Site Measurement for Frameless Glass Partitions: Tolerances Explained

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Measure the opening at several points in height and width, check for out-of-square and out-of-level conditions, and record floor finish and wall conditions before ordering. Frameless glass partitions leave little room for error, so the fabricator needs your measurements plus a tolerance allowance agreed in writing.

Why site measurement matters for glass partitions

A frameless glass partition is cut to size in the factory, so the opening it fits into must be known precisely. Glass cannot be trimmed on site without breaking, and any mismatch between the drawing and the real opening can mean a new panel and a delay.

Walls, floors and ceilings in existing buildings are rarely perfectly straight or level. Measuring carefully once, with the right method, saves time for everyone involved in the project.

What to measure before ordering

Take width and height at three points each: top, middle and bottom for height, and left, centre and right for width. Use the smallest value as the basis for the glass size, since that is the dimension the glass must fit.

Opening width and height at three points
Diagonal measurements to check squareness
Floor level at the glass line
Ceiling or structure above the partition
Position of doors, columns and wall outlets

Understanding tolerances

Tolerance is the small gap allowed between the glass and the surrounding structure, so the panel can be fitted without forcing it. The exact clearances depend on the glass type, the fixing system and the installation method, and should be confirmed with the fabricator and the project engineer.

Where a building is out of plumb or out of square, the tolerance must absorb the difference. Ignoring this is one of the most common reasons glass does not fit on the day of installation.

Checking floors, walls and levels

Floors may be finished after the glass is measured, which changes the final opening height. Agree with the contractor on the finished floor level and record whether the measurement was taken before or after screed or tiling.

Use a long spirit level or laser level to check the floor and the top of the opening. Note any step, slope or wall bulge in writing, with a photo, so the drawing can account for it.

What to send the fabricator

A good measurement package includes the dimensions at each point, a sketch with the orientation marked, photos of the opening, and details of the floor finish. Note which side is the finished face and where the glass will be seen from.

Mention any hardware planned for the partition, such as a door, handle or patch fitting, because these change the required cut and drilling positions.

Confirming the drawing before production

After the fabricator prepares a drawing and written specification, check that the sizes match your measurements and that the tolerances are shown. Approve the drawing in writing before production starts, since changes after cutting are costly.

If anything on the site differs from the drawing, raise it before approval rather than during installation.

Frequently asked questions

Should I measure once or several times?

Measure at least three points in both width and height. Walls and floors often vary, and the smallest dimension is usually the one the glass must fit.

Can glass be trimmed on site if it is too big?

No, tempered and laminated glass cannot be cut on site without breaking. The panel must be correctly sized in the factory before delivery.

Who decides the tolerance for a glass partition?

The tolerance should be agreed between the contractor, the fabricator and the project engineer based on the glass type and fixing method. Confirm it in writing.

What if the floor will be tiled after the glass is measured?

Record the planned finished floor level and tell the fabricator. Measuring before and after the floor work can change the final height, so timing should be coordinated.

Common mistakes to avoid

Measuring only once at one point and assuming the opening is square. Forgetting to account for floor finish or tiling that will change the final height.

Our recommendation

Take every measurement with the finished floor and wall conditions in mind, and send photos and a sketch with your dimensions. Approve the drawing and tolerances in writing before production begins.

Summary

Accurate site measurement at several points, with floor levels and squareness recorded, is the foundation of a glass partition that fits the first time.

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