What stroke width ratio is mandated for raised tactile letters on ADA compliant room signs?

Under Section 703.2.4 of the 2010 ADA Standards for Accessible Design, raised tactile letters require a maximum stroke width ratio of 15 percent of the uppercase letter "I" height.

Signage fabricators and commercial contractors face strict building inspections under federal accessibility mandates. Incorrect stroke proportions render room signs illegible to touch, leading to failed final occupancy inspections and costly punch-list sign replacements under ICC A117.1 standards.

If you only do one thing: Specify a medium-weight sans-serif typeface with a stroke thickness between 10% and 15% of the uppercase "I" height to satisfy tactile and visual criteria simultaneously.

• Stroke thickness ceiling: ADA Section 703.2.4 caps the stroke thickness of tactile characters at 15% maximum of character height, preventing thick relief strokes that obscure letterforms when read by fingertip.
• Character height bounds: Tactile characters must measure between 5/8 inch (16 mm) minimum and 2 inches (51 mm) maximum, measured from the baseline to the top of the uppercase "I".
• Tactile relief depth: Raised lettering must project a minimum of 1/32 inch (0.8 mm) above the sign background, typically routed from acrylic, cast in photopolymer, or precision-cut from aluminum.
• Character width ratio: ADA Section 703.2.3 requires character width to range from 55% minimum to 110% maximum of the uppercase "I" height, measured across the uppercase "O".
• Visual versus tactile dual rules: Dual-purpose signs serving visual and tactile readers must follow the stricter 15% tactile stroke maximum, whereas visual-only directional text permits stroke widths between 10% and 30%.
• Typographic styling constraints: Tactile characters must be 100% uppercase and sans-serif, prohibiting italics, script, oblique, heavily bolded, or decorative typefaces.

• Watch out for: Using bold font weights from standard font packages, which frequently push stroke thickness past the 15% threshold and fail ADA compliance audits.
• Watch out for: Carving characters with beveled or tapered draft angles that meet the 15% rule at the top surface but widen past the limit at the base substrate.
• Watch out for: Failing to pair tactile text with Grade 2 Braille placed at least 3/8 inch (9.5 mm) below the lowest line of raised text.

Review your sign artwork in vector layout software at 100% scale and measure the stroke thickness of the uppercase "I" against total cap height before routing acrylic or metal sign faces.