During the construction-administration (CA) phase, the design team is charged with helping the general contractor (GC) build the project in conformance with the contract drawings and specs. Success in the CA phase comes from collaboration between the owner, design team and GC, and it requires three basic management tools: Q&A, QC and site visits.
Q&A is where the design team provides clarification to the GC’s requests for information (RFIs) about the project drawings and specifications. QC (quality control) is review of the GC’s product cutsheets, samples and proposed substitution requests for compliance with the specifications. And site visits are for reviewing work-in-place for contract and code compliance, as well as for resolving construction issues that are best discussed in the field and in person.
With the project design team’s architect typically conducting site inspections once or twice a month, and with construction always moving briskly, the architect is unable to catch every code nonconformity. With my own data center field notes as a guide, however, this article centers on what I’ve found to be the most often missed building-code items for the basic areas of building shell, tenant improvements and life safety; these mishaps surface time and again.
The Building Shell
During most walk-throughs, I seldom see many code violations for the building shell, but for infractions I do find, the two most common are thermal insulation at exterior walls and flashing at exterior-wall openings. In the former case, the most common misstep is batt insulation. The two types of insulation that I’ve seen most often in data centers are FSK-faced (foil-scrim-kraft) and foil-faced. A third type (perhaps never used in data centers) is kraft-faced batt insulation, which gets its vapor-retarding quality because its kraft-paper lining is saturated with asphalt. If untreated, however, the lining is flammable and toxic when burned.
In researching batt insulation’s Class A Flame Spread Index (FSI) of 0–25 and the smoke-developed index (SDI) of 0–450 (required in buildings designated as noncombustible construction), I’ve yet to come across an FSK-faced insulation that has an FSI above 25. I’ve found some foil-faced insulation above 25 and some 25 and under, but I’ve yet to find a kraft-faced insulation as low as 25. So, the FSI and SDI of all insulation must be checked, and those with a high value for either one must be covered in drywall to protect them. Furthermore, since FSK- and foil-faced insulation are almost always exposed when installed in mechanical or utility spaces (or when temporarily insulating the inside face of large mechanical louvers), their FSI and SDI designations should be double-checked for code compliance before installation.
The second most common misstep occurs when FSK- or foil-faced insulation is placed along the interior face of the exterior walls—which takes place during the building envelope’s construction to pass shell inspection—and when the electric-cable trays (heading inward from the outside generators) and the large exhaust fans are installed during the tenant improvements phase: large areas of the exterior walls’ insulation are removed but seldom replaced. The result is large insulation gaps around the cable trays and exhaust fans, enabling exterior heat to transfer inward owing to thermal bridging, which can cause condensation to form.
A third misstep, which rarely occurs, is when two vapor retarders or barriers are at the same exterior wall. It can happen when installing a double layer of FSK- or foil-faced insulation to double the R-value or when placing foil-faced vapor retarder on the inside of the exterior wall with a vapor barrier directed toward the exterior face of the exterior wall. Using a double vapor retarder or barrier will trap moisture between the layers, causing condensation and mold to form.
One solution to prevent all three of these insulation breaches is for the project architect to design the exterior walls as precast concrete panels with rigid insulation sandwiched in each one.
Regarding the violations for flashing at exterior-wall openings (windows, doors and especially the data center’s giant mechanical louvers), the most common mistakes are when the flashing is improperly installed or completely missing. Headers and sills at exterior-wall openings need flashing to stop rainwater from penetrating inward and to direct it outward. Without it, water will inevitably work its way into the building. Additionally, when head and sill flashings are installed, their ends are all too often not folded up to form “end dams”; and so, except for caulk that will break down over time, there’s little to prevent heavy rainfall from being channeled over the ends of the flashing and down into the wall cavity or onto interior finishes. Rusting steel headers and wet walls are clear indications of buildings with missing or improper flashing.
The most common violations in data center tenant improvements are for minimum distances to, around or under fixtures and equipment. The International Building Code requires that the clear height of protruding objects at walking surfaces be at least 80" above finish floor (a.f.f.). During site walks, however, I often come across mechanical, electrical or plumbing equipment that doesn’t conform to this requirement. And regarding service access to any adjacent mechanical equipment, I have yet to find an exception to this rule in the International Mechanical Code.
In my experience, the five most common nonconforming-height occurrences are when (1) horizontal sprinkler mains along a defined but open circulation path are below the required head height, so access to areas alongside the sprinkler main is hindered; (2) the steel frames that define a clear circulation path below giant mechanical ducts are too low, so access from the circulation path to the adjacent equipment aisles is hindered; (3) the hanging climate sensors (residing at various heights along circulation paths to monitor the environment of sensitive data servers) are at times as low as eye level; (4) the bottom end of dozens of thick, lateral ground wires (awaiting connection to the as-yet uninstalled servers) hang below the required 80" a.f.f., especially when their clipped, serrated ends are dangling as low as eye level; and (5) the bottom of the large, 20"-diameter insulated mechanical ducts coming from the generator yard into the building are too low.
Although the clearances I’ve discussed so far have been for minimum height, many minimum horizontal-distance requirements tend to be missed as well. The most common violation occurs when computer-room air-handler units (CRAHs) are on a raised-floor system. Here, the CRAHs typically sit along the data hall’s perimeter (with rows of server racks occupying the center areas)—but raised-floor tiles are always absent from the 4"–8" gaps between adjacent CRAHs. Because a typical raised floor has at least a 30" drop to its supporting concrete slab, any gap between adjacent CRAHs that’s 4" or wider requires floor tiles or a guard rail. An easy way to avoid this violation is to simply set the CRAHs closer together.
Other common code violations occur when (1) the rooftop mechanical’s dunnage platform is 30" or more above the roof but is missing the requisite stairs and guardrails, (2) the systems furniture is delivered but the local fire marshal wants to have all its electrical devices preinstalled, and (3) plumbing vent pipes aren’t sloped toward the drain pipe they serve, thereby trapping water and possibly forming mold or cutting off airflow.
Lastly, and not surprisingly, the most widely overlooked clearances in data center tenant improvements are for the requirements in the Americans with Disabilities Act (as defined by the 2010 ADA Standards for Accessible Design). But since these violations are numerous, I’ll address them in a future article.
Beyond violations to ADA requirements, most code violations regarding construction materials and equipment tend to involve life safety—which is unfortunate, since the most important issues seem to be coupled with most frequent errors. The following are common construction-material violations:
- Fire-rated walls not being continuous from rated floor to rated floor/ceiling assembly
- Fire-rated walls that end at the underside of a concrete floor above, but the wall-to-ceiling joint isn’t sealed against smoke penetration
- Fire barriers that contain hidden breaches (such as holes above an acoustic ceiling or below a raised floor)
- Access panels in fire barriers that aren’t fire rated or simply unclosed
- Concealed fire-barrier spaces (in attic, above ceiling or under floor) that lack 3" tall stencils designating them as fire rated
- Penetrations into fire barriers that aren’t installed per an approved tested penetration-firestopping system
- Firestop pillows without fire caulk filling the air gaps between them
- Nonrated control joints in fire-rated walls
- Nonrated fire-extinguisher cabinets recessed into fire-rated walls
- Combustible construction materials in a data center’s typically Type II-B noncombustible construction (with the most common examples being temporary walls that use plywood sheets and wood framing, plywood equipment-mounting boards in electric rooms, and rooftop mechanical platforms)
- Temporary walls (during construction) lacking the necessary fire rating for wall or passage doors
- Temporary passage doors creating a potentially dead-end fire-rated corridor when they don’t have a panic exit device, or they don’t swing in the direction of egress travel
- Means-of-egress doors in rated corridors or to an exterior right-of-way are temporarily locked or blocked off without a second means of egress
Below are frequent equipment violations:
- Electric feeders in a plenum not being contained in a conduit, or the conduit in a plenum being made of PVC or other combustible materials
- Fire-barrier putty packs not installed in back-to-back electric outlets (within 12" of each other), or too many adjacent electric outlets (five outlets maximum in a 10-square-foot area) without putty packs
- Smoke detectors located more than 12" from the ceiling
- Fire-department connections not being visible at all times
- Knox boxes not located outside fire-control rooms
- Orange-colored plastic covers still on sprinkler heads and smoke sensors (factory installed and maintained during most of construction for damage and dust control) at final inspection
- Sprinkler heads’ white plastic cover plates set flush to a drywall ceiling, rather than a quarter inch below it to prevent the covers from inadvertently being painted over and “glued” in place
- Extra sprinkler heads or any special sprinkler-installation tools not placed into attic stock
- Halotron fire extinguishers sized at 11 lbs when they must be at least 15 lbs
Although the aforementioned common code violations should be avoided, they certainly shouldn’t be repeated from building to building. So, the project architects, engineers and consultants should double-check their drawings and specs for violations before permitting, and the project’s general contractors and tradesmen should be checking for violations all throughout the construction progress. And all entities, armed with a prewritten codes-review checklist, should together conduct one last codes check during each phase’s final punch walk.
Leading article image courtesy of U.S. Air Force/Sara Vidoni
About the Author
Dean Ventola, RA, NCARB, LEED AP BD+C, is the Director of Construction Administration at DVA Architects in Gaithersburg, MD, a nationally prominent mission-critical data center architect.