GUIDELINES FOR EXTERIOR REPAINTING by Michelle Probert, Technical Representative, MPDA

Preventative maintenance of your property includes a regular repaint program to repair, touch-up, or apply full coats of paint before deterioration begins. If your strata council is considering repainting in the near future there are many considerations to take into account. The following information is a guideline to help you understand Exterior Maintenance Repaint procedures.

Paint, the most important factor in the protection of a surface, serves as a protective shield between the base construction materials and the elements that attack and deteriorate them. Typical causes of failure are moisture, temperature variations, sunlight, fresh and salt water, water vapour, rot, mildew, chemicals and abrasion. Through the application of paint or other protective coatings, the useful life of a structure will be extended and protected against these attacking elements that cause failure. Most surfaces should be repainted every 5 to 7 years to properly protect the underlying components.

Site Assessment

The first step to be taken is an inspection and assessment of your buildings to create a list of substrate components and to determine the present condition of the existing paint and coatings. Faded, discoloured and peeling paint are good indicators that new paint is required.

Examples of substrate components may include dimensional or dressed lumber, wood panels, stucco, concrete, brick, and ferrous or galvanized metals. Make note of all the paintable components of the building's exterior surfaces to create a repainting maintenance checklist. The condition of the substrate, the existing coating to be repainted, and the intended finished appearance are all factors when assessing for new paint. Many surface defects can be remedied with the proper preparations and paint applications; however surfaces that are severely damaged should be repaired or replaced prior to painting.

Each surface is unique and a quality paint job is reliant on the selection of appropriate paint systems and performing the proper preparation prior to the application of the primers and topcoats.

Surface Preparation

All surfaces must be properly prepared to receive protective coatings since the performance of the new coating is directly related to the condition of the surface to which it is applied. Without proper surface preparation your painting project may end up with a poor result and sometimes even a complete failure. The majority of all coatings failures can be directly attributed to inadequate surface preparation that affects coating adhesion and performance. Surfaces are generally considered prepared for paint once they are clean, dry and dull.

Mildew, a general name for a variety of fungal species of the family, is often mistaken for dirt when seen on painted surfaces and requires complete sterilization with a bleach solution. Mildew treatment is performed prior to cleaning the surface using high/low-pressurized water.

Pressure washing has become a popular method for removing loose flaking paint, dust, dirt, and surface chalk but has its limitations as to the degree of cleaning obtained. Only properly trained qualified personnel should operate this equipment as improper use of the equipment can cause substrate blasting damage, or excessive moisture injection into (and even behind) the substrate. Some surfaces require hand washing/scrubbing to effectively remove surface residues.

Once the surfaces are clean and dry the next step is to remove all loose, non-adhering materials by scraping, grinding or sanding. Sanding with a suitable abrasive should dull glossy paints. Any filling, patching, and caulking is usually performed after the prime coat applications and should blend with adjacent surface and not be noticeable.

Primers

The first coat of paint is called the "prime coat" and, like surface preparation, the prime coat is an equally important part of the paint system. Primers are formulated differently than finish coats and their main purpose is to seal the surface, adhere to the underlying surface, protect the substrate, and aid in the adhesion of coats of paint applied on top.

It is important to understand that specific primers are manufactured for wood, concrete/masonry, plaster/drywall, various metals, and other miscellaneous substrates. For example, bare wood is generally primed with an oil/alkyd wood primer whereas a ferrous metal requires an anti-corrosive metal primer. It is also important to ensure that the primer is compatible with the existing and successive topcoats.

The level of priming will be dependant on the condition of the surface. For example, previously painted wood siding that is well sealed and reasonably sound may only require "spot priming" at areas of bare exposed wood whereas new exterior wood being replaced should be primed on all six sides with an exterior oil/alkyd primer prior to installation.

Finish Coats

The choice of finish coats and the degree of gloss will depend on the surface being painted, the level of protection needed, and the desired look to be achieved. Acrylics, latex, oil, alkyds, urethanes, …the choices are many! The difference between all these paints is their main resin (that's how paints are named) and they all perform differently. A site specific assessment must be made to determine which type of paint is the appropriate finish for the surface you want to coat.

Architectural coatings are also available in various gloss levels. "Flat" finishes are used widely on exterior wood siding and stucco as they help create a uniform appearance and help minimize surface defects however they are not recommended for surfaces exposed to constant contact as they pick up dirt easily and are easily marked or stained. "Semi-gloss" finishes offer good washability and abrasion resistance and are often used on doors and trim pieces. "Gloss" paints offer the greatest amount of protection but are principally only used on very smooth surfaces as they are highly reflective and show all surface defects.

Application

The application of new paint should cover the surfaces satisfactorily and provide solid coverage. Budget paint systems that use only one full finish coat may not adequately hide if there is a colour contrast between the old and new. Consideration should also be given to the application methods employed by the painter. While spray painting can apply paint quickly, this method requires a large amount of "masking off" and covering up to protect adjacent surfaces not scheduled to receive new paint. The coating of sprayed paint tends to "sit" on the surface and does not penetrate into porous, rough, or irregular surfaces. It is often recommended to follow spray paint applications immediately with a "brush and roll" method to work the wet paint into the surface and assist in an evenly applied coating. Coatings should be applied free of skips, voids, sags, drips, with sharp cut in lines and have an overall uniform appearance.

Environmental Conditions

Environmental and substrate conditions during exterior painting can dictate the success or failure of the paint system. Temperature and humidity during the application are very important to the coating's film formation, which controls adhesion, penetration, durability and appearance. In general, most coatings require a minimum temperature of 10ºC prior to and over the total drying period of the paint. Possible changes in weather conditions should be considered as rain and dew will damage freshly applied coatings and the application of paint in direct sunlight or onto hot surfaces should also be avoided. Minimal environmental conditions should be present before, during and after the coating applications. Testing of substrates should be performed to ensure acceptable levels moisture and/or Ph levels are present immediately prior to any coatings applications.

Contracting the Work

The Master Painters and Decorators Association (MPDA) strongly recommends that a site specific repaint specification is prepared prior to tendering the work to for an "apples to apples" comparison of bid prices. A proper specification will outline precisely the work and methods to be used including the paint systems for each substrate, the preparation and application methods to be employed, quality control and assurances, and all bid requirements/submittals such as bonding, insurance and references. The MPDA also recommends that the work performed by the Painting Contractor be reviewed by a qualified independent 3^rd party paint inspection agency to ensure all work complies with the specification.

Maintenance

A quality paint job will protect a substrate from accelerated weathering but it also needs to be maintained to protect the integrity of the paint. Visually inspect the various exterior components of your building every 6 to 12 months and look for indicators of surface degradation such as mildew growth, discoloration, peeling paint, cracking of masonry surfaces or rusting metals. Once identified, isolated areas can be remedied and easily maintained.

So keep your buildings looking smart! Paint, when utilized properly will lower maintenance costs, help protect your investment and keep your building exteriors looking great for the years to come.

The Master Painters Institute (MPI) has published technical manuals that are recognized as the Painting Industry Standards in Canada and the United States. The Maintenance Repainting Manual outlines paint systems for Interior/ Exterior substrates and includes identifiers, assessment, surface preparations, and an "Approved Products List" of quality paint/coatings which have been tested and meet MPI standards. For more information contact the Master Painters and Decorators Association of British Columbia.
Phone: 604-298-3875