A number of causes can lead to exterior paint damages. Before you repaint, you need to diagnose the cause of the paint damage. Once you have diagnosed and fixed the underline cause of paint damage, you may prepare the surface, select an appropriate paint or stain, and apply the finish, as explained below.
Diagnosing Paint Problems: Typical causes of exterior paint damages include improper surface preparation for painting, careless painting, use of wrong paint, and structural problems that can trap moisture in the wood.
Blistering: Blisters appear in paint when water or solvent vapor is trapped under the paint. To relieve the blister and find if its a water blister of a solvent blister, cut the blister open. If you find bare wood underneath its a water blister created by moisture escaping from damp wood, if you find paint its a solvent blister usually caused by painting in direct sunlight..
Peeling: Paint often peels and curls away form wood when its was applied over dirty or wet wood. It may also be caused by painting over loose old paint.
Alligatoring: A pattern of lines and cracks resembling alligator skin is results of the top coat being applied before the bottom coat was dry. Alligatorung may alo accrue when the paints from the bottom and top coats are incompatible.
Wrinkling: Wrinkles in paint are the result of previous careless painting. If paint is applied too thickly, the top surface dries too rapidly and the paint underneath droops down beneath the top dry paint.
Chalking: High quality exterior paint is designed to chalk so that when it rains, dirt form the surface will wash off. But chalking that comes off when you rub up against the surface indicates that the surface was unprimed or finished with poor quality paint.
Preparing the Surface: Wood surfaces must be clean, dry and in excellent condition before you start to repaint. Wash greasy or dirty wood with a mild detergent, and hose off. Let the wood dry before painting. Repair any damaged boards, trim, or shingles. Fix any structural damages that allows water to penetrate and may lead to blistering.
Use a stiff wire brush or paint scraper to remove any dirt and all loose, peeling or blistering paint. Where paint damage is sever, you should remove the paint down to the bare wood. Feather the edges of any remaining undamaged paint with medium grade sandpaper. Once complete you need to sand again with fine grade sandpaper. If the top coat did not adhere to a previous coat, use a medium grade sand paper to rough up the damaged paint.
If moisture is causing the pint damage, apply a water repellent prime with an oil-base prime coat. Cover with two coats of high quality paint after repairing the surface.
Applying the Finish: Apply a clear waterproofing sealer to the ends of all boards to prevent water from penetrating the wood. Brush a prime coat on any barer new wood. Where heat and humidity cause wood to deteriorate quickly, you should treat the boards with a wood preservative before sealing.
When the exception of redwood, cedar and southern reed cypress, the wood needs to be painted or stained to protect it from the elements. Use a matching finish with a 2-inch brush for trim and a 4-inch brush for wider surfaces. For larger areas you may want to use a 9-inch roller. Choose a fine nap for smooth surfaces and a think nap for textured surfaces of paint.
Exterior painting is best done in fair. dry weather with temperatures is between 50 degrees and 90 degrees F. Wait until the morning dew has evaporated and stop painting before evening dampness sets in or the paint may result in blustering. Don’t paint when conditions are windy or dusty, you may end up with debri in your paint.