the brick along the bottom of my house is flaking and staining whte.What could a possible cause be??
The white powder you see is more than likely efflorescence. The brick, stone, concrete block, mortar etc. contain water soluble salts that are the source of the white deposits.
These trapped salts are set into motion when water enters masonry. The water dissolves the salts and carries them through the masonry towards the surface. Sunlight and wind draw the water to the surface but as the water evaporates, the salts are left behind.
To stop the efflorescence now, you must stop all water from entering the masonry surfaces. If you stop the water, there is no transport medium to carry the soluble salts to the surface where you will see them.
Pressurized water can sometimes be used to remove or dissolve efflorescence.
An acid, such as diluted muriatic acid, can be used to dissolve efflorescence. Water should be applied first so that the acid does not discolor the brick itself. Following application, baking soda can be used to neutralize the acid and prevent any additional damage to the masonry. Muriatic acid is toxic, and contact with skin or eyes should be avoided.
A strong brush can be used.
After cleaning the brick can be treated with a siloxane silane/water repellent. They can also be coated with a new clear masonry sealer that bridges cracks up to 1/8 inch. Using these products in tandem virtually assures that you will stop water from getting into the masonry.
I would not try to do any remedial work until the weather warms up. You want days where the temperature rises to 65 F or above to get best results from the sealants and water repellents.
Hope this helps, good luck.