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Exterior painting essentials: prep, prime and paint


Author: NJR Steel
Article Views:3234
Categories: Construction, Renovation, Paint, DIY

A successful painting project is a 3-step process - prepping, priming and painting. All of these steps are equally important to ensure great results. This article provides exacting detail for every possible painting surface in every possible condition. By following these steps, you can spend more time enjoying the results and less time bringing the ladder back out to repaint.

Fibre cement

For fibre cement that has been previously painted, complete the following steps.

Surface preparation
  1. Remove any loose or peeling paint by gentle scraping or with a hand wire brush
  2. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  3. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  4. Scrub off dirt, chalk and treated mildew with a detergent and water mixture. Rinse thoroughly, or carefully power wash with plain water.

Note: If the siding is, or may be, cement asbestos, make no attempt to scrape, sand, wire brush, power wash or otherwise disturb the surface, as this may release asbestos fibres into the environment. Instead, simply apply a solvent based or latex sealer/primer recommended for exterior masonry surfaces, and once thoroughly dried, proceed with painting.

Also, if you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. Priming is helpful, but not necessary if the existing paint is in excellent condition, unless specified by the paint manufacturer. Prime if there is any sign of efflorescence or loose paint (remove it first).
  2. Use a quality exterior latex primer that is recommended for masonry surfaces.
  3. Do not leave the primer unpainted.

Painting
  1. Use quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

For fibre cement that has never been painted, but has been primed, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  3. Clean off any dirt with a detergent and water mixture, and rinse thoroughly. You could also clean the surface by carefully power washing it with clean water.

Note: If the siding is, or may be, cement asbestos, make no attempt to scrape, sand, wire brush, power wash or otherwise disturb the surface, as this may release asbestos fibres into the environment. Instead, simply apply a solvent based or latex sealer/primer recommended for exterior masonry surfaces, and once thoroughly dried, proceed with painting.

Priming
  1. Priming is recommended for maximum resistance to efflorescence and mildew, even if the surface is pre-primed.
  2. Use quality exterior latex primer that is recommended for masonry or fibre cement.
  3. Prime immediately after installation, or pre-prime before installation.
  4. Do not leave a primer unpainted.

Painting
  1. Use quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

For fibre cement that has neither been previously painted or primed, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  3. Clean off any dirt with a detergent and water mixture, and rinse thoroughly. You could also clean the surface by carefully power washing it with clean water.

Note: If the siding is, or may be, cement asbestos, make no attempt to scrape, sand, wire brush, power wash or otherwise disturb the surface, as this may release asbestos fibres into the environment. Instead, simply apply a solvent based or latex sealer/primer recommended for exterior masonry surfaces, and once thoroughly dried, proceed with painting.

Priming
  1. Priming is necessary to ensure maximum durability and resistance to efflorescence and mildew.
  2. Use quality exterior latex primer that is recommended for masonry or fibre cement.
  3. Prime immediately after installation, or pre-prime before installation.
  4. Prime all edges, including (where possible) those cut as part of installation.
  5. Do not leave a primer unpainted.

Painting
  1. Use quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

Brick

For previously painted brick, complete the following steps.

Surface preparation
  1. Remove all loose or peeling paint by scraping and wire brushing, or by power washing with plain water, taking care not to drive water into cracks or mortar joints. Wear eye protection, gloves and a dust mask.
  2. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  3. Scrape out and widen any cracks, brush out dust, and seal with 100% acrylic or siliconised acrylic caulk. Apply second layer after several hours if needed.
  4. Check mortar joints carefully and repair or re-point as needed. Wall and chimney caps must be sound and continuous; chimney flue should have a rain cover.
  5. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  6. Remove dirt, chalk, dust, residual paint particles, unbound sand, and treated mildew by scrubbing with detergent and water, and rinse thoroughly. You could also clean the surface by power washing with plain water, taking care not to drive water into cracks or mortar joints.

Note: If you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. After preparing the surface, apply an exterior latex primer for best durability, uniformity and resistance to efflorescence and mildew.
  2. Use quality exterior latex primer that is recommended for masonry surfaces.
  3. Do not leave a primer unpainted.
Painting
  1. After priming, use a quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

Wood

For wood or siding and trim that has previously been painted, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. Make any glossy paint look dull by sanding with fine (#220) grit garnet paper. Rinse properly. Wear eye protection, dusk mask and work gloves throughout.
  3. Remove dirt, chalk, etc. by scrubbing with detergent and water. Rinse thoroughly. You could also clean the surface by carefully power washing using plain water. Note that softer woods (such as old and weathered cedar and redwood) can easily be damaged by the high pressure jet of power washing.

Note: If you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. Priming is helpful, but not necessary.
  2. Some latex paints may specify the use of a primer if used over an oil-based paint.
  3. Use quality exterior latex or oil-based primer that is recommended for wood repaint surfaces.
  4. Do not leave a primer unpainted.
Painting
  1. Use top-of-the-line exterior 100% acrylic latex house paint in flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. Use a quality oil-based house paint if the surface has a build-up of old oil-based paints.
  3. Do not apply oil-based paint over latex paint.

For wood or siding and trim with flaking or peeling paint, complete the following instructions.

Surface preparation
  1. Remove all loose or flaking paint by scraping or careful wire brushing along the grain of the wood using a stiff metal wire hand brush. Wear eye protection, a dust mask and work gloves throughout.
  2. For wood shakes, use a wire hand brush with vertical strokes. Note that with a steel wire brush on cedar, all buts of steel wire must be removed to prevent discolouration.
  3. Feather sand any rough edges of the remaining paint. You can refresh the surface of old, weathered wood by sanding with medium grit (#120) sand garnet paper. Wear eye protection, work gloves and a dust mask.
  4. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  5. Remove dirt, chalk, residual paint and treated mildew by scrubbing with detergent and water. Rinse thoroughly.

Note: If you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. Prime areas where old paint has come off. For best results, prime the entire surface.
  2. Use quality exterior stain blocking latex or oil-based wood primer.
  3. Do not leave a primer unpainted.
Painting
  1. Use top-of-the-line exterior 100% acrylic latex house paint in flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. A flat finish will provide a more uniform appearance, whereas quality satin and semi-gloss finishes will be more resistant to mildew.
  3. Use a quality oil-based house paint if the surface has a build-up of old oil-based paints.
  4. Do not apply oil-based paint over latex paint.

For bare wood or siding and trim, complete the following steps.

Surface preparation
  1. New wood should be painted promptly (within a few weeks) because any weathering will reduce the adhesion of primer and paint. However, if the wood has been treated and is still a bit moist, it should be allowed to dry prior to painting. Once constructed, two weeks’ exposure to the weather should be adequate for most siding materials. Thicker timber may take longer to dry.
  2. Dull any shiny areas with fine grit (#220) sandpaper.
  3. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  4. Refresh the surface of any weathered wood by sanding with medium grit (#120) garnet paper along the grain.
Priming
  1. Apply a quality exterior latex or oil-base stain blocking primer.
  2. Apply a second coat if there is stain bleeding through the primer.
  3. Do not leave a primer unpainted.
Painting
  1. Use top-of-the-line exterior 100% acrylic latex house paint in flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. Two coats will enhance hiding, mildew resistance, sheen uniformity and durability.
  3. A quality oil-based or alkyd paint may be used (with oil-based primer), but quality acrylic latex will provide better colour retention, mildew resistance and long term crack resistance.

Cinder block

For previously painted cinder block, complete the following steps.

Surface preparation
  1. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  2. Scrape out and widen any cracks, brush out dust, and seal with 100% acrylic or siliconised acrylic caulk. Apply second layer after several hours if needed.
  3. Check mortar joints carefully and repair or re-point as needed. Wall and chimney caps must be sound and continuous; chimney flue should have a rain cover.
  4. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  5. Remove dirt, chalk, dust, residual paint particles, unbound sand, and treated mildew by scrubbing with detergent and water, and rinse thoroughly. You could also clean the surface by power washing with plain water, taking care not to drive water into cracks or mortar joints.

Note: If you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. Priming is helpful, but not necessary if the existing paint is in excellent condition, unless specified by the paint manufacturer.
  2. Prime if there is any sign of efflorescence or any loose paint (remove these first).
  3. Use a quality latex primer that is recommended for masonry surfaces.
  4. Do not leave a primer unpainted.
Painting
  1. Use a quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

For painted cinder blocks that are flaking or peeling, complete the following steps.

  1. Remove all loose or flaking paint by scraping or careful wire brushing along the grain of the wood using a stiff metal wire hand brush. Wear eye protection, a dust mask and work gloves throughout.
  2. If efflorescence is present, remove by brushing with a wire brush. Wear eye protection and gloves, and, if possible, identify and eliminate any source of water from behind the fiber cement that could have caused the efflorescence.
  3. Scrape out and widen any cracks, brush out dust, and seal with 100% acrylic or siliconised acrylic caulk. Apply second layer after several hours if needed. Check mortar joints carefully and repair or re-point as needed. Wall and chimney caps must be sound and continuous; chimney flue should have a rain cover.
  4. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  5. Remove dirt, chalk, dust, residual paint particles, unbound sand, and treated mildew by scrubbing with detergent and water, and rinse thoroughly. You could also clean the surface by power washing with plain water, taking care not to drive water into cracks or mortar joints.

Note: If you suspect the old paint to contain lead, do not attempt to remove the paint by scraping, sanding, power washing or any other method, as the poisonous lead particles will be released. Rather hire a qualified contractor to do the job safely.

Priming
  1. After preparing the surface, apply an exterior latex primer for best durability, uniformity, and resistance to efflorescence and mildew.
  2. Use quality exterior latex primer that is recommended for masonry surfaces.
  3. Do not leave a primer unpainted.
Painting
  1. Use a quality latex masonry paint or top-of-the-line exterior 100% acrylic latex house paint in a flat, satin, or semigloss finish depending on the desired appearance.

Aluminium siding

For coated aluminium siding, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. Remove dirt, chalk, dust, residual paint particles, unbound sand, and treated mildew by scrubbing with detergent and water, and rinse thoroughly. You could also clean the surface by power washing with plain water.
  3. Chalking on weathered aliminium tends to be deep in the factory finish, and a second treatment may be necessary if there is still noticeable chalk on the surface.
Priming
  1. Priming is generally not necessary if chalk can be removed as part of the surface preparation. For areas where chalk is stubborn and cannot all be removed, apply a solvent based exterior primer recommended for aluminium.
  2. Do not leave a primer unpainted.
Painting
  1. Use a top-of-the-line exterior 100% acrylic latex house paint in a flat or satin finish, depending on desired appearance. A flat finish will be much less revealing of dents and irregularities in the siding than a glossier finish.
  2. For best results, apply by spray.

Metals (other than aluminium)

For previously painted metal surfaces in good condition, complete the following steps. For a more detailed account of painting metals, please see How to paint metal surfaces.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. If any rust is evident, remove as much as possible with a wire brush. Wear eye protection, a dust mask and work gloves.
  3. Remove dirt, chalk, treated mildew, and loosened rust by scrubbing the surface with detergent and water, and rinse thoroughly. You could also power wash the surface with plain water.
Priming
  1. Priming is generally not necessary if there is no sign of rust or corrosion. All dirt and chalk should be removed during the preparation.
  2. If, however, there is rust of corrosion evident after the preparation, cover the entire surface with a latex or oil-based exterior corrosion inhibitive primer.
  3. Use oil-based primer if the old coating is a build-up of oil-based paint.
  4. For copper, brass, or other copper-containing alloys, use only a primer recommended for these materials lest the finish become discoloured.
Painting
  1. Use a top-of-the-line exterior 100% acrylic latex house paint that is recommended for your primed or painted metal. Choose between a flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. Direct-to-metal (DTM) gloss latex products may be used with or without primer for ferrous metals according to the manufacturer’s instructions. However, best results will be obtained by using a metal primer.
  3. Use an oil-based paint if the old coating is a build-up of oil-based paint.

For previously painted metal that is flaking, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. Remove loose or peeling paint by scraping or wire brushing. Wear eye protection, a dust mask and work gloves.
  3. If any rust is evident, remove as much as possible with a wire brush. Wear eye protection, a dust mask and work gloves.
  4. Remove dirt, chalk, treated mildew, and loosened rust by scrubbing the surface with detergent and water, and rinse thoroughly. You could also power wash the surface with plain water.
Priming
  1. Use oil-based primer if the old coating is a build-up of oil-based paint.
  2. Use two coats of primer for maximum corrosion resistance.
  3. For copper, brass, or other copper-containing alloys, use only a primer recommended for these materials lest the finish become discoloured.
Painting
  1. Use a top-of-the-line exterior 100% acrylic latex house paint that is recommended for your primed or painted metal. Choose between a flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. Direct-to-metal (DTM) gloss latex products may be used with or without primer for ferrous metals according to the manufacturer’s instructions. However, best results will be obtained by using a metal primer.
  3. Use an oil-based paint if the old coating is a build-up of oil-based paint.

For bare metal surfaces, complete the following steps.

Surface preparation
  1. Treat any mildew with a solution of three parts water to one part household beach, leaving it on for 20 minutes and adding more as it dries. Rinse thoroughly. Wear eye and skin protection throughout.
  2. If any rust is evident, remove as much as possible with a wire brush. Wear eye protection, a dust mask and work gloves.
  3. Remove dirt, chalk, treated mildew, and loosened rust by scrubbing the surface with detergent and water, and rinse thoroughly. You could also power wash the surface with plain water.
Priming
  1. Apply a latex or oil-based exterior corrosion inhibitive primer to the entire area.
  2. Use two coats of primer for maximum corrosion resistance.
  3. For copper, brass, or other copper-containing alloys, use only a primer recommended for these materials lest the finish become discoloured.
Painting
  1. Use a top-of-the-line exterior 100% acrylic latex house paint that is recommended for your primed or painted metal. Choose between a flat, satin, semi-gloss or gloss finish, depending on the desired appearance.
  2. Direct-to-metal (DTM) products may be used with or without primer according to the manufacturer’s instructions. However, best results will be obtained by using a metal primer.
  3. DTM gloss latex products may be used for ferrous metals with or without primer according to the manufacturer’s instructions. Better results are obtained with a metal primer.

Source: Paint Quality Institute


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