A Burning Issue
Vince Bailey / July 2017
We didn’t start the fire; no, we didn’t light it but we try to fight it.—Billy Joel
Without question, an estimator’s most dreaded foe is ambiguity. I have catalogued an entire litany of these document demons in the April 2014 installment of this column, appropriately entitled “Gotcha!” In it, I solicited the pet peeves of several bidmeisters from around the country. That piece makes it pretty clear that gotchas are legion. But one specific aspect of our framing/drywall scope seems to be particularly subject to confusion: firestopping.
Wikipedia defines a fire-stop as “a fire protection system made up of various components used to seal openings and joints in fire-resistance rated wall or floor assemblies.” That’s a pretty clear definition. However, that is also where the clarity ends. The ambiguity begins with misunderstandings as to what constitutes a rated assembly, runs through questions of where and when they are required, and ends with whose responsibility it is to provide the firestopping in the first place. The assemblies most commonly affecting the framing/drywall scope of work include fire and smoke rated walls, ceilings, shaftwall assemblies (including above-ceiling fire containment boxes or “doghouses”) and edge-of-slab fire dams.
Fire and smoke rated walls. A major bone of contention between the design team, general contractors and subcontractors, lies in the question of what constitutes a rated wall. Generally speaking, a typical one-hour rated wall on a commercial project consists of metal framing with one layer of taped, 5/8-inch drywall, floor-to-deck, on each side, with a bead of fire-resistive caulk run at each side of the head-of-wall where a gap is left between the top of the drywall and the deck for deflection. At least that is the consensus understanding of a rated wall. However, under certain conditions and/or local code requirements, some rated walls are required to have fire caulk at the top, bottom and at any dissimilar abutments. This has led some designers and/or GCs to enforce this requirement even where it is not called for. This creates another “damned if you do and damned if you don’t” scenario for drywall subs. Include the whole enchilada and you’re not competitive. Include only the consensus assembly and you’re vulnerable. Seems you just can’t win.
Then there is the case of the smoke wall. The objective of these assemblies is to block the migration of smoke from one area of a building to another. They are not fire-resistive partitions, and as such the complete sealant of the drywall on one side of the wall will suffice. Caulking materials in these cases need not be fire-resistive. Nevertheless, many designers deem the term “smoke wall” synonymous with “fire wall,” generating another lose-lose situation for the estimator.
Shaftwalls and doghouses. Whoever invented the shaftwall system should be nominated for sainthood. This ingenious “C-T” configuration of a drywall stud allows the construction of a rated wall on applications where it is only possible (or feasible) to install wallboard on one side of the partition. Duct shafts and elevator shafts are two good examples where drywall cannot practicably be applied to the non-public side. In addition, horizontal shaftwall is the ideal application where rated drywall ceilings are indicated (no, a stud-framed ceiling with two layers of drywall is not accepted as a rated ceiling). The only problem with shaftwalls lies with the difficulties that arise in finding an indication for their inclusion on many plan sets. Most often this occurs in instances where ducts penetrate a floor and either terminate or start a horizontal run, which creates the need for fire-containment boxes, or “doghouses,” as they are affectionately referred to in the trade. Two problems with doghouses: One, they are wickedly labor intensive, and two, their designation on the plans can be as elusive as a smoke-ring in a hurricane. In fact, rarely if ever will you find a doghouse actually indicated on the architectural plans. If you’re lucky, you may find an obscure note on the mechanical plans. But more often than not, you’re pretty much on your own in searching for the locations where the conditions described above occur on the mechanical plans. And woe be unto the unfortunate bidmeister who fails to include the insinuated intent of the design team.
Edge-of-slab fire dams. These mineral-wool and fire-spray strips are required at rated floor lines where a bypass exterior wall condition creates an opening at the stud cavity. Again, the problem is two-fold. Many times the damn dams don’t appear on the wall sections, or only on one “typical” section, and then only as a vague dark spot at the floor line. The other question is scope related: Is the drywall sub expected to carry it, or is the GC hiring a caulking sub?
As dire as all of this sounds, there are some good remedies to employ. One preferred course is to subcontract to a specialties contractor to perform the firestopping included in the drywall scope. The advantages are several: Since they focus only on fireproofing, they are generally certified installers and are better equipped to deal with the technicalities inherent in that scope. Moreover, they assume the risk of underbidding the work. Then too, the skill level of their field is such that they can perform the work quicker and more cheaply. Also, hiring a sub to cover part of the drywaller’s scope makes good sense when manpower is a scarce commodity.
As always, the best way to combat ambiguity in a commercial drywall estimate is to clearly state in the proposal what is and what is not included in the bid, but put an alternate number to any item not included in the base bid that may be assumed to be in the drywall scope.
Vince Bailey is an estimator/project manager working in the Phoenix area.