Why Proper Glass Sizing Matters

 

When designing and fabricating glass for dormakaba’s MUTO Premium and Comfort systems, precision isn’t optional — it’s geometry in motion. Every MUTO configuration depends on the correct relationship between door width (DW), clear opening (CW), and track length (TL). These dimensions determine how smoothly the door operates, how fully it clears the opening, and how it aligns when closed.

The MUTO system allows a wide range of door panel sizes — from approximately 26 inches to 57 inches wide and up to 118 inches tall — but the geometry between panels, sidelite overlaps, and track length determines how it feels to the user. A door that’s undersized on paper may look fine, yet function poorly in the field.

 

From Math to Motion: Understanding MUTO Geometry

 

The standard dormakaba formula for a single sliding glass panel is:

DW = CW + 2-3/8” (60 mm)

This relationship ensures that when the door is open, the panel clears the opening while maintaining the required overlap on the closing side for privacy and stability.

When a fixed sidelite is used on one side, the formula adjusts slightly:

DW = CW + 1-3/16” (30 mm)

And when fixed sidelites are used on both sides:

DW = CW + 2-3/8” (60 mm)

These formulas are the foundation of MUTO geometry. They ensure that the DORMOTION mechanism, end stops, and carriers all engage properly — preventing binding, noise, or premature wear.

 

The 36-Inch Comfort Rule

While MUTO allows door panels as narrow as 26 inches, that’s a mechanical minimum — not a comfort standard. For real-world usability, plan for at least 36 inches of clear open width between the edge of the open door and any adjacent wall or sidelite.

This dimension provides:

• Comfortable, natural passage space

• ADA-friendly accessibility

• Visually balanced proportions for frameless glass doors

Even when the math checks out, undersized doors can make an elegant installation feel tight or awkward. The 36-inch rule ensures that the door not only functions properly but also feels right in use.

 

Fabrication, Not Cutting

In architectural glazing, glass isn’t “cut” — it’s fabricated. Once tempered, every dimension is final. That’s why glass sizing precision must happen during the fabrication stage, before tempering.

When preparing fabrication drawings, account for:

• The 7/8 inch (22 mm) height allowance for carriers and gaskets

• The 1-7/8 inch (47 mm) offset for ceiling-mounted applications

• Proper clearance for clamps, gaskets, and visible edges

Once glass is fabricated and tempered, there’s no margin for correction — precision now prevents problems later.

 

Clearance, Alignment, and DORMOTION Engagement

Incorrectly fabricated glass can affect DORMOTION alignment. If the door panel stops short or extends too far, the DM latch won’t engage smoothly, leading to inconsistent soft-close action or possible hook damage.

Proper fabrication ensures that the panel decelerates correctly in both open and closed cycles, preserving the smooth, quiet motion that defines the MUTO system.

 

Key Takeaways for Installers and Fabricators

 

1. Verify all geometry before fabrication using dormakaba’s formulas.

2. Always plan for a minimum of 36 inches of comfortable open clearance.

3. Use fabrication drawings, not cut sheets, to specify glass dimensions.

4. Account for ceiling recesses, sidelite overlaps, and DORMOTION zones.

5. Remember: once tempered, corrections aren’t possible — precision at this stage defines performance.

 

Bottom Line

MUTO glass sizing is geometry in motion — every millimeter affects performance, comfort, and aesthetics. By fabricating with the proper formulas and planning for full clearance, you’ll deliver the clean lines and effortless movement that make dormakaba systems stand out.

 

Explore the leading source for dormakaba MUTO sliding door hardware—discover products, resources, and expert insight at slidinghardware.com.