
Many newer exterior products, ranging from siding material to railings, columns, windows, stairs, and decks, are made to stand up to the elements. Most of these products may be successfully painted to:
-- Alter the color
-- Change selected colors to complement trim and other elements
-- Refresh the appearance or change the degree of gloss or sheen
-- Enhance the protection of the material
Preparation steps are generally the same as for other surfaces -- treating mildew, cleaning dirt and dust, removing white, powdery oxide with a nonmetallic scouring pad, and lightly sanding glossy areas with 220-grit sandpaper (but do not expose any metal substrates). Painting, likewise, is best accomplished with exterior acrylic latex paint. Apply a flat sheen on dented surfaces.
Some of the most common materials and problems include:
-- Factory-finished aluminum materials usually have a powder coating and a glossy finish. After years of weathering, released pigment may chalk the surface. For uniformity prime the area, including the factory finish.
-- Vinyl and PVC materials, including polymer/wood mixtures, can release pigment chalk after years of weathering. Avoid painting rigid vinyl, especially vinyl siding, with a dark color, because the color may absorb the sun's heat and warp the panels irreversibly. As a rule, you should not paint vinyl siding any darker than its original color. Do not attempt to paint any material if the manufacturer recommends against it.
-- Polyester, fiberglass, and synthetic (polymeric) stone materials, generally molded or cast with mineral fillers such as limestone, talc, or clay may also chalk after years of weathering. For best adhesion and uniformity, apply a quality latex stain-blocking primer recommended for this material. Don't apply oil-base or shellac-base primer. For exterior furniture, use a quality exterior latex satin or semigloss product.
-- Fiber cement siding, a high-density material made from cement and fiber and formed into siding and soffits, is supplied factory primed, to be painted prior to or after construction. It sometimes comes with a factory-applied color finish coat. Seal all cracks and openings with a quality acrylic or siliconized acrylic sealant. Do not seal side or bottom edges unless directed by manufacturer. Remove loose paint by careful power washing with plain water. Apply a quality exterior latex stain-blocking or masonry primer recommended for this material. Apply exterior acrylic latex paint recommended for masonry surfaces.