Exterior painting

At first, you may think the process is easy: simply buy exterior paint. Although the exercise doesn't have to be complicated, there are rules to follow and tricks of the trade to remember.
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Picking the right time
Preparing and planning your work
Prime for a successful job
Paint or stain?
Wood surfaces
Painting wood
A particular attention to non-treated wood
Prefinished siding
Painting prefinished siding
Concrete surfaces
Painting concrete
Wrought iron
Painting wrought iron
Safety

Picking the right time

What season? Certain weather conditions such as excess humidity cause paint to crack; frost can take the shine out of the paint while a hot sun will cause the paint to blister. Ideally, you should paint in the spring or fall when these factors are less important and while trees and bushes have no leaves. In a pinch, you can paint in summer, if it's not too hot, making sure you stay ahead of the sun as it goes around the house.

What time of the day? Be careful in selecting the time of day during which you want to work. Among other things, early morning dew can result in devastating humidity that causes paint to lose its gloss or peel. So wait for the temperature to rise and for the dew to dissipate. In the afternoon, you should stop work early enough for the paint to dry before the dew returns.

Preparing and planning your work

Before launching into a painting project, it's important to prepare the surface.

First, it must be dry and contaminant-free. Whether the contaminant is grease, soot or chalking, it must be removed to allow the new paint or stain to adhere to the surface evenly and properly. To remove dirt, use a trisodium phosphate (TSP). A chlorine-based cleaner will do wonders with mold. Always scrape away peeling paint and finish the job with a good sanding. Any wood exposed as result of this preparation should be primed.

You should start from the top of house by painting large surfaces first: cornices, then siding, from top to bottom, followed by windows and doors, keeping shutters, storm windows and removable mosquito screens for the end - or saving them to be painted in the garage on a rainy day. You can then finish with balconies and patios.

Prime for a successful job

Primer plays a critical role in painting. And there are different types of primers suited to different types of paint jobs. An alkyd or latex-based primer is recommended for solid wood, shingles, exterior house walls, doors, windows, trim, fences, etc. Latex primer is especially recommended for hardboard siding and patios because it prevents superficial splitting and cracking of plywood.

Paint or stain?

The answer depends on the effect you ultimately want. Paint is opaque and offers a near-infinite choice of colours. Stain can be either semi-opaque or opaque but offers a more limited range of colours. In the end, the choice is yours to make and depends on the existing surroundings.

Wood surfaces

Paint is meant to cover surfaces and give them colour, not hide their faults. Over the years, if the wood was not prepared properly, the paint may have peeled. Depending on the extent of the problem, you can simply remove the peeling paint and repaint, or strip the house completely. In the first instance, you should use a scraper and a rigid putty knife. But bear in mind that removing peeling paint will leave cavities that have to be spackled and smoothed with an electric sander. But that shouldn't take much time.

The more serious cases may require that you strip the entire house. That may also be necessary in the case of a surface that is not that badly damaged but is in full view. To heat-strip the paint, use a propane torch. First heat the surface until the paint softens and shrinks. Then scrape it with a putty knife. If the wood turns brown, don't worry. But don't scorch it! If you're afraid of using a torch; a electric paint stripper will also do the trick, although more slowly. Whatever you use, be sure to have a fire extinguisher close at hand.

Not all exterior painted wood peels. So, if the surface is still in good shape but could use a new coat of paint or if you'd like it in a different colour, you can paint it without doing much more than cleaning it with a solution of trisodium phosphate to remove dirt and chalking.

Painting wood

We suggest an exterior acrylic latex paint for wood siding. Acrylic paints are more resistant to humidity and discolouration than alkyd paints. We recommend the same paint, for the same reasons, for cornices. It can even be used for doors and windows although exterior alkyd paint offers more resistance to friction.

A particular attention to non-treated wood

Wood that hasn't been factory-treated is especially vulnerable to water and humidity damage. This is particularly true of untreated windows, window sills and pine door frames which require a preservative to ensure in-depth protection against rot. Two types of such preservatives are available: zinc or copper naphtenate. Zinc naphtenate is clear while copper naphtenate is tinted in green.

Prefinished siding

It's possible to repaint vinyl, steel, aluminum or hardboard siding. But before proceeding, you must sand all surfaces. Then, wash the siding with a concentrated solution of trisodium phosphate. If it's a vinyl siding, you're ready to paint. For other types of siding, you must scrape any peeling paint and smooth out the area by sanding. Any steel exposed by this process must first be treated with a zinc chromate yellow primer. Any part of hardboard siding that has been exposed must be treated with oil before repainting.

Painting prefinished siding

We recommend acrylic latex paint, in a matte or semi-gloss finish for vinyl siding. For hardboard or aluminum siding, we suggest either exterior acrylic latex or alkyd paint. For steel siding, you should use a rust-inhibiting acrylic or oil paint. Either way, you'll need two coats.

Concrete surfaces

There are two things to watch for on stripped concrete: efflorescence and oil stains. Efflorescence stains are white and are caused by the mineral salts found in concrete. To remove them, use muriatic acid, making sure to follow the manufacturer's instructions.

As for oil stains, you must not attempt to clean them using a solvent as this will cause them to penetrate more deeply into the concrete. Rather, cover them with dry Portland cement for about 12 hours. And repeat if necessary. If the concrete surface has already been painted, remove any peeling paint with a steel brush. Before repainting, wash thoroughly. Proceed in the same fashion for brick walls.

Painting concrete

Concrete foundations or exterior walls can also be painted using an exterior acrylic latex paint. Be sure to wet the concrete before applying the first coat. For concrete floors, use an epoxy-based exterior paint, the same kind of paint that is used for outdoor balconies. And please follow the manufacturer's instructions.

Wrought iron

First, you must scrape off rust blisters with a double-bladed, reversible scraper. When you find the first side of the blade a bit worn off, turn it around. Then, clean the surface with a steel hand brush or with a circular steel brush mounted on your electric drill. Either way, wear protective glasses. When all of this is done, clean the surface before repainting.

Painting wrought iron

Once cleaning is completed, apply rust-inhibiting primer and exterior enamel. If you use rust-inhibiting paint, you don't need to apply the primer. Either way, you will need two finish coats.

Safety

The use of ladders requires certain precautions. The base of the ladder should be set away from the wall, at a distance equivalent to one quarter of its height. So, if the top of the ladder is 12 feet off the ground, the foot of the ladder should be 3 feet away from the wall. And if at all possible, tie the foot to the side of the house.
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