Published in the ECHO Journal, February 2014
Buildings are always talking to us…it just may take a “building whisperer” to hear what they are saying. Of the many things buildings do, protecting us from the environment is key. And in protecting us from rain, cold, heat and sun, the materials used in constructing buildings can wear out. While surface wear from responding to these elements is easier to evaluate, the clues to what is happening underneath the surface are sometimes harder to see. Many exterior finishes will wear and weather from age and exposure, but different clues can indicate problems below the surface.
Hidden Issues in Construction
One characteristic of many building envelope systems is that the protection from the sun and protection from water intrusion are provided by different materials, and at different parts of the system. While much of the water hitting the surface is deflected at the surface, that is often not the primary water-repellant material. Keeping water out of the building is often the chore of materials behind the surface, on the backside of the exposed finish. These materials that best repel water are hidden inside the walls, mainly because the properties that make them water resistant leave them more vulnerable to sun damage.
Exterior plaster (known as stucco) often cracks, but it is the location of those cracks that can indicate a hidden problem. Routine plaster cracks occur in the field of the walls, extend diagonally from windows or doors, or happen at changes in wall planes (surfaces). These cracks should be monitored for any changes, and repaired and sealed during routine maintenance of the building. Changes in these cracks can indicate improper attachment of the plaster, inadequate structural connections in the framing behind, or improper plaster mixing or application. These issues can result in excessive movement of the materials. Left untreated, cracking will introduce additional water to the membrane layer behind. The paper behind the plaster is meant to manage routine water, but will have a reduced useful life if exposed to extraordinary water.
Some cracking can indicate other hidden problems below the surface. Cracking on the underside of arches, or over openings, can be the result of water collecting behind the plaster at the opening or the arch. Without a proper weep molding at the arch, water within the plaster can be held inside the flat underside of an opening, swelling the wood within the wall and contributing to rotting the framing.
Anytime plaster is used on a horizontal surface, either on the topside or the underside, clues in the surface can indicate problems below. Plaster on a upward-facing horizontal surface, often known as a “potshelf”, can be source of problems. These should be monitored throughout the life of the building, as the actual waterproofing material of the potshelf is hidden below the plaster. Leaking at these surfaces can be hidden within the walls, with damage only becoming apparent after worsening over time.
Plaster on the underside of a deck or exposed surface above can give clues to issues above. Any damp areas not created by run-off from the adjacent vertical surfaces (isolated from the edges) can indicate water intrusion from a roof or deck above. Further investigation should be performed to find the source of the moisture.
It is the dual location of protection from the elements (sun and water) that makes some repairs to walls more difficult. Application of a surface coating, which may reduce water absorption of the plaster itself, often will not tie into the actual flashings and water resistant material. Without a proper transition, water will breach the applied coating at windows, doors, pipes and other penetrations and become trapped within the plaster. Typically, flashings at windows, doors and other components of the water protection system are tied into the hidden materials. Trying to tie a surface-applied repair into these hidden components often results in a failed repair. The best approach is to identify the actual breach of the water-repellant membrane, and fix the system at that layer.
Often, in older projects, plaster was continued into the ground at the base of the walls. This will not allow for the required drainage of the plaster assembly. The resulting moisture retained in the plaster can damage the building paper and cause surface damage (spalling) of the plaster. In any location, where the ground level has been allowed to creep upwards and bury the plaster and any base screed, there can be hidden damages from this water not allowed to drain from the plaster. These conditions should be investigated to determine the underlying conditions and any required repairs, and the ground conditions modified to eliminate the buried wall.
Similar issues occur at wood, hardboard and other composite material siding systems. The actual water-resistant layer usually occurs behind the siding, and similar to plaster systems, the repair must occur at and tie into the hidden water management layer. While surface flashings may deflect the bulk of rainwater, flashing transitions must occur at the hidden protection layer. The lack of continuity of these layers will contribute to continuing damages. In wood detailing, look for the management of water that may bypass the surface. Conditions where wood stacks upon itself, as with applied trim with no flashing visible, or wall top trim that may not allow for proper drainage off the wall, are susceptible to damage from this unmanaged water. Paint on these surfaces, while important to protect the wood, may not keep water out of the wall assembly.
Of most concern is where different materials and systems come together. Typically, where walls, roofing, decking, windows, doors and other components meet, there should be a transition zone, material, and detail that allows for a proper seal. Seldom do different materials naturally seal to each other. Of particular suspicion is when plaster mysteriously stops, without a trim, molding or termination flashing, at adjacent roof and deck surfaces or other components. When plaster stops flush to a deck system, or there is no trim or sealant joint at a connection to siding or roofing, there may be no transition of the hidden water resistant material behind the plaster. These conditions should be monitored, or tested, to determine how they are performing.
Walls are only one component that may conceal hidden damages. The ceiling below a deck above can reveal problems with the deck system. Stains can indicate failure of the decking system. Surface-applied deck membranes show distress more readily, and can be repaired quickly. Cracking, visible plywood decking seams or blisters in the coating will indicate a failure. Systems with hidden membranes, as with walls, don’t tell their story so clearly. Concrete topped deck systems often have a hidden membrane below the surface. If this membrane fails, it may not be apparent for some time. Often, construction of these systems resulted in a poor bond of the membrane to the perimeter flashing, resulting in leaking to the framing. Keep an eye on the adjacent surfaces, the walls and ceiling below the deck, for clues to any failures.
Roofs are typically the largest “horizontal” building systems. Steeper sloped roofs of tile or asphalt shingles are usually more reliable, as bulk water sheds off them rapidly, lessening the chances of leaking. Pay attention to the perimeter details and penetrations in these roof systems, for any discontinuity of the flashing or tie-in to the roofing material. With roofing, transitions are usually the weak point, and merit attention during annual roof inspections. Most often, routine maintenance is all that is required on steep sloped roofs, at least until the material is worn out and the useful life is reached.
Low-Slope, or “flat” roofs can have additional problems. The less water directed off the surface quickly, the greater the chance for failure. At low-slope roof systems, pay attention to the edge conditions, penetrations, changes in slope, and any valleys or crickets that direct water to the drains. There are several issues that may be visible, including blisters or open seams, and delamination from perimeter flashings, which can indicate water intrusion. Also be aware of any soft spots in the surface, which can occur over damaged sheathing below the roofing. As with wall systems, if the roofing meets an adjacent wall or other surface without a transition detail or material, it may indicate a lack of continuity with the adjacent hidden water resistant materials.
A further concern with “hidden systems” is that often these systems, if not visible, are not required to be included for eventual repair or replacement in a mandated reserve study. Even if not included in the funding plan, these systems do have a useful life, and may eventually need attention. Reserve study inspections may not suggest funding for what appear to be permanent components of the building. Examples include the waterproofing membrane in concrete topped decks, or below-slab or concealed plumbing systems. Some plumbing systems can prematurely deteriorate due to poor pipe joint installation during construction, excessive water velocity during operation, or the pipe interaction with corrosive soils when below grade.
Similarly, reserve amounts for replacement of one system may not account for a failure of an adjacent system, which may require related work. The price of routine painting will not include repair of rotted wood or trim due to fundamental failure of a detail of installation.
Investigation of these systems, and the project overall beyond what may be the mandated minimum, can prevent funding shortcomings and allow for proper project maintenance.
By David Kuivanen, AIA.