Application

The painting system and type of coating is selected based on the surface material and area of working. There are different considerations for wood, metal, masonry, or other interior and exterior surfaces. Usually, manufacturers of building materials have recommendation for the desired coating. The process of paint application includes preparing the surface or substrate, protecting adjacent surfaces, preparing the paints, applying the primer, sealing and filling cracks and joints, and applying the topcoat paint.

Preparing the surface includes cleaning, repairing, and pretreating (if necessary). Detergents, solvents, and chemical treatments are some materials used for cleaning surfaces. Different types of surfaces may need specific preparation. For any surface, proper detergent or solvent is used to clean the surface from any contaminants. All surfaces should be dry and vacuumed to remove any dust. It is important to properly seal the spots and stains as well as fill any hole and crack on the surface. The painting surfaces in a building are wood, metal, plaster, drywall, masonry or cementitious, and synthetic.

Wood surfaces should have moisture of 15% or lower. Sunlight may cause some ultraviolet damages in the wood, so the new wood should be primed shortly. Concrete surfaces need at least 28 days to finish curing concrete. ASTM D-4258 is a standard practice for cleaning concrete. Laitance and efflorescence should be removed from the surface. For steel surfaces, it is important to remove slag, flux, weld spatter, and rough edges. Any contaminates including rust, dirt, mill scale, and old paint should be removed from the surface using hand tools, power tools, blast machines, or water jetting machines. For drywall surfaces, joint compound is used to cover nail and screws in the attachments and seams. The joint compound should be dried and sanded before coating. In case of plaster surfaces, if any panel was loose or broken it should be repaired, replaced, or hardened with a white vinegar wash. The surfaces should have moisture of 6% or lower and its alkaline level should be neutral.

Sealants are used to protect the surface from moisture, air, and heat. Fillers are applied to the substrates to fill any holes, cracks, tears, and other spaces. Caulking is a general term to describe any sealant or filler that is available in cartridges. Caulks and putties are actually those sealants and fillers used on construction joints. Sealant may apply on different surfaces such as wood, metal, and, ceramic. They are usually applied after the primer and before topcoat painting.

Preparing the paint is to provide uniform color and consistency. It is done by mixing all the components properly. All surrounding surfaces and areas should be protected to avoid any demand. In painting with a brush, the bristle is immersed in paint container halfway and the paint is applied to the surface. For applying paint with rollers, after loading enough paint to the roller cover, it follows zigzag patterns like the letter N or M on the surface.

Panting interior surfaces should begin from a corner of the ceiling. It will start from the top toward the bottom. In case of multi-coating, the existing layer should be dry before applying the next coat. Cutting in and trimming is done with a brush tool and the surface coating is applied with a roller. Cutting in is painting corners and the perimeter of windows and doors before using roller. The reason for applying cut in layer is to keep the wet edge and prevent lapping. Keeping wet edge is to start the unpainted area when the adjacent painted surface is still wet. The reason is to avoid lap marks and feather the edges. The roller should be applied on the cutting area to make the uniform texture all over the surface. After ceiling is done, wall painting is started. The coating is from top of the wall to the bottom and usually from left side of the room to the right.

Exterior surfaces follow the same method as the interiors. It is common to start from main wall surfaces. Other painting areas are trim, railings, porches, steps, and the foundation. The environmental condition should be ideal for painting. Temperature should be in an accepted range, suggested by the manufacturers. Sunlight should be enough to dry the surface but not too much to make it dry too fast. Rain or strong winds may cause some damage or stain in the painting surface. Same as interior walls, rollers are used for painting large flat surfaces made from brick, stucco, concrete, or masonry. For overlapping siding such as clapboards or shingles, first a brush is used to cover bottom edges. Next the rollers cover the top surface. The painting starts from a painted wet siding to the adjacent unpainted surface. The surface is coated with smooth, even horizontal strokes. The final brush stroke should be vertically along the grain of the wood.