Exterior Painting Preparation

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Yes, you guessed it... the exterior painting preparation step is at the top of the list of the all important steps when tackling a painting job for outside of your house.

A good paint job protects wood siding and trim from water damage and rot while it guards metal gutters, downspouts, and railings from rust and corrosion. And in preparing for a paint job, all the seams and joints in the outer shell of the house have to be inspected and recaulked. Remember though, Safety Comes First - especially the proper use of ladders.

No method is effortless. A certain amount of handwork - scraping, washing, and sanding - is required.

Here's a checklist for examining your house and planning exterior painting preparation work:

Wood Siding

• Make needed surface repairs and recaulk joints.
• Countersink bleeding nails and coat with metal primer
• Fill holes with putty
• Scrape and sand smooth
• Prime raw wood

Wood Shutters

• Remove from house and mark location on each.
• Scrub and sand smooth
• Work on shutters in garage or workshop when weather is bad

Windows

• Sand down wood, or wire-brush metal frames
• Replace missing putty
• Apply appropriate primer (rust-inhibiting for metal)

Doors

• Check weather stripping and replace if necessary
• Remove brass hardware and polish it; coat with acrylic lacquer to retard oxidation
• Scrape down flaking paint
• Repair cracks or hole with wood putty and sand smooth
• Apply primer to raw wood areas

Gutters and downspouts

• Check for leaks and clogs; make repairs
• Flaking paint should be wire-brushed off metal outsides to make a smooth surface
• Apply appropriate metal primer

Soffits

• Strip smooth with a wire brush and a sander
• Check for mildew and treat if necessary
• Apply primer to raw wood areas

Fascia boards

• Often behind gutters, they need sanding down to sound paint.
• Seal any knots
• Check for mildew and treat if necessary
• Apply primer to raw wood areas

Wrought-iron trim

• Sand down rust spots to bare metal with a wire-brush attachment on a electric drill
• Apply a rust-inhibiting primer

Exterior Painting Preparation - Wood Surfaces

Cracking and peeling paint are common on wood siding. It's time to put some elbow grease into the work and start the scraping and sanding. I recommend using a high pressure washer if there are more than 200 or 300 square feet of siding to prepare.

Using a High Pressure Washer

A professional pressure washer delivers up to 2,000 lb. per sq. in. of water power to remove loose paint from siding and shingles. It minimizes scraping chores and then cleans when detergent is added, which makes the exterior painting preparation much easier and quicker.

Hold the tip of the gun at an angle to the surface being blasted. This helps water lift paint off the surface.

The disadvantage to water blasting is that it leaves the wood saturated with water. You have to wait until the wood has dried completely before painting. A sweep with a high pressure blaster can inject water deep into old wood. It may be several days before this water finds its way back to the surface and evaporates. Paint too soon and you'll have a rapid repeat performance of the cracking and peeling paint job that you're attempting to remedy.

Check out my section for Pressure Washing Tips.

Sanding the Wood

Your next step for exterior painting preparation is to sand the wood surface. This creates a smooth, even finish and removes any old paint that was missed by the pressure washer.

Use a hand-held disc sander for this work. Sanding a large surface by hand takes too long and doesn't do as good a job as a disc sander.

On the first pass with the disc sander, use a rougher grade of sandpaper. Then finish up with a finer grade of paper. The grade to use depends on the condition of the surface. You may have to try a couple of grades until you find the right one. Note that rougher grade papers can gouge the wood. Be careful not to press too hard or dwell in one spot too long.

Hold the sander with both hands and move it in the direction of the wood grain - not across the grain. Wear safety goggles and a dust mask when using an electric sander.

Keep sanding until you have a smooth surface ready for finish paint. Clean off the sanding dust and debris first - a tack cloth does an excellent job of removing the dust that would prevent your paint to adhere properly.

New Wood Surfaces

Preparing a new wood surface is usually easier. But prep is still necessary. Start by removing all sap and wood splinters. Then sand in the direction of the wood grain. You may want to start with rough sandpaper. Final sanding should be with finer paper. Next, use a knot sealer to seal knotholes and areas where sap has accumulated.

All bare wood must be sealed with a high quality exterior primer before applying the finish coats.

Peeling Paint on Wood Siding

Excessive moisture can cause blistering, peeling, and discoloration.

Another important step in exterior painting preparation is to identify and eliminate any sources of the moisture. Water from rain, melted snow behind ice dams, or condensed water vapor may be getting into the siding behind the paint.

Check for leaks in roofs and sidewalls. Are insulation, vapor barriers, and ventilation adequate? Make sure moisture from a clothes drier is vented to the outside. Check for leaky plumbing or deteriorated caulking around a bathtub or shower.

Repair the blistered surface by removing all loose paint. All bare wood must be sealed with a high quality exterior primer before applying the finish coats.

Cross-Grain Cracking

After many repaintings with oil-base paint, built-up paint may get too stiff to stand the constant expansion and contraction of the wood below. The result will be cracked paint. The only remedy is to remove all paint down to the bare wood. Then prime the surface properly and repaint.

Exterior Painting Preparation - Metal Surfaces

Using a Wire Brush Attachment

A wire brush attachment for an electric drill speeds stripping of metal surfaces like aluminum gutters and downspouts and wrought-iron railings. Wear goggles and gloves to protect yourself from flying paint chips and grit.

Galvanized Surfaces

Avoid painting new galvanized metal surfaces until they've weathered for about six months. Galvanized metal comes from the factory with a residue of the manufacturing process and stain inhibitors that prevent good paint adhesion. Weathering tends to neutralize the surface, making it more ready to accept paint.

If you need to paint galvanized metal right away, wash the surface with a mild acid such as vinegar. Rinse it thoroughly. Then apply a proper primer for metal/galvanized surfaces.

Iron and Steel

When you're painting iron or steel, the most important thing is good surface contact. These metals rust when air and moisture get under the protective coating. That's why surface preparation is so important.

First, use a wire brush or power sander on the metal surface followed by a rinse with solvent. Then use a medium or slow-drying primer with good wetting characteristics.

If the existing paint is still in good condition, remove any loose paint and sand to feather broken edges around where the metal is exposed. Then spot prime before applying the finish coat.

Cleaning the Surface

Another important aspect of exterior painting preparation is to create a nice "clean" surface in order for the paint to properly adhere.

Pressure Washing

You can use pressure washers for general cleaning of large exterior surfaces such as siding. Most pressure washers can be used to apply cleaners, for example, a degreaser can be used to remove stains). You'll also find a variety of wands, brushes and other hose-end attachments for applying different types of cleaners.

Also called power washers, these machines send a high-pressure water spray to scour away dirt, grease, grim, chalking paint and other contaminants.

If you don't want to invest in a pressure washer, you can rent a gas-powered model from most tool rental shops.

Check out my section for Pressure Washing Tips.

Hose Brush Attachment

Using a hose brush attachment with an extension pole speeds washing painted surfaces.
Mix a solution of T.S.P. (or another heavy-duty detergent), chlorine bleach, and water. Rinse with clear water.

Without this treatment grease, dirt, and pollutions will keep new paint from adhering.

A Garden Sprayer

A garden sprayer also can be used in exterior painting preparation. It is ideal for treating mildew-infected areas with a 3:1 water-chlorine bleach solution (no detergent), which kills the fungus.

Don't rinse the area, but allow it to dry before painting. If mildew is not completely eradicated, it will reappear under new paint.

Protect Against Splatters

When doing any outside painting, protect your foundation plantings and nearby shrubbery with drop cloths, as a paint film on leaves and blossoms can keep them from breathing and may cause irreparable damage. Old cloths or even paper, anchored with weights such as stones or bricks, should be placed on paved walks, patios, driveways, etc.

Masking of windows with newspaper and masking tape minimizes clean-up, speeds the work and makes trim painting easier to do.

Windows

If window sash is in good condition it is only necessary to make certain that the surfaces is clean and that nay loose or blistered paint has been removed before starting the repaint job.

Windows are particularly prone to moisture problems because of the large glass area that acts as a condenser in cold weather, bringing a flow of water down over the bottom of the frame whenever the condensation reaches the extreme. The melting of ice on storm sash does much the same thing.

At this point, it is a good idea to replace old putty to stop annoying rattles as well as air leaks that make your home drafty in winter. Caulking around window and door frames should also be done now.

Ok, now that all of the exterior painting preparation is done, it's time to proceed with the actual exterior painting (finish/top coating).