This is called “efflorescence” and it is a sure sign of dampness in concrete walls. Moisture coming through the walls from the soil surrounding the building foundation causes a chemical breakdown of the bonding agent in the concrete. The white substance is free lime leaching out of the wall. Efflorescence weakens the concrete, and if ignored, can eventually compromise the structural integrity of the wall. If you notice efflorescence on your unfinished basement walls, give DrainCom a call. We can suggest a number of treatments that can be applied to stop the efflorescence by reducing the dampness at the source.