National Terrazzo & Mosaic Association
NTMA terrazzo standards
NTMA guidance covers how a terrazzo floor is built up from the slab: the substrate it bonds to, the crack-isolation or waterproof membrane beneath it, the divider strips that lay out the field, and the matrix and aggregate that become the finished surface. Most of what decides whether a floor telegraphs cracks or delaminates is buried under the terrazzo and inspectable only before the pour, which is why the walk lives at substrate and strip stage.
Adoption varies by jurisdiction. Confirm the edition your authority having jurisdiction enforces before you run a walk against it.
What it covers
- Substrate flatness, cleanliness and moisture readiness
- Crack-isolation and waterproofing membranes
- Divider, control and expansion strip layout and setting
- Matrix and aggregate proportioning and placement
- Grinding, grouting and polishing sequence
- Sealing and final surface protection
What the evidence looks like
- Substrate photographed clean and profiled before membrane goes down, with any cracks shown as bridged or isolated.
- Divider strip layout photographed set to line and height before matrix is poured, since the strips are the only control joints the floor will ever have.
- Membrane coverage documented continuous at the perimeter and terminations before it disappears under topping.
- Ground and polished surface photographed under raking light for pinholes and pull-outs before grout fill.
- Sealer application recorded as placed and dated, not described after the fact.
Checklists that verify work against NTMA terrazzo standards
3 free checklists, each with the photo every item needs before it can be submitted.
Terrazzo flooring Rough-in· Terrazzo flooringTerrazzo flooring rough-in inspection checklistSubstrate, membrane and divider-strip layout verified before the underbed and matrix cover it5 items9 photosTerrazzo flooring Final· Terrazzo flooringTerrazzo flooring final inspection checklistGround and polished surface checked for aggregate exposure, pinholes and dull spots, with strips clean and the floor sealed5 items8 photosTerrazzo flooring Punch· Terrazzo flooringTerrazzo flooring punch checklistCloseout walk for cracks telegraphing at joints, dull or loose spots and strip damage from other trades3 items5 photos
Common questions
- What is NTMA terrazzo standards?
- Terrazzo systems: substrate readiness, membranes, divider strips, matrix and aggregate, grinding and polishing. It is published by the National Terrazzo & Mosaic Association. NTMA guidance covers how a terrazzo floor is built up from the slab: the substrate it bonds to, the crack-isolation or waterproof membrane beneath it, the divider strips that lay out the field, and the matrix and aggregate that become the finished surface. Most of what decides whether a floor telegraphs cracks or delaminates is buried under the terrazzo and inspectable only before the pour, which is why the walk lives at substrate and strip stage.
- What does NTMA terrazzo standards cover?
- Substrate flatness, cleanliness and moisture readiness; Crack-isolation and waterproofing membranes; Divider, control and expansion strip layout and setting; Matrix and aggregate proportioning and placement; Grinding, grouting and polishing sequence; Sealing and final surface protection.
- What does a field inspection against NTMA terrazzo standards look at?
- Substrate photographed clean and profiled before membrane goes down, with any cracks shown as bridged or isolated. Divider strip layout photographed set to line and height before matrix is poured, since the strips are the only control joints the floor will ever have. Membrane coverage documented continuous at the perimeter and terminations before it disappears under topping. Ground and polished surface photographed under raking light for pinholes and pull-outs before grout fill. Sealer application recorded as placed and dated, not described after the fact.
- Which edition of NTMA terrazzo standards applies to my project?
- Adoption varies by jurisdiction. Confirm the edition your authority having jurisdiction enforces before you run a walk against it.
- Which checklists verify work against NTMA terrazzo standards?
- 3 free checklists in the RTI library reference this family. Each is listed on this page with the photo evidence every item needs before it can be submitted.
A standard is only met if the evidence exists
RTI holds the submit button until every mandatory item is answered and the photos are attached, then chains the record so it can be proven untouched later.