Abstract: A moisture detection apparatus is installed within a building below a critical area of the building's envelope and has a casing, which may be telescoping, and which as a window on one or both ends. An absorbent material is disposed within an interior chamber of the casing as is a moisture soluble dye that changes color upon contact with moisture and thereby changes the color of the absorbent material which color change is visible through the windows, the moisture entering the interior chamber through at least one upwardly oriented aperture on the casing. The apparatus is installed so that the window protrudes either through an interior wall section of the building's exterior wall, an exterior wall section of the wall, or both. If water penetrates the building, the water enters the casing, and causes the dye to change the color of the absorbent material to alert an occupant that a cladding failure has occurred.