Powdery feel on paint film.

Due to:

1. Use of low quality paint.
   
   
2. Use of interior paint for exterior application.
   
   
3. Adultration of paint.

Recommendation:

1. Use primer before application of top coats to seal the wall. Therefore more latex will remain on the wall surface (not being absorbed) to give better binding properties.
   
   
2. Use a quality exterior paint as top coats to help weathering resistance.