There are a few problems at work on this once beautiful Sandstone exterior facade. First, a silane impregnator was used to protect the caulk joints at the time of construction. Amazingly, the impregnator used adjacent to the caulk joints, still repels moisture and dirt 12 years since installation. This is what gives the sandstone a checker board look with every rain. See original building in 2002 (below). Another issue is the roof flashing was installed improperly, causing drainage down the wall. Because the face of the sandstone has not been maintained, and a quality impregnating sealer like HMK S31 Silane Impregnator was NOT used, this is why the sandstone has stained and will require an extensive and very expensive restoration. This could have been prevented if properly protected, and regularly maintained.
If you are an architect, or building developer, and need more information about how to develop a stone protection and maintenance plan, please contact www.StoneCareOnline.com at 800-380-6881 or Email us at firstname.lastname@example.org