News and Articles

In the last issue of our newsletter we addressed the importance of properly installed vapor barriers in the wall assembly of a building.  A second defense against moisture penetration, and not to be overlooked, is through-wall flashing.  Neglecting this critical component can render the vapor barrier ineffective, resulting in hard-to-find leaks and costly repairs.

Through-wall flashing consists of a durable, water-proof membrane that collects water, much like a gutter, that has permeated the exterior building façade and facilitates drainage back out again.  This is an essential element of the wall assembly, especially where brick has been used.  Brick, although favored for its durability and aesthetic value, is porous and will permit water migration, especially at the mortar joints.

Properly installed flashing, in combination with a vapor barrier, stops water from traveling through to the interior of the wall.  Through-wall flashing at grade level also helps prevent water from rising into the upper portion of wall from the foundation masonry.  Today’s building codes require that flashing be placed above the heads of windows and doors, at window sills and at roof lines, particularly where the roof line of one building wing meets the wall of a taller wing. It’s worth noting that this last item is sometimes overlooked during a roof replacement or renovation. 

Property owners or managers should take steps to ensure that the restoration contractor is able to review the existing building plans.  If plans are not available, through-wall flashing in masonry construction is identifiable by weep holes, but the presence of weep holes does not necessarily mean that through-wall flashing was installed during construction.  Weep holes are always installed on top of the flashing at doors and windows, as well as at the bottom of the wall, enabling drainage and ventilation of the air space within the wall assembly.  Weep holes are crucial to a properly functioning wall assembly and should always remain unobstructed.  The unintentional caulking over of weep holes, debris accumulation or the mere absence of weep holes during construction, restoration, or repair can lead to other moisture problems down the road.

Repairing structural damage or replacing improper flashing can be time consuming and expensive.  It’s always best to use materials that are going to last the life of the building, such as copper, stainless steel, terne coats, or the preferred Ethylene membranes.  Aluminum should not be used.

A trained professional can inspect and identify a building for signs that a wall assembly may not be performing according to standard and offer the best course of action for correction.  A thorough inspection of the building should be done by a qualified technician, before undertaking any work, to ensure that repairs are effective and permanent.