Stacking Doors

Technical Details

The success of a Lift and Slide or Multi-slide door installation is very dependent on correct selection and design of the track and finished flooring system. This goes beyond just selecting the track type; it requires input and commitment from the architect and builder to ensure proper installation. Everyone involved in the project will benefit when the best possible system is chosen, prepared and installed. There are two basic categories of track systems for use with the sliding systems such as Pocket Doors, "Flush Track” and Thresholds".

Flush Track Systems

Flush track systems are the most popular in mild climates and can be tailored to most situations. A completely flush system is suitable for warm climates without snow build up, where it is customary to continue the interior floor elevation to the outdoors with little slope or drop. A flush track system which includes a small step and sloping drainage will work well in more challenging conditions. The flush track system allows for the minimum  interruption in finished flooring. In conjunction with the pocket configurations, flush track will make the door virtually “disappear” when fully opened. Depending on the amount of rain or snow experienced, and the amount of weather protection afforded by the surrounding structure, the flush tracks can be set up in two ways: completely flush (see Fig 1), or with a small step (see Fig 2 and Fig 3).

In either case the exterior flooring must be sloped to provide adequate drainage (minimum of 1/4" per foot) away from the door. In these installations it is critical that the dimensions shown on the shop drawings are carried through in the field. The track must protrude from the floor only the required amount, as the weather seal must seat on the finished floor. If there is any uncertainty as to the type or thickness of the finished floor at the time the door is ordered, then a stepped type of arrangement may be more suitable. Please note that sliding doors on flush tracks have some inherent limitations of the sealing systems . Lift and Slide doors do not have the bottom seal engaged when the door is lifted, and multi-slides rely on the finished floor as a sealing surface. Should there be water impingement on the floor from rain, snow, sprinklers, etc., the water will likely contact the interior finished floor. Water may also enter under the door in certain situations such as wind driven rain or direct spray from gardening equipment. In every case, we recommend use of water resistant exterior flooring such as tile or stone in the area around the door.

Figure 1:

This shows a completely flush track with no interruption in the floor elevation. It is critical that the finished floor details and the position of the tracks follow the shop drawings exactly.


Figure 2 and Figure 3 show alternate details using the flush track system. There are two advantages to these arrangements. First, there is improved drainage away from the home interior and second, the ability to design and install the door and still have some variation in the finish floor thickness (i.e. the step height may vary from design).

Figure 2:

This shows a flush track system with a small step toward the exterior. This helps to ensure any wind driven moisture does not enter the home. The exterior must slope away from the door.

Figure 3:

This arrangement provides a higher degree of security from water infiltration. The step functions like a threshold, yet allows for the "flush track" appearance.


Concrete Floors

Cast-in-Place Flush Track System: The T track is mounted on cross tires set in a pocket 2 1/2" below the slab elevation. The track is installed using concrete anchors and leveled, then the pocket is filled with mortar when the flooring is installed. See Fig. 1 above.

Tee Track on Concrete: The Tee tracks can be installed directly on concrete, eliminating the need to pour a pocket. The installation of the door is more complicated as the tracks must be individually laid out and leveled. The concrete work must be smooth, leveled and flat to ensure a good installation.

Pre-Fab Threshold in Gypcrete: The tracks come pre-assembled on a pressure-treated plywood base. The base is set and shimmed level on the sub floor and gypcrete is poured to the correct height. See Fig. 2 and 3 above.

Framed Floors

Flush track systems on framed floors are not a common occurrence. Generally, this type of construction is more suited to the threshold systems due to waterproofing issues.

Pre-Fab Threshold in Sub-Floor Pocket: A "pocket" is framed into the floor to accommodate the pre-assembled door still depending on the finished flooring thickness. This may only require elimination of the sub-floor and some additional blocking between joists. It is critical that the sub floor thickness and finished floor thickness is known at the design stage.

Figure 6:

Pre-assembled sill on framed floor system.

Tee Track on Sub Floor

In this case the track is fastened directly on the sub-floor. The installation of the door is more complicated as the tracks must be individually laid out and carefully leveled.

Figure 7:

Track mounted directly on sub-floor.


Threshold Systems

The threshold system allow for the best weather protection in areas with snow build-up or poor protection from heavy rains. The track is integral to the threshold, making a weather barrier similar to a standard patio door. Aluminum thresholds can be used in most non-pocketed configurations and some pocket doors. Generally, the door configuration is limited to three "active" tracks as the threshold step starts to become uncomfortably high with more than three tracks. In special circumstances, consult the factory for advice. Threshold systems without pockets install in a similar manner to conventional hinged or sliding doors.

Figure 8:

Threshold on framed floor.


When Thresholds are used on pocket doors, the exterior edge of the standard threshold is in line with the inside edge of the exterior wall. The floor area within the opening must be flashed and a threshold must be used.

Figure 9:

Threshold Extension for Pocket Doors.