Tile Substrate Flatness and Allowable Lippage (ANSI A108.02)
Whether a floor is flat enough to set tile on, and how much lippage between tiles is allowed afterward.
Example
You enter
- Tile's longest edge (in) 24
- Grout joint width (in, 1/16 or more) 0.125
- Gap under a 10 ft straightedge from the high points (in) 0.1875
- Gap under a 24 in straightedge, or 12 in for tile under 15 in (in) 0.0625
- Tile's allowable warpage (in, ANSI A137.1, from its data sheet) 0.03125
You get
- Limit 10ft (in) 0.125
- Limit short (in) 0.0625
- Short span (in) 24
- Lippage allowance (in) 0.0625
Checked against published worked examples from: Ceramic Tile Education Foundation (quoting ANSI A108.02).
Details, formula, and sources
Scopeby ANSI A108.02 as the Ceramic Tile Education Foundation quotes it. For tile with an edge 15 in or longer the substrate may vary no more than 1/8 in in 10 ft and 1/16 in in 24 in from the required plane; for smaller tile, 1/4 in in 10 ft and 1/16 in in 12 in, both read under a straightedge from the high points. Allowable lippage is 1/32 in at grout joints under 1/4 in and 1/16 in at 1/4 in or wider, plus the tile's own warpage. A 24 in tile at a 1/8 in joint over a floor reading 3/16 in under the 10 ft straightedge fails by 1/16 in and needs grinding or leveling first, and once set may show 1/32 in plus its 1/32 in warpage, 1/16 in. The standard is sold; the project specification, the tile maker's data and the installer govern.
Formula or tabletile edge >= 15 in: flatness <= 1/8 in in 10 ft and <= 1/16 in in 24 in; tile edges < 15 in: <= 1/4 in in 10 ft and <= 1/16 in in 12 in (from the high points); lippage = 1/32 in for joints 1/16 in to under 1/4 in, 1/16 in for joints 1/4 in or wider; allowance = lippage + inherent warpage.
Source and editionANSI A108.02 Sections 4.1.4.3.1 (tile 15 in or longer), 4.1.4.3.2 (smaller tile) and 4.3.7 (lippage), by name, as quoted by the Ceramic Tile Education Foundation and the trade press on 2026-10-19; the standard itself was not read (it is sold by TCNA).
Free accessThe Ceramic Tile Education Foundation quotes the flatness clauses free at ceramictilefoundation.org; ANSI A108.02 itself is sold.
What governsEstimate. AHJ and licensed professional govern.
API field namestile_edge_in, joint_in, deviation_10ft_in, deviation_short_in, warpage_in, limit_10ft_in, limit_short_in, short_span_in, lippage_allowance_in
- Secondary quotation values as quoted by CTEF and the trade press, not read from the standardceramictilefoundation.org
- Warpage entered the tile's allowable warpage under ANSI A137.1, from its data sheetstated assumption