How to waterproof in-floor door operators

by arslan_ahmed | September 29, 2023 4:00 pm

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By Daniel Gibbons and Matthew Worster

Designers of exterior facades commonly locate door operators in buildings on door heads in entrances that are not all glass. Head-mounted door operators function in a sheltered environment, typically on the wall’s interior side, and are relatively easy to access and maintain.

However, head-mounted door operators are starkly visible in an all-glass facade, and though all-glass facades are still commonly used, the unsightly aesthetic motivates designers to look for another location. When budgets and surrounding floor systems allow, designers are increasingly favoring in-floor door operators. Visually hiding door operators under thresholds is a popular trend, as well as a strategy to realize the designer’s vision of an all-glass building entrance.

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Connecting and integrating waterproofing to entrances/exits

Where entrances are over occupied space, the installation requires waterproofing. A common example is exiting a building onto a landscaped terrace that is over a parking garage. Figure 1 shows an example of this instance under construction. The photographer is standing on the terrace. The raised slab with the first panel of glass will soon be interior space. The terrace waterproofing will turn up the raised slab, but one can see the two large block-outs (arrows) that will accommodate the door closers.

The in-floor door operators at the edge of the terrace waterproofing will span the division from interior space to exterior. Located in the waterproofing termination, the in-floor operator anchorage and power supply must integrate with the terrace waterproofing. Stand-alone buildings without below-grade terraces have similar issues. The foundation waterproofing often terminates at grade. The in-floor operator of an exterior door is typically recessed into the slab edge at the foundation waterproofing termination, creating a similar condition to Figure 1.

Connecting waterproofing to storefront entrances is already a challenge, as most designs try to straddle the exterior-to-interior transition at the base of the wall with upturned waterproofing, a threshold pan flashing, and a threshold plate. Inserting an in-floor door operator, with its motorized rotating spindle and conduits for power, into the waterproofing interface increases the degree of difficulty, given tight and small spaces involved and the need to seal all penetrations made in the waterproofing to anchor, drain, and power the closer long-term watertight.

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One option to protect the door and the threshold includes adding a canopy over the door. The canopy should broadly deflect water away from the door, the gaps around it, the threshold, and the jamb intersections. Canopies that are large compared to the height of the door can be effective, assuming they extend far enough to shelter the door, threshold, and exterior edge of the operator. In contrast, more modest canopies or designs with no canopies fail to protect doors and thresholds from wind-driven rain. If there is no canopy or a shallow canopy, wind-driven rain can strike the wall above the door, ultimately washing over the door and its threshold. Therefore, protecting the waterproofing at the threshold is vital.

Terminating waterproofing at doors with in-floor operators

Some designs try to keep all the waterproofing on the exterior edge of the operator, but the operator typically extends into the exterior space beyond the door. Terminating upturned waterproofing outside the building wall is an ill-advised practice without extensive precautions. Continuing waterproofing under the operator requires designing, installing multiple penetration details, and providing conditions that allow the operator to function by rotating a heavy glass door. Running waterproofing under the door operator is the better strategy, but the designer must first understand the operator and its requirements.

How in-floor door operators work

To effectively waterproof a threshold with an in-floor door operator, one must first understand how a door operator works. An in-floor door operator consists
of an electric motor that rotates a vertical axle at the hinge side of a door. The axle rotates when triggered by a switch or small opening force applied to the door. The bottom of the axle usually terminates within the operator’s housing, but some designs allow it to extend through the bottom of the housing. If the waterproofing is directly under the housing, wrapping waterproofing around a rotating axle is difficult, if not impossible.

Large doors require robust operator housing and electric motors not only to operate the door, but also to hold it in place when it is not operating. Operator design considers the use frequency and factors in weather exposure and wind resistance to prevent slamming. To open the door, the motor quickly applies torque to the door axle. An all-glass, full-size entrance door can weigh on the order of 453 kg (1,000 lbf). When the motor applies torque, the motor and housing need to react against a rigid anchor. Soft surroundings, such as thick waterproofing membranes or unintentionally flexible anchorages, cannot provide the rigidity these operator anchorages require.

As door operators are electrically powered, wiring is necessary. The waterproofing strategy discussed ahead involves putting the operator above the waterproofing. However, electrical power must penetrate the waterproofing to reach an operator above it.

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In terms of the door operator itself, some manufacturers describe their products as “exterior rated,” but beware of this term, as it does not necessarily equate to “waterproof.” “Exterior-rated” often means the device can operate in exterior exposure. However, the device may be riddled with holes for wires and anchorages. The device may be appropriate for exterior use, but if water can flow through the product, it certainly is not “waterproof.”

Waterproofing door operators

Operating the door or keeping the door secure against wind creates a significant load that must transfer from the door, through the floor operator assembly, and into the structure to keep the operator and door stable in service. The waterproofing system typically crosses this load transfer path. If the waterproofing, door, and structural design are not coordinated
well in advance, the waterproofing will most likely be compromised.

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Typically, door operator manufacturers are silent on the exact methodology of how the operator attaches to the structure. Product drawings often show holes or slots in the perimeter of the operator housing to accommodate securement,
but most manufacturers decline to take on the responsibility of designing
the anchorage itself. Manufacturer’s shop drawings often simply state “ANCHORAGE BY OTHERS,” leaving the responsibility to project designers or installers. Where plaza waterproofing membranes are directly underneath a door operator, direct post-installed fasteners, such as screws, often result in blind and unsealed holes in the waterproofing. Screws auger through waterproofing, often concealed by shims or the mechanism itself. These untreated holes can void the warranty of the waterproofing system, but more importantly, can lead to leaks. With proper coordination and planning, project teams can provide sufficient vertical space in the detailing of the anchorage to result in both a sufficiently anchored closer and one that is also sealed in a watertight manner at penetrations.

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Typically, a pre-installed bridge is necessary to transfer the load from the operator to the structure without impacting the operator’s stability or the integrity of the waterproofing. A bridge can be achieved by extending the waterproofing under a reinforced concrete retainer curb (Figures 2A and 2B). The curb, anchored with dowels, is installed after the waterproofing is installed. This sequence allows waterproofing to be bonded to a stable penetration. Dowels are preferable to epoxy-set, all-thread rods. The dowels provide a smoother surface than thread rods, which force waterproofing to bridge and seal deep into the thread grooves.

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Elevating the operator over the waterproofing generally necessitates a penetration to provide power. Do not pass the wiring directly through the waterproofing; the small diameters and highly flexible wires will lead to failures. Flexible conduit, whether plastic or metal, carries the risk of stretching and rupturing membranes even with slight movement. A rigid conduit penetration, with sufficient clear height for a waterproofing termination, is the only reliable waterproofing practice.

An alternative approach to securing the door operator, while simultaneously making a compatible seal at waterproofing penetrations in-place, is to elevate the door operator above the waterproofing with steel stanchions or posts that can be wrapped with a conventional membrane seal at the plane of the plaza waterproofing. Waterproofing membrane manufacturers typically require this exposed vertical boot seal to be 152 to 203 mm (6 to 8 in.) tall. Unfortunately, the height of the waterproofing seal required here is often more difficult to achieve at the compact, low threshold entrances than when the reinforced concrete retainer curb is used.

The reinforced concrete retainer curb options and the generally less compact steel stanchion option require more vertical clearance that can, at least, locally require dropping the top of the structural slab.

Drainage requirements

It is also important to consider the drainage requirements of in-floor door operators. Similar to the issue of securing the door operator, drainage requirements are also project-specific and often explicitly delegated by the manufacturer to the installer.

Some designs include a four-sided depression for the operator, anchorage, and electrical penetrations. The depression cannot drain water out of the building. Therefore, the water is trapped in the depression, and the depression requires a drain (Figure 2A). Depressions without a provision to drain could result in a partially submerged door operator.

A submerged door operator typically violates the door operator manufacturer warranty, not to mention the waterproofing manufacturer’s requirements. While it is the responsibility of a project’s plumbing engineer to coordinate internal drains, door operator drainage may vary from conventional drains reliably sealed to the plaza waterproofing with clamping rings to drainage using plastic hose tubing routed to drain water away from the operator base. Plastic hoses penetrating the waterproofing system may not be a reliable watertight penetration and require specialized detailing. Concerns with flexible conduit penetrations are the same as those with flexible tubing penetrations.

Some designs can slope the waterproofing away from the in-floor door operator to an exterior area drain in the plaza waterproofing. Where interfacing with plaza waterproofing, designs that keep the operator a step above the remainder of the plaza keep the water from backing under the operator and contacting anchorage and power penetrations. While being a more straightforward installation, it also avoids detailing waterproofing connections to flexible hoses (Figure 2B).

Coordinate waterproofing across teams

As is often the case with multi-disciplinary designs and installations with high stakes for the building enclosure, coordination and active participation of the design and construction teams increase the chances of success. On the design team, the coordinating architect, structural engineer, plumbing engineer, and building envelope consultant all have roles to play. The general contractor and installers for the waterproofing, door and facade, plumbing, and electrical scopes will contribute to success with coordinated submittals and shop drawings. A pre-installation meeting is often the last good chance to get all parties together to review the installation and requirements for all systems correctly—and install them only once. The authors caution the project delivery method can also play a role in the coordination required, or lack thereof, to integrate floor closers into the building envelope waterproofing. The closer package is often part of the facade design building scope, whereas the waterproofing and concrete scopes are usually a more traditional design-bid-build delivery method. This straddling of delivery methods at the closer and waterproofing interface can complicate responsibilities. Design efforts may be asynchronous, leading parties on both sides to assume the other party will figure it out.

Carefully considering all aspects of in-floor door operators and adjacent waterproofing on a project is necessary to ensure both systems function long-term and do not negatively impact each other in service.

Authors

Daniel Gibbons, PE, is a principal with Simpson Gumpertz & Heger. He specializes in the investigation and design of industrial, commercial, institutional, and residential buildings for waterproofing issues including roofs, plaza areas, below-grade spaces, and exterior walls. He can be reached at dggibbons@sgh.com.

Matthew Worster, PE, is an associate principal with Simpson Gumpertz & Heger and is experienced in the investigation, design, and construction phases of building enclosure components on both historic and contemporary structures. He can be reached at msworster@sgh.com.

Source URL: https://www.constructionspecifier.com/how-to-waterproof-in-floor-door-operators/

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