Bellingham, Wa. Home Inspector and Flourishing Efflorescence

  While inspecting homes in Bellingham, Wa. and Blaine, Wa., that are built on, or have garages that are built concrete slabs, I often find large areas of efflorescence growing on the slab floor.  These areas are indicators of moisture seeping through the slab, via water or water vapor intrusion, and carrying with it the mineral salts that are inherent to the slab or sub-strata.  These mineral salts are than left deposited on the floor either as a stain or as a powdery pile up to an inch high or more.  Most commonly seen as a white powder, they can range in color from pure white, to blue, to a rusty color.  Efflorescence is a natural process that occurs in all or most slabs and mortar via evaporation during the curing or drying stage.  Sodium, potassium, and iron oxide sulphates, and calcium carbonate and other minerals produce alkali salts that are caused to move through the porous areas of the slab in the presence of water.  However, this usually occurs during the first year of curing.  When we see continuing recurrence of efflorescence on older or well-cured slabs, this is an indication or implication of continuing water seepage or presence in and through the slab, mortar, or brick, in the case of brick walls.  This may be caused by improper or non-existent installation of a moisture barrier beneath the slab, which allows moisture to wick up into the porous slab, and transport the offending alkali salts with it.  There is no panacea or easy fix for this phenomenon.  Perhaps the best solution is preventive measures.  Utilizing low alkali portland cement, washing the rock and sand utilized in the mortar mix, and even coating the rebar to prevent rusting could make a difference in the amount of alkali salts.  Good luck if you can get a cement contractor to do any of the above. More important than anything is having a few inches of clean drain rock and a proper vapor barrier under the slab.  Short of this, there are a few products on the market that have been utilized to try and ameliorate the problem, ranging from acid washes to remove stubborn efflorescence, to silicon and epoxy sealers for moisture prevention.  Though they may prevent some moisture intrusion, silicon sealers for mortar walls could cause spalling, due to the different expansion rates of these alkali salts trapped in the bricks and mortar joints, and epoxy sealers for slabs may cause colored cements to discolor unevenly. The other implication of efflorescence in homes built on slabs is the possibility of excess moisture in the home, via water vapor. All of this amounts to more good reasons for a comprehensive Home Inspection and recommendations by a Bellingham, Wa. Home Inspector.     Allmann Home Inspection Services in Bellingham, Wa.     360-371-0260   

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