Specifying Considerations for Multi-Panel Systems: Thresholds and Components

It’s all in the details. Those pesky final steps in selecting a door, while often having minimal aesthetic impact, can still have important ramifications for the lifetime performance and efficiency of a multi-panel door system. Sills or thresholds need to be coordinated and should support both the door system and number of door panels. Thresholds should be selected based on weather exposure and floor transition.

Thresholds are available in at least three different profiles and should be specified according to the project design needs. Flush sills are designed to be recessed into the floor, creating a level transition between the finished interior floor surface and the exterior. Flush sills can incorporate the same finish flooring between the sill tracks. Flush sills offer seamless transitions and are a preferred solution for covered openings. Raised sills are intended to have a raised profile and sit up above the exterior. Depending on manufacturer, raised sills come in varying interior leg heights. Raised sills offer a greater degree of weather resistance. Raised sills, or special weather-resistant sills, are the preferred solution for weather-exposed openings.

Ramped sills are commercially compatible and offer ADA compliance when there is more than ½ inch change in the sill height compared to the walking surface. All threshold styles are typically thermally broken. The grade of material for the threshold should be specified, as well as the bearings, hinges, and wheels of the door panels. Nylon plastic and stainless steel are the most commonly seen materials. Stainless steel components usually offer the best durability and longevity for large or heavy door panels.

Photo courtesy of LaCantina Doors

Stacking multi-slide panels stack flush when fully opened. Aluminum wood multi-slide system shown with flush sill.

To control air leakage and improve energy efficiency, multi-panel door systems also rely on a mix of perimeter seals applied to each door panel. Top seals can be brush type to allow for the smooth operation of the door while still restricting the transfer of air and weather. The bottom or sill seal may be composed of low-friction coated rubber applied to the bottom of the door, creating a full seal yet allowing for the smooth operation of the door panels. Continuous seals along the edges of each door panel may be compression rubber gaskets, fin brush seals, or both. Careful application of high-grade seals provides a tight seal when the doors are closed and helps to maintain pressure and weather resistance.

Choosing a Manufacturer: Careful Attention to Key Characteristics Ensures the Best Compatibility and Performance

Product Design

As the aesthetics of the multi-panel door system will complement and enhance the overall design scheme, paying careful attention to looks is an excellent strategy when initially vetting manufacturers. Well-designed multi-panel system products should offer a balanced aesthetic and an adaptable size and hardware range, allowing them to suit each individual project. The ability of a manufacturer to maintain stile height and rail width across multiple door types means the ability to maintain a symmetrical, uniform appearance across a project and to keep daylight openings the same in a single elevation.

The manufacturer’s multi-panel door system should look and feel high-quality because that quality is grounded in real substance. The products should be manufactured with high-quality components and exhibit quality fabrication, resulting in an exemplary finished product.

Beyond the initial qualitative analysis, there are several ways to quantify and pinpoint high-quality multi-panel products. Particularly when specifying an appropriate multi-panel door system door for a green building, third-party testing performance criteria offer vital insight.

Each potential system should have an American Architectural Manufacturers Association (AAMA) Product Performance Class as well as a minimum design pressure (DP) rating. ASTM E-547 should test water penetration of multi-panel doors, with air infiltration testing via ASTM E-283 criteria. Each door should also be NFRC certified and labeled, allowing for clear representation of thermal performance (U-factor and SHGC), visible light transmittance (VT), and air leakage (AL).

The structural integrity of a multi-panel door system ensures that it will perform correctly over its lifetime. High structural integrity in door units will maintain proper fit and operation of the products under conditions of wind, rain, and other weather stresses. Structural load deflection testing is typically measured under ASTM E-330 and should be reported by the manufacturer. This test is used for standard doors as well multi-panel systems, with the results directly dependent on the size of the panels.

For commercial applications, AAMA publishes the primary standard for commercial windows and doors in its document AAMA/WDMA/CSA 101/I.S.2/A440-08: North American Fenestration Standard (NAFS)/Specification for windows, doors, and skylights. This standard defines four different product performance classes: R, LC, CW, and AW. It also identifies the minimum performance grade (PG) that is required to satisfy the criteria of each class. The defining criteria is the minimum design pressure (DP) that a unit must resist such that class R must withstand 15 pounds per square foot (psf) of pressure, class LC 25 psf, class CW 30 psf, and class AW 40 psf.

In addition, each class must meet minimum water-resistance test pressures ranging from 2.9 psf for Class R, 3.75 for Class LC, 4.50 for Class CW, and 8.0 for Class AW. ASTM E-547 tests water penetration. The specified sill configuration routinely has a direct influence on the results. The ability for the door as an entire system to either seal water out completely or to manage water so that any water penetrating the system drains away is analyzed under ASTM E-547. As an example, multi-slide glass doors have been tested using these ratings and standards and have been found to meet overall DP ratings of up to 45 with additional structural up to 90 psf and no water leakage at up to 6.8 psf.

Using both qualitative and quantitative measuring sticks offers a reliable gauge of the quality level of a manufacturer’s product line. The best manufacturers will feature performance statistics as hallmarks of their superior designs.