Water leakage is occurring in a building that was completed just two years ago. It is clear that not only does the building not contain any weep holes at the shelf angles and flashing, but that sealant was placed in front of the angle. Water that penetrates the masonry walls and flows down the cavity cannot leave the wall because of this sealant. We have recommended that the weep holes be installed above the flashing at 24 inches on center. However, we are concerned about damaging the flashing. Do you know of any method that can be used to install weep holes without damaging flashings?

It is difficult to add weep holes after the walls are constructed. If the weep holes are drilled, they will typically puncture the flashing. This is true even if a special guide is placed on the drill. If the hole does not go all the way through the mortar then it will be ineffective. In most cases, there are some mortar droppings at the base of the cavity. It will not be possible to drill all the way through the mortar without puncturing the flashing because in many cases the flashing forms the back surface of the mortar droppings. If the holes are not placed directly on the surface of the flashing, they will be ineffective. When weep holes are placed too high, water will not reach the weeps until it has built up on the flashing.

Another possible solution would be to attempt to remove individual bricks every 2 feet and install a weep hole along one side of the brick when the brick is replaced. This procedure will also likely damage the flashing.

Before considering adding weep holes to an existing flashing system, it is important to investigate the effectiveness of the flashing itself. Adding weep holes may actually make the water leakage problem worse. Typically, missing weep holes are not the primary cause of water leakage problems. There must also be a problem with the flashing system. When weep holes are added, water will not only leave the wall faster, but it will also enter the wall faster. Weep holes can allow considerable quantity of water to flow into the wall when it flows across the face of the wall. In this case, any defects in the flashing system will potentially be exposed to much greater quantities of water than previously. Leaks occur wherever defects are present in the flashings or where splices in flashings are not sealed watertight. If the flashings are held back from the face of the wall, water can flow off the end of the flashing and onto the wall system below.

I recommend conducting an investigation to determine why the flashing is leaking. In many cases, the only way to correct a flashing problem is to remove 3 or 4 courses of brick and to replace the flashing. The flashing must extend completely out beyond the face of the wall so that sealant can be applied between the underside of the flashing and the top of the brick below. I recommend using open head joint weeps or weep vents at 24 inches on center. It is extremely important, however, that all splice joints in the flashing be sealed watertight and any corners or jogs in the flashing be either pre-fabricated or carefully formed.