Roof Coping Problems vs Wall Problems: How to Identify and Solve Them
In today’s blog, here on our website, we’re going to take a look at a particular case study where there is masonry damage caused by water infiltration. The wall that we’re looking at is built with a relatively modern brick. Most of the bricks buildings here in Washington DC are built with historic bricks that are similar in most ways but I have a couple key differences in permeability and compressive strength resistance. Also, generally, historic bricks will be assembled into partitions in walls with a moderately or comparatively high permeability lime mortar. This lime mortar also has a lower compressive strength, intentionally.
The big difference though is that the historic elements are generally more permeable. Nonetheless, even with a higher degree of permeability, these walls should not be highly affected by regular water entry from normal or typical weather patterns, except the typical wear over many decades which is natural.
Often though, we get called by some clients who initially started the repair process by looking for a masonry contractor and then later realize that the problem is actually coming from the roof, not the exterior brick masonry wall. In this particular case, there is leakage coming through the roof system from an area near the parapet. The parapet is a portion of a wall which extends above the area of a low slope roof. Most Washington DC buildings have at least one or two walls of parapets that extend above the low slope or flat roof of the building.
In both the picture above and the picture below, you can see lines like white streaks running down the wall. This is a salt deposit called efflorescence that happens in masonry where there is excessive moisture. This type of phenomenon of salt deposits on the surface of the masonry specifically happens where there is water or hydration that enters one part of the wall and then saturates the interior (or exterior) part and leeches towards the outside (or inside), across the span of the wall assembly. When the water reaches the opposite (or adjacent) surface of the masonry, it evaporates but it leaves these salt deposits behind in a crystalline form.
If you look closely in these pictures, you can see that the moisture points that show up indoors start almost near the top of the wall. This particular roof system is a large span commercial roof with a steel truss framing system. Although the steel truss is relatively tall, you can see straight through it around the web that connects to the top and bottom chords of the truss. You can see that the light white color of the efflorescence is apparent or visible all the way up near the top, behind the top chord of the trust.
When the efflorescence comes in or is visible that high on the wall, It generally means that the water is entering relatively high in the wall. Rising damp is a phenomenon where masonry will wick water upwards, but it’s very unlikely for this type of efflorescence to be caused from rising deep at the foundation. Instead, in this case, it’s much more likely that the water entry is actually happening at the roof. By comparison to water entry from a roof, rising damp type moisture or water damage will often cause significant damage at the base of the wall before it even begins to show signs of damage at the upper or even middle portions of a exterior wall.
When you look closer at the efflorescence at the side of the brick wall, you can see that the water which has deposited this salt like material has left a ripple type shape, the same way you would see in discoloration on paperwork that has gotten wet, for example. At this point, although the area of the damage is relatively extensive, the damage itself is not yet debilitating or severely damaging to the wall. The damage is light and superficial at this point. If left unmitigated, if the roof is not soon repaired, damage will continue though and the wall will, over time, begin to lose the cohesive binder materials which hold the wall together.
In some cases, water entry like this could also emanate from the exterior side of the wall, but in this particular case, as shown in the pictures below, we can see the exterior side of the wall has very little visible signs of observable damage to the masonry or the mortar.
We recommend every building owner in DC who values the longevity of their roof (and their investments) and building use a contractor who values the simple and important principles of proper roof construction like Dupont Roofing DC. Learn more about our company and the proper techniques of working with roofing on historic buildings in Washington DC here on our blog at DupontRoofingDC.com, and you can call us at (202) 840-8698 and email us at dupontroofingdc@gmail.com.
