Expert: Bruce E. Johnson - 7/8/2009

Question
Dear Bruce,
   I have an interior, concrete-block wall on an attached garage.  There are 3 courses of block above the floor level. On the other side of this wall is a family room on a slab. The block face on the garage side of this wall has been slowly eroding over the past 20 years, in minute quantities, onto the garage floor.  
   It appears as though a chemical reaction has been taking place, because the block has a white, frosty look to it.
   I'd appreciate any advise you could give me to remedy this situation.
   Thanks!


Answer
Hi Allen, it sounds like you have a water intrusion problem.  I am a bit confused as to where this wall is located.  It almost sounds like it is an interior wall.  If this is the case then you have a water leak either in your plumbing or roof.  The white frosty stuff is called efflorescence and is caused by water interacting with the lime in the cement in your mortar.  It can be removed by sand blasting or other means but you really need to identify where the water is coming from and fix that problem. I hope this information helps, feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com