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June 28, 2012

Mixed-use construction becomes a science

  • The contracting industry has seen big changes over the last 25 years in the systems, materials, details and codes for mixed-use construction.
  • By KEN COLEMAN
    Compass Construction

    mug
    Coleman

    Who says you can’t teach old dogs new tricks?

    Over the last 25 years, the evolution in the systems, materials, details and codes for mixed-use construction have been tremendous.

    In the very early years of mixed-use apartment construction, a dog and a pickup truck were practically the extent of general conditions. Construction documents were typically “permit ready” and most issues were expected to be resolved in the field. Schedule trumped quality control and subcontractors considered safety a necessary evil.

    Thank goodness times have changed.

    Mixed-use construction has matured to a place of serious management and detail. The old dogs have been replaced with collaborative pre-construction, in-depth knowledge of system assemblies, and focused quality control.

    Mixed-use construction is a combination of shell-and-core and tenant improvements all at the same time.

    Having started in commercial construction, I have gained respect for the complexity of assembling this product type. It requires a leaner group of subcontractors, using systems that can’t afford to be over engineered and proformas that are pencil line thin and have little margin for surprises or “extra credit.”

    Because of the new complexities in the world of mixed-use construction, contractors are required to treat it as a science.

    Mixed-use projects are a hot product and there are many who want to get in on the action. As I have experienced the growth of mixed-use construction over the years, the following is a sampling of my lessons learned, or “new tricks.”

    End starts at the beginning


    A zero lot line apartment
    comes together
    Compass Construction crews pre-wrap the wall panels at Harbor Urban’s Nova apartments in West Seattle.

    A worker applies sealant for a panel seat.

    Nova butts up to a CMU building.

    Workers stand and join panels.


    Pre-construction is everything. In the past, mixed-use development sites had fewer constraints and contractor input was extra credit. Now, early contractor involvement with the design team is critical for mixed-use construction.

    Early pre-construction is not a new concept, but in mixed-use projects the tight in-fill sites are more problematic with logistics, utility access and neighborhood conditions. The following are a few examples of what pre-construction should include:

    • Building on zero lot lines against neighboring structures with air infiltration and waterproofing requirements is a collaboration of code, design and constructability issues. The mixed-use systems have to be customized to neighboring building assemblies. Creating a zero lot line detail against a neighbor’s concrete wall is very different from building against a corrugated metal wall panel.

    The use of wood-frame construction makes this even more of a challenge. Often underpinning is required and shoring/access easements must be obtained.

    These challenges can be overcome with early planning and team collaboration.

    • Site logistics including the location of the crane (typically smaller, self-erecting cranes) in relation to power lines, hoisting access and over swing restraints can be a challenge and need to be included in the contract documents. The surcharge of self-erecting cranes can impact the shoring design, and tower crane footings need to be designed around storm drain systems and footings.

    • Early and continuous review of design documents by the contractor saves the owner time and money and gets the project on the radar of the subcontractors.

    Firsthand knowledge of what works and does not work in the field needs to be integrated early in the design. As new products are introduced, constructability issues must be vetted (especially before commitments are made during the permit design-review process). Thorough red-lining by the contractor as the documents develop is essential. This process exposes conflicts, discrepancies and missing information; and should reduce the volume of future field questions.

    Design-build mechanical, electrical, fire sprinkler and plumbing work is typical to this type of construction. It is required to secure that team early to aid the other design team members. This should include generating construction documents for the other subcontractors to reference prior to the compilation of the final construction budget.

    Think like raindrop

    The new concept of managing water intrusion in mixed-use projects has taken more of a Zen-like approach. In the old days, the expectation was the exterior envelop was the only line of defense. It was a rigid, single-minded expectation of no intrusion allowed. Now the approach is to have a backup plan for the exterior skin.

    The “rain-screen” backup plan acknowledges that water may penetrate the exterior skin and allows it an easy path out with vapor/water barriers and flashing systems. This concept works for types I, III and V construction.

    Wood-frame construction has probably benefited the most from this concept. Designers have acknowledged wood-frame construction moves, shrinks and flexes, so the skin protection must be “flexible” in its approach to waterproofing.

    Water must be kept out of wood-frame construction. If that’s the case, wood-frame construction can be durable and provides a great thermal and seismic structure with a price point that is tough to beat, especially in the Pacific Northwest.

    Quality is job No. 1

    I hate to say this, but litigation has been a good thing for the quality control of mixed-use housing. Originally when projects “self-ventilated,” water intrusion and detailing were not as critical. As projects became air-tight for energy efficiency, leaks became fatal. Mold became the new four-letter word.

    Thermal and noise considerations were just that — considerations. Little attention was paid to ensuring the quality of these details as an industry standard.

    The good news is technology and materials have caught up with expectations for quality. Instigating punch lists through the course of construction is required for a long-term successful project. Mock-ups for assemblies have become an industry standard. Demanding quality from subcontractors, providing the staff to monitor the construction, and using tested QC check lists are a few of the tools for success.

    As the expectations of renters increased, and owners understood the impact of this on their bottom lines, owners turned up the heat for quality and the industry caught on and improved.

    Everyone goes home

    In the early years, many subcontractors considered hard hats as optional accessories. Sometimes siding was installed with boson chairs (Spiderman would have been proud). Safety harnesses were worn, but not attached to secure points.

    Perhaps my memory has exaggerated reality, but basically, safety was not as important as it should have been.

    Fortunately, safety is now a top priority. L&I has done its job. Projects are safer and sites are better organized, professional looking and cleaner. Safety not only creates a better working environment but creates pride in the project. Subcontractors get it now and obtaining compliance is not a painful process.

    New tricks

    Old dogs can learn new tricks: Mixed-use construction has proven that. Providing quality and affordable market-rate housing is essential if we are to meet the future housing needs for Seattle. Fortunately the mixed-use construction industry has evolved to a place that makes it ready to accept that immediate challenge.


    Ken Coleman is a native Seattleite with an architectural degree from the University of Washington. He is owner and president of Compass Construction, specializing in mixed-use housing.


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