Largo Green (LG) solved the mystery of where water leak originated. Balcony slate tiles were cracked & mortar was damp underneath. Real culprit was the metal flashing that was rusted through, allowing water penetration at common wall & down into Client's attic. LG removed old mortar, flashing, siding, & tiles. LG applied thick moisture barrier, then a thick 2 coats of lacquer sealer.