Architects are often surprised when they learn that construction tolerances are permitted by the Texas Accessibility Standards, especially if they have just been informed by an over zealous inspector that a toilet will need to be moved one eighth of an inch.
Just look in section 3.2 of the Texas Accessibility Standards (TAS).
3.2 Dimensional Tolerances.
All dimensions are subject to conventional industry tolerances for field conditions.
In the new 2010 ADA Standards for Accessible Design (SAD), the permissible tolerances are more specific.
104.1 Dimensions. Dimensions that are not stated as “maximum” or “minimum” are absolute.
104.1.1 Construction and Manufacturing Tolerances. All dimensions are subject to conventional industry tolerances except where the requirement is stated as a range with specific minimum and maximum end points.
The biggest difference is the clarification that tolerances only apply when a fixed dimension is specified or when a maximum OR minimum is given. If a dimension is expressed as a range with a maximum AND a minimum, the field condition must be within that range.
Here are some examples of how construction tolerance could be applied (results may vary between agencies and inspectors):
| Element | TAS Requirement | TAS Construction Tolerance | 2010 SAD
Requirement
|
2010 SAD
Construction Tolerance |
| Water Closet | 18” o.c. fixed | 17” -19” o.c. | 16”-18” o.c. | No tolerance allowed |
| Ramps | 8.33% max
(1:12) |
May vary by 1% but average over a run should not exceed 8.33% | 8.33% max
(1:12) |
May vary by 1% but average over a run should not exceed 8.33% |
| Top of Dining or Work Surfaces | 28”–34” | ½” tolerance | 28” minimum and 34” maximum | No tolerance allowed |
| Door Width | 32” minimum clear | None. Manufactured door assemblies do not require a construction tolerance. | 32” minimum clear | None. Manufactured door assemblies do not require a construction tolerance. |
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And check back here to learn more about the upcoming changes.
-Jeromy
