Sliding doors are a feature common to many constructions. We see them in wardrobes and closets, shower doors and room dividers, in commercial buildings and offices, and even in restaurants.
The two mounting system categories most offered by manufacturers for both commercial and residential purposes are bottom-rolling and top-hung. This article outlines the main differences and benefits of both so you can make an informed decision as to which sliding patio door is best suited for your needs and objectives.
Alt text: Bottom-rolling sliding glass doors in a home
Features of Bottom-Rolling Sliding Doors
In a bottom-sliding configuration, the sliding panel is equipped with two rollers that glide on a floor track, and the top has two guides that slide in a guide channel.
The main characteristic of a bottom-rolling door is that the weight of the panel is balancing toward its lower half, making it potentially harder to operate depending on the materials (double glazed glass and solid wood frames, for instance, are heavier).
While they’re easy to install since they don’t require a strong load-bearing beam, and are relatively easy to use when properly designed and with quality hardware, bottom-rolling sliding doors present a few cons:
- The panels can be easy to lift off their track.
- Only the lead panel usually has a locking system.
- The bottom track tends to fill with dirt and debris, especially in the case of patio doors, which impairs the sliding motion. This adds to maintenance needs.
- Because the weight is not quite evenly distributed, regular use may lead to the bottom guides popping out of their channel frequently or jamming.
- It is fairly rare to see bottom tracks flush with the floor, at least not in standard configurations.
- Bottom-rollers slide straight, or at an angle. They are not an easy option for curved designs.
- The floor needs to be perfectly even to ensure smooth rolling. In case of uneven surfaces, the door may get stuck often, or simply not work.
If your ceiling is not strong enough to support the weight of top-hung doors, or if you have limited space for hardware, bottom-rolling sliding doors are your only option, unless you opt for structural transformations.
Alt text: Man installing top-hung sliding glass door
Features of Top-Hung Sliding Patio Doors
As the name suggests, a top-hung sliding door’s main feature sits at the top of the panel, where the sliding motion occurs thanks to wheels that glide in a fully concealed track. Typically, captive rollers are used to maximize stability. To avoid sideway swinging, the bottom of each panel rests in a narrow track channel. From top to bottom, those doors slide smoothly; the fact that the top track with the most important feature is enclosed and protected means less maintenance, and fewer risks of malfunction due to exposition to the elements.
Notable characteristics of top-hung patio doors include:
- The bottom track sits flush with the floor, eliminating unsightly guides sticking up and tripping hazards.
- Less hardware showing and smooth space transitions enhanced aesthetics and space flow.
- Less pressure is needed to operate, as the top wheels do the work without meeting resistance gravity.
- Even if dirt and debris accumulate in the bottom track, it is less likely to hinder use.
- As with bottom-rollers, the doors slide parallel to one another or at a right angle, which limits their use depending on the design of the room.
The main obstacle to top-hung sliding doors is that you need a strong aperture head to support the weight of the doors and the weight of the construction above, plus enough space at the top to encase hardware. If your house needs to be outfitted with a weight-bearing beam, the project can take more time than you anticipated and create more remodeling inconvenience.
Versatile Alternative: Folding Sliding Glass Doors
A third option that is an upgrade from top-hung sliding doors is folding glass doors, particularly suited for glass patio doors. The mechanism is the same as standard top-hung doors, with the added freedom of multiple configurations (all or a few panels may be fully open or partially open to play with airflow and look or shield from sunlight).
On top of the advantages of the standard top-hung mounting system, other benefits of stacking glass doors include:
- More design choices, including odd angles and curves
- Wider opening completely freeing up space and removing visual barriers
- Discreet stacking (1 inch-thick per panel) that leaves walls on each side completely free
- Possibility to open much larger expanses and redefine space
- Added security with each panel equipped with a locking system
When comparing the benefits of bottom-rolling versus top-hung systems for your sliding patio doors, keep in mind you are investing in a product you want to last. Here’s a quick checklist of items to research:
- How frequently do you plan on using the doors? Will they have to sustain a little abuse (say from over-energetic children)? If you answer yes to this question, the bottom-rolling system may not be the best option due to jamming.
- Are gale-force winds and heavy rains any concern? If yes, make sure materials and hardware are treated to withstand adverse elements.
- Is security a deciding factor? If it is, make sure and check the options of the locking system (lead panel vs each panel or possibility to add more).
- Is the choice of finishes large enough? Patio doors must be functional, yet still fit your style and décor, from glass color to track color and visible hardware coating.
- Is the orientation of the site subject to intense sun exposure? If so, low-E glass technology will protect your interior and prove more energy efficient than traditional glazing.
Installing or replacing sliding patio doors is a project you don’t want to undertake often. Be sure to consult with your contractor prior to committing, so no building constraints stand in the way.