One of the main problems you'll have to contend with when applying exterior house paint is paint bubbling. Painting the exterior of a building on a sunny day can cause the paint to dry too quickly. Heat vapors that become trapped inside the fast-drying paint begin to expand. The expanded vapors cause bubbling under the paint.
Dark colors of exterior paint can absorb more heat and consequently have more bubbling problems than light colors of paint. Moisture can also cause bubbling problems in exterior paint. The moisture can become trapped under the paint and cause it to expand. Moisture problems can be caused by the weather and by faulty overhangs and gutters.
Be sure to put on your protective eyewear before you begin your work.
Open the Paint Bubble
Use a scraper to carefully open the paint bubble. Inspect the inside of the bubble. A moisture problem would result in unfinished wood behind the bubble. Heat problems will result in a visible layer of paint behind the bubble.
Solve Moisture Problems
Find the cause of any moisture or heat problems you might have and, if possible, fix them immediately.
Wait for the Paint to Dry
Allow the surface about two days to dry. It is difficult to remove bubbles from wet paint.
Remove the Bubbles
Use the scraper to remove all the visible bubbles and any loose paint. Use the sandpaper to smooth the bubbled paint area and 12 inches of the surrounding wall.
Clean the Paint
Fill a bucket with warm water. Add three squirts of liquid soap to the water. Combine the contents to make a warm, soapy solution. Immerse the scrub brush into the bucket. Shake off any excess water. Use the scrub brush to carefully clean the area. Use the garden hose to rinse the area with water.
Apply a Water Repellent Sealer
Read the instructions provided by the manufacturer before you apply the sealer. Following the directions, use a paintbrush to apply the water repellent sealer to the wood to prevent any further moisture problems. Allow the sealer two days to dry completely.
Apply a Primer
Read the instructions provided by the manufacturer before you apply the primer. Following the directions, use a paintbrush to apply a primer to the area. Allow the primer about two days to dry completely.
Repaint the Area
Repaint the smoothed and cleaned area on a cool or overcast day. Read the instructions provided by the manufacturer before applying the paint. Following the directions, use a paintbrush to apply a thin coat of paint to the area. Allow the paint enough time to dry completely. Continue painting thin layers over the area and allowing the paint to dry until the entire area is fully covered.