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It's important to take the time of year into account when painting the exterior of your home, as very cold (below 40 degrees F) or very hot temperatures can ruin your paint job. Therefore, the best time to paint your house is in late spring or early autumn. Also remember to check the weather forecast to make sure there is no rain promised for the days you choose to paint. If you're lucky, the only real preparation you'll need to do before the paint job is to clean the surface of your house. Use a hose to wash down the walls and go over any stubborn dirt with a wire brush and some warm soapy water.  Alternatively, a power washer can be used to clean particularly stubborn dirt and remove paint flecks. Just be careful not to cause any damage to the home by setting the spray too high.  Remember to wash from top to bottom, and allow the surface adequate time to dry thoroughly before proceeding with the paint job. If there is any old, defective paint on the surface of your house, you will need to remove it before you can proceed. This includes any paint that is loose, blistered or chipped.  Failing to remove the old, chipped paint before you begin will prevent the fresh paint from properly adhering to the surface of the house. Use a wire brush or paint scraper to knock any loose paint free from the surface of the house and use a power sander (or a piece of sandpaper wrapped around a wooden block) to smooth any rough surfaces. If there are any heavy deposits of old paint that need to be removed, you may need to use an electric paint remover, which essentially melts the paint and then pulls it from the wall. Before you begin painting, you will also need to inspect your house for damage and make any necessary repairs. It may seem like an effort, but it will ensure that you're house looks its best once the paint job is complete.  Walk around the periphery of the house and look for split shingles and siding, rust, mildew, popped nails. Don't just look at the exterior walls, also examine under the eaves and around the foundation. Pay attention to areas around windows and doors where old caulk or putty may be missing or needing replacement.  Any rust will need to be removed and mildew will need to be scrubbed away. Cracked siding will need to be filled and sanded, loose caulking or split shingles will have to be replaced and leaky gutters and downspouts will need to be repaired. It's a good idea to figure out how much paint you're going to need before you begin painting. This eliminates the risk of running out of paint halfway through.  To estimate the amount of paint you'll need, measure the perimeter of the house and the height of the house (excluding any gable ends) and multiply them by each other. Divide this number by the square foot coverage indicated on the can of paint you plan to use. This will give you the quantity of paint (in gallons) you will need for a single coat. However, it is a good idea to add an extra gallon to that number for safety. To calculate the amount of extra paint needed for any gable ends, measure the width and height of the gable end, multiply these numbers, then divide by 2. This will give you the gable's square-foot dimensions, which you can then include in your paint estimations. Keep in mind that certain exterior wall surfaces - such as shingles, masonry and stucco - may need 10% to 15% more paint than smooth, flat walls with the same square footage. The application method may also affect the type of paint you need - airless sprayers may require up to twice as much paint (for the same wall dimensions) as brushes or rollers. In some circumstances, you will need to apply a coat of primer to the surface of your house before you can begin painting. Primer provides a good foundation for the paint and will help it to last longer, as it provides extra protection from the elements.  You will need to apply primer to certain distressed areas of the house, especially if your prep work exposed any raw wood or bare metal, or if you scraped away a lot of loose paint. You will also need to apply primer if you are painting new wood for the first time, or if you are drastically changing the color of your home. The type of primer you use will depend on the type of paint. If you plan on using latex paint, you will need latex primer. If you plan on using solvent-thinned paint, you will need a solvent-base primer, and if you use metal paint, you will need a metal primer. Choose a high quality exterior paint, such as 100 percent acrylic latex. This will produce a better color, dry faster and be more durable in the long run.  Look for paint with a higher percentage of volume solids, and opt for cans labelled "premium" or "super-premium" rather than choosing budget brands. Also put some thought into the color you choose for your house. Take the style of your home into account and make sure the paint color complements the roof material and any brick or stone accents. Consider getting samples of your top colors and painting swathes on an obscured portion of your home. Take a couple of days to see how each of the samples look in different lights and decide which ones you prefer. If you bought several cans of paint, you will need to mix all of the paint from individual cans together in one large container.  This is due to the fact that the color of different batches of paint can vary slightly, even if it's meant to be the same. Mixing them together ensures an even color. Hold on to the original paint cans though. That way, if you have any paint left over you can pour it back into the original cans and reseal it. At this point you should also cover the area around your home with drop cloths, to prevent any paint from getting on sidewalks or landscaping.

Summary:
Choose the right time of year. Clean the surface of the house. Remove any defective paint. Make any necessary repairs. Figure out how much paint you're going to need. Prime the surface. Choose your paint. Mix your paint.