Advice and Tips

Exterior

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Popular Questions - Exterior

Aluminum Siding

+Q. What type of paint should I use to paint aluminum siding?

A.

In general, use a top of the line exterior 100% acrylic house and trim paint in a flat or satin finish. This assumes proper surface preparation, including removal of dirt, chalk and mildew. Unless metal is exposed, no primer is needed. If bare metal is visible, remove any white oxide with a non-metallic scouring pad such as ScotchBrite, then wash off and rinse, then apply a latex exterior corrosion inhibitive primer to the exposed metal area. As for the paint, use a flat if the siding is at all uneven and/or dented (while the satin finish will provide a rich, fresh appearance, it will accentuate the dents.

+Q. After removing the old chalky white from aluminum siding, I was told to wipe the siding with mineral spirits before priming it. Is this a necessary step before washing it? I had to use a sander to remove the road salt and the siding was badly pitted.

A.

No, unless you have some oily contaminant such as road tar on the siding, do not use mineral spirits. The road salt that you removed was probably white aluminum corrosion (aluminum oxide). After you clean and rinse the surface, you will need to prime all areas of exposed aluminum (that is, where you can see the metal), or where any of the white salts were.

For the primer, use a latex corrosion-inhibitive primer. Ask for this at a paint store. You may find it just as easy to prime all of the siding, rather than just the areas mentioned. If you do prime everything, you will get a more uniform appearance from the paint, compared with if you only prime some parts. For the paint itself, use a top of the line 100% acrylic latex house paint in a flat finish.

+Q. How should I prep old aluminum siding before painting? What type of primer is the best for siding?

A.

Remove as much "chalk", dirt and mildew as you can. This is done by power washing or by scrubbing and rinsing. The only times a primer would be needed are:

  1. if any bare aluminum is exposed; then use a latex corrosion-inhibitive primer;
  2. if there is still much "chalk" left on the surface, apply a quality exterior alkyd ("oil-based") primer recommended for aluminum siding by the manufacturer. ("Chalk" is powdery pigment on the surfaced of the weathered siding, that comes off when you rub the palm of your hand over the surface.)

Film Thickness

+Q. Why do you keep referring to applying the paint or stain at the spread rate [square feet per gallon] recommended by the manufacturer? Is it really that important? Isn't it reasonable to try to get extra "mileage" out of a gallon of paint?

A.

It is important because how thick or thin the coating is applied impacts many properties. This applies to paints, primers, stains, clear coatings and elastomeric coatings. Some properties directly impacted by spread rate (and thus film thickness) are:

  • Hiding and Uniformity of Appearance
  • Crack Resistance
  • Mildew Resistance
  • Stain Blocking (primers)
  • Corrosion Resiatance (primers)
  • Flow-Out and Smoothness (which affects appearance and durability)
  • Scrub Resistance
  • General Longevity of Protection While hiding may, for example be acceptable when a coating is spread thin, other properties can be seriously compromised.

Aluminum Windows

+Q. Can aluminum storm windows without a previous finish be painted? If so, what is the procedure?

A.

Yes, you should be able to do this successfully.

  1. Clean off any dirt, mildew, etc. by scrubbing with detergent and water, then rinse.

  2. Look for white powdery oxide, especially likely to be on the exterior surfaces, and scrub off as much as possible with a nonmetallic scouring pad like ScotchBrite. Rinse off.

  3. Apply a water based corrosion inhibiting primer. Put it on in a full coat, don't spread it out thin. Allow to dry over night.

  4. Apply a top of the line acrylic latex exterior house paint, flat, satin or semi gloss, depending on appearance wanted.

Avoid painting surfaces that will come in contact with each other. Use masking tape on glass; carefully remove it as soon as the paint has dried to touch. Don't paint if the outside temperature has been below 50° F in the past 24 hours, or is predicted to drop such, in the next 36 hours. Don't apply the paint in direct sunlight.

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