What is the white build-up that forms on my concrete and masonry?

The white mineral build-up is called efflorescence. It is caused when minerals leech to the surface from within the brick, block or concrete. This occurs more during a rainy seasons or in an area that gets a lot of water from a sprinkler. If the stain does not wash away easily with water, use a cleaning solution of 1 part vinegar to 5 parts water and a stiff nylon brush. You should be able to scrub most of the efflorescence off. After using the vinegar solution, rinse well with water. At this point if there is damage that needs to be repaired you can use a product called Thoro Seal from Cohill’s Building Specialties.