As any veteran developer or builder knows, the consequences of a poorly constructed apartment building can be devastating, in both the short and long terms. That's why quality assurance in construction is essential.

Based on analyses performed by my company, Irvine, Calif.–based LJP Construction Services, which has served hundreds of projects nationwide, problems with build quality stem from deviations of three key types: deviations from (1) approved architectural plans; (2) approved manufacturer-recommended materials; and (3) standard field-quality practices. Labor shortages and lack of adequate trade contractor training are also contributing factors.

Each of these factors varies in severity across the many different U.S. housing markets. They also vary with respect to building type and building assembly.

Here we explore the “seven deadly sins” of multifamily construction, which can be avoided through the application of building science principles and a commitment to fixing problems prior to building completion.

In a tight labor market, some construction teams might take shortcuts in the field. At LJP, we've seen connection hardware replaced with products that haven't been tested, certified, or agency approved—a change that can affect the structural integrity of bearing walls. We've also seen beams installed upside down, undersized headers, joist hangers improperly secured with the wrong nails, shear panels with edge nailing too widely spaced, and load paths compromised.

Improperly constructed components may increase the likelihood of damage down the line. Quality problems can happen when assemblies are haphazardly constructed due to material deficiencies, labor issues, or tight construction schedules. Fortunately, most multifamily housing projects are designed by experienced architects and structural engineers who closely follow professional standards of practice and building codes, and critical assemblies are inspected by a combination of local government building officials and third-party quality assurance (QA) companies.

Water leakage from any source can result in mold growth and unhealthy living conditions, drywall damage, and interior structural damage. A lack of understanding about the physics of moisture movement through roofing and wall assemblies can lead to destructive results, including water blisters forming under roofing membranes, causing delamination and rotting of the roofing substrates and wall assemblies. This is due to moisture driven by thermodynamic forces acting on the building. To fix this problem and avoid premature building failures, home builders are increasingly designing and constructing homes with four protective building-envelope layers to control (1) bulk water, (2) air leakage, (3) vapor movement, and (4) thermal performance.

Defects in windows and doors are often the first to be noticed because water intrusion will leave telltale interior drywall stains. The causes of improperly installed windows and doors include improperly lapped flashing membranes; damaged sheet-metal head flashing (hairline cracks in soldered joints); and reversed flashing at window heads, jambs, and sills. Deeply recessed windows are particularly troublesome if lacking positive sloping sills for effective drainage.

We once heard of an installing subcontractor who mis-lapped a radius-top window flange by ¼ inch, causing interior water leaks cascading down the interior living room wall of a condominium. This generated a $2 million lawsuit (settled out of court for $400,000). Preventive actions to keep the problem from occurring would have included proper trade training on mock-up window assemblies, water penetration spray testing (following ASTM protocols), and responsible field supervision combined with independent third-party QA oversight.

Brick, rock, aluminum, wood, fiber cement, vinyl, stucco, and EIFS are typical exterior cladding systems that both protect the building structure and provide aesthetic appeal. But improperly installed cladding without close attention to material transitions and exterior penetrations can lead to significant water-intrusion problems. Without the four control layers identified above, mold growth and deterioration can happen very quickly. Failures in the exterior siding will lead to the removal of the assembly to identify the sources of entry—always difficult to isolate and eliminate.

Also, chemically incompatible sealants and flashing membranes at transitions along building elevations and at window and door locations can cause each other to melt, creating a black goo oozing out onto the exterior cladding surfaces. Homeowners experiencing these conditions just a few years after closing are easy targets for attorneys offering free inspections and tend to sign up for a “no cost” lawsuit against the builder.

Mechanical, electrical, and plumbing (MEP) systems are somewhat less prone to deficiencies because they're generally installed by professionals who are trained, tested, and licensed in the trade. Nonetheless, defects can occur in electrical wiring and plumbing, and, because these systems are hidden behind walls and ceilings, they can be difficult to find and correct.

We've seen dryer vents plumbed into crawl spaces and attics, forcing hot humid air into relatively colder cavities where the moisture condenses and creates mold growth, leading to rotted framing. Missing nail plates will allow nail penetrations into cross-linked polyethylene (PEX), CPVC, and copper water supply lines. In one case we encountered, the sewer drain line was punctured, allowing black water (raw sewage) to leak into the wall cavity.

Poorly installed insulation creates gaps in the thermal control layer, leading to comfort and performance issues in the home. Fortunately, more installing trades are learning about the thermodynamic basics of insulated wall systems and becoming better trained in the installation process. Equally important, the industry is moving toward exterior rigid-insulation systems to reduce thermal bridging from exposed framing members. We expect this solution will be one of the necessary elements adopted to meet net zero energy conservation goals in certain climate zones.

A building's structural integrity can be compromised by corrosion of the reinforcing hardware in concrete, such as rebar, post tension cables, and connective steel straps. This stems from improper mixing of the concrete (for example, using too much water), resulting in highly porous concrete. Law firms have, in the past, won millions in settlement dollars through jury and nonjury trials in such cases. Fortunately, most builders today are specifying Type V, sulfate-resistant concrete, with low water: cement ratios of 0.5 or 0.45, where the soluble sulfate soil conditions are moderate to extreme. If the architectural plan details aren't coordinated with the geotechnical report recommendations, verifying that the project designs and specs conform with the underlying soil conditions, problems can arise.

Safety is a critical issue in balcony design and construction—whether it involve a two-story single-family home or a four-story wood-frame condominium building. In all cases, design details should include a step-by-step installation sequence for complex flashing assemblies, such as saddle-flashing of cantilevered structural supports and proper integration of deck waterproofing membranes with the through-wall scuppers on enclosed balconies, as well as the roof-to-wall and balcony-to-wall intersections. We've observed balcony assemblies constructed with reverse slopes, which concentrates the water at the deck-to-wall interface rather than away from the vertical plane of the exterior building wall. Such oversights can result in rotting structural members, leading to catastrophic failures.

Take care to avoid these seven deadly sins. Your developments will be the better for it.