When it comes to a building’s expected lifespan, it is always important to regularly maintain the building envelope to help prevent water infiltration and unsafe conditions. Deficiencies in the building envelope present themselves in many forms, from open roof seams, to large cracks in the masonry. The limited life span of building materials, combined with the effects of freeze/thaw cycles over time, will eventually result in these visible deleterious conditions. These issues can often be resolved by performing general exterior repairs. In some cases, however, deficiencies in the building envelope such as bulging parapets or sagging roof decks might be symptomatic of problems that lie beneath the surface.
In most types of masonry construction, steel framing acts as the building’s skeleton. Like the building’s skin, the façade and roof membrane system protect the underlying structure and interior spaces. After long periods of water infiltration, underlying steel framing can deteriorate and cause cracks or bulges in the facade. When steel undergoes oxidation (rust accumulation), extensive deterioration may cause delamination of the steel at the flanges and webs of the beams. Delamination is a separation of metal into layers. Over time, the beams will expand, and the oxidized material will flake off, resulting in section loss (missing metal) in the structural members.
It’s difficult to tell whether a facade condition is related to an underlying structural issue when performing just a cursory visual inspection. In an attempt to avoid more invasive investigation techniques however, facade engineers use different methods to identify the cause of deficiencies before recommending repairs. Sometimes the age or type of building will indicate the underlying building structure. This information may allow a building envelope inspector to hypothesize as to what underlying conditions are most likely the root cause of the façade deficiencies without the need for more invasive testing, or at the very least, eliminate possible conditions. For example, if all of the shelf angles on a building have severe rust accumulation, the mortar at each floor can be systematically displaced from the joints, indicating a systemic chain failure from rust jacking rather than an isolated mortar issue. Furthermore, if the steel is rust jacking, it means moisture intrusion within the wall system has deteriorated primary elements of the exterior structure and the degree of failure may increase more rapidly. This can cause a chain effect, from the expansion of steel to mortar cracking, allowing moisture to reach other steel anchors, cracking masonry units and so on.In this situation one can visually determine that the shelf angles must be refurbished or replaced. Unfortunately, it’s sometimes impossible to determine whether visible deficiencies are isolated to the facade or how an underlying condition may be causing them. In these cases, probes to open areas of the walls must be performed. If issues with a building’s structural framing are observed, they should be evaluated by a structural engineer. Sometimes the deteriorated conditions in the structural framing may require repairs to reinforce the structure. Since there are several steps involved in performing structural repairs, the duration of a facade project is usually extended.
Structural issues can also present themselves during roof replacement projects. Unaddressed water infiltration into a roof membrane can cause damage to the roof joists, metal decking, and spandrel beams. Whether it’s mold and bacteria eating away at moist wooden roof joists, or corrosion weakening metal components, water is the most common cause of damage to structural members. It is important to make sure there are proper flashings around the roof perimeter and penetrations and that drains, scuppers, and gutters are kept clear to prevent ponding water. If standing water is observed more than 24 hours after the last rain fall, the roof drainage system is likely insufficient and should be inspected by a professional. As with facades, it’s often difficult to predict or assess the condition of the underlying roof deck and the supporting roof structure until the deck is opened. Roof probes should be performed on old or highly deteriorated roofs to properly identify any potential structural issues before designs for replacement systems are finalized.
As of July 1, 2019, all structural work, even in the context of a building envelope project, must now be filed under a separate work permit. This means that a completely independent set of drawings and DOB filing forms must be submitted. Furthermore, filing is now a completely online process. Similar to FISP reporting guidelines, property managers and building owners must establish a DOB Build Now account in order to sign related filing paperwork.
Besides filing for and obtaining the proper permits, building owners or managers should be aware that the general or restoration contractor working at their building may not be qualified to perform structural repairs. A separate contractor or a sub-contractor may need to be retained in order to perform this type of work. Additionally, the building envelope engineer on the project often doesn’t design structural repairs; therefore, a structural engineer may also need to be retained.
Lastly, structural repair work requires special inspections. Special inspections must be performed by a licensed third-party special inspector hired by the owner. The special inspection report must be submitted to the DOB in order to close out the job.
When it comes to building maintenance, it’s imperative to protect the underlying structure from damage that is costly to repair. We also recommend that probes be performed during the design process. This can help avoid unforeseen conditions during construction that can sabotage project timelines, incur additional mobilization expenditures, result in design delays and lead to unexpected structural repair costs.