Education and smart designs are the keys to success when it comes to cost-effective, code-compliant, head-of-wall construction joints.
Consider the variety of building codes that apply to head-of-wall joints. The IBC 2000 was intended to take precedence of the earlier codes and unify them into an international standard. But local government agencies may still insist compliance to earlier codes, too. So, depending on what region of the country that you operate, the UBC, the SBCCI or BOCA may also apply.
Why is all this so complicated? Head-of-wall joints are a critical link in life safety partitions in case of an emergency. Think of all the things a head-of-wall joint is expected to do: attach securely to walls, ceilings and other structures, flex with the natural movement of a high-rise building, and create a long-lasting fire-resistive barrier, even after enduring expected seismic and wind movements from mother nature. To achieve all of these functions, one must have a smart design.
The simple fact is that head-of-wall joints have traditionally been difficult to estimate, tricky and expensive to install, and often don’t perform their function well. The problem, though, is generally not with the contractor, it’s with the products and specifications they work with. This is where the education process comes into play.
Traditional double-track systems using extra long legs provide the vertical movement that the codes call for. However, they lack a true positive attachment—they are specified using longer legs and heavier gauges than necessary to compensate for the poor attachment method. This design is difficult to install, expensive and hard to inspect and ensure movement standards are achieved.
There are many ways to achieve a code-compliant head-of-wall installation. There are deep leg single tracks, some- times up to 3-inch legs—when installed with cold-rolled channels or other bridging products in the studs top knock out, this can be a code-compliant system. But, when one considers the amount of field labor involved, it’s not very cost effective. Furthermore, many times temporary screws that are installed during the assembly of the above systems get left in place, so the system in the end does not function properly or the contractor has to endure costly rework when the building inspector insists the screws be removed.
Recently, a few new clip-type systems have shown up in the market and are also code compliant. When considering these systems, beware that stud placement is predetermined by the preinstalled clip or attachment method. This can be a good thing in some installation patterns; however, in others contractors may experience costly lay out or in the field (additional) clip placement in numerous locations to positively attach the studs. This is hard to determine before hand, contractors should evaluate the type of work prior to selecting these systems.
Many contractors have found that the most cost-effective way to achieve a code-compliant, head-of-wall construction joint is to start with a slotted top track. The slots are placed every 1 inch along the length of the track leg so stud placement and positive attachment are easy. In addition to easy positive attachment, its extra-strong design is achieved by screw attachment into each stud through the tracks vertical slots, along each of the tracks legs. There are many benefits to the studs being screw attached during the construction process. For example, it prevents other trades and wind from knocking the studs out of the wall prior to the drywall being installed. This also reduces damage and rework to the framed walls.
More than just a top track, contractors should evaluate their head-of-wall system based on total installed cost, including all the assemblies’ tested and approved components, including the method of installation for a complete code compliant construction joint. The entire assembly needs to be cost effective; choice in fire-resistive building materials and various methods of construction are the keys when making the decision at fire rated construction joints.
Through education and smart design, head-of-wall construction joints can be code compliant, cost effective and trade friendly. Here are some answers to questions to help illustrate installation, inspection and specification of compliant head-of-wall assemblies.
Question & AnswerQ:Does a head-of-wall construction joint have to be a tested and laboratory (approved) listed assembly?
A:Yes, all standard building codes call for tested and approved assemblies.
Q:Does the head-of-wall fire rating have to be equal to the fire rating for the rest of the wall?
A: If the fire rating for the wall is called out to be 2 hour then the head-of-wall joint must also be 2-hour rated. 1 hour = 1hour, 3 hour = 3 hour, 4 hour = 4 hour.
Q:Who is responsible to detail the top track (head-of-wall) connection?
A: This architect or engineer of record should detail the type, size and spacing for each building type. The head-of-wall connection is most commonly accomplished with a powder-driven pin or a #8 screw.
Q:In the head-of-wall section of the various standard building codebooks, do they call for the same requirements?
A:When referencing the standard building codes (UBC, BOCA, SBCCI, IBC 2000) they do call out for the same requirements. However, they are worded slightly different.
Q:Can one use deflection track on exterior curtain walls in lieu of vertical slide clips welded 16 inches on center?
A:Exterior deflection track systems are a choice you should explore with your curtain wall designer/ engineer. Many contractors are finding this an effective way to eliminate multi-level framing that requires extra-long stud lengths and hundreds of vertical slide clips. An exterior deflection track curtain wall would frame from slab to slab with shorter (lighter) studs.
Q:Do all standard building codes require cyclical head-of-wall joints?
A: Yes, UBC, BOCA, SBCCI and IBC 2000 all reference UL 2079 (cycle, fire, hose stream) as the industry standard.
Q:What is the different between static and cyclical head-of-wall joints?
A:A static joint is a construction joint that has not been cycled [500 vertical movements ±1⁄2 inch] prior to a standard ASTM e-119 / ASTM e-814 fire and hose stream test. A cyclical joint is preconditioned by 500 vertical movements, ±1⁄2 inch, then it is subjected to fire and hose stream testing. A cyclical test criterion is UL 2079 and/or ASTM1966, which meets all current building codes.
Q:Do you have to screw attach (positive attachment) the stud to track connection at head-of-wall joints?
A: All standard building codes (UBC, BOCA, SBCCI, IBC 2000) call for a secured attachment (not to dislodge, loosen or other wise impair its ability to accommodate expected building movements). ASTM C-754 calls for attachment using screws. Positive attachment provides greater strength and use of lighter-gauge materials.
Q:Can a contractor or architect design a head-of-wall joint system using different parts and pieces of an approved / listed assembly and install it as an approved system?
A: Mixing and matching of different components is not allowed. Each head-of-wall joint must be installed as tested and approved by an approved testing facility, i.e., UL, ITS.
Q:Contractors have seen fire safing (mineral wool), structural steel fireproofing (mk-6, cafco 300) drywall, fire compounds, metal plates, and spray caulks all used for flute fill and fires stopping and many ask if these are all OK to use.
A: Many of these materials are acceptable for use in a tested and listed assembly. One may not mix assembly components.
Q:What is the most cost-effective (installed cost) head-of-wall system that complies with current
A:Spray-applied structural steel fireproof designs are being used by contractors that have the equipment to spray structural steel fireproofing many experts believe it is the most cost effective way to complete a code- compliant head-of-wall assembly. However, each company has to evaluate their own experience and equipment needs prior to evaluating a head-of-wall assembly for cost effectiveness. Be aware of each assembly’s total parts and installed cost.
Q: How does one achieve 8-inch perimeter screw pattern at the head-of-wall, when it calls for a vertical deflection condition?
A: Assemblies that have been tested and approved using UL 2079 test criteria, supercedes the 8-inch perimeter requirements at the head-of-wall.
Q:Is the head-of-wall joint in shaft wall systems required to have deflection also?
A:Most shaft wall systems are designed to deflect. However to do so, the stud and shaft liners must not be screwed to the top “J” track. Oftentimes, this is overlooked and can cause the inspector to require that the contractors to remove the screws installed in the construction joint.
Q:Can the leg of a deep leg track be snipped and bent around the leg and flange of the vertical stud?
A:Snipping and cutting track legs seriously damages the structural values of the track legs. These techniques should not be used.
Q: Why is the head-of-wall joint called the most expensive part of the wall?
A:The head-of-wall joint inch for inch is the most expensive part of the wall simply because the amount of labor it takes to build a code compliant assembly. Contractors should evaluate the installed cost of the approved systems they like.
Q: Is there a test standard for cycle, fire and hose stream test when the head-of-wall joint runs parallel to fluted metal decking?
A:Most assemblies are tested perpendicular (across the flutes) this is the most vulnerable position for the test to be performed. It is standard practice to install approved, perpendicular assemblies in all fluted deck directions. However, the design intent of the approved design must be maintained.
Q:How can one bid a project using a code-compliant system if my competition is not?
A: It is the contractor’s responsibility to install code-compliant work on the project. Three methods can be use to stay safe when bidding. 1.) Use a code-compliant system and try to be more aggressive other places in the bid. 2.) Use the least expensive system shown in the plans and specifications and offer a code-compliant system as an, add alternate. 3.) During the bidding process, write the architect an RFI and request it be distributed to all bidders to create an equal plying field. W&C