What does ASTM C635 / C636 cover?

Grid duty classification and main-runner load capacity; Hanger wire size, spacing and attachment to the structure; Seismic bracing, perimeter clips and free-end conditions; Support of light fixtures, diffusers and other in-ceiling loads; Grid level, squareness and installation tolerances.

What does a field inspection against ASTM C635 / C636 look at?

Hanger wires photographed at their true spacing and tied off correctly, before the tile is dropped in and the plenum closes to view. Perimeter condition documented against the seismic layout: fixed end, floating end, wall angle and gap all shown, not just the middle of the room. Fixtures and diffusers photographed with their own independent support, not left hanging on the grid alone. Grid level and square checked with the reading in frame, since a running error only widens toward the far wall. Duty class confirmed against what the ceiling actually carries, photographed at the main runner rather than taken on faith.

Which checklists verify work against ASTM C635 / C636?

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.

ASTM International

ASTM C635 / C636

ASTM C635 classifies the metal suspension systems that carry acoustical ceilings and C636 covers how those systems are installed. On site they are the questions asked above the tile line: is the grid the right duty class for what hangs on it, are the hangers spaced and tied the way the class assumes, and does the perimeter carry the movement a seismic layout expects. Every light and diffuser dropped into that grid rides on those answers.

Adoption varies by jurisdiction. Confirm the edition your authority having jurisdiction enforces before you run a walk against it.

What it covers

Grid duty classification and main-runner load capacity
Hanger wire size, spacing and attachment to the structure
Seismic bracing, perimeter clips and free-end conditions
Support of light fixtures, diffusers and other in-ceiling loads
Grid level, squareness and installation tolerances

What the evidence looks like

Hanger wires photographed at their true spacing and tied off correctly, before the tile is dropped in and the plenum closes to view.
Perimeter condition documented against the seismic layout: fixed end, floating end, wall angle and gap all shown, not just the middle of the room.
Fixtures and diffusers photographed with their own independent support, not left hanging on the grid alone.
Grid level and square checked with the reading in frame, since a running error only widens toward the far wall.
Duty class confirmed against what the ceiling actually carries, photographed at the main runner rather than taken on faith.

Checklists that verify work against ASTM C635 / C636

3 free checklists, each with the photo every item needs before it can be submitted.

Acoustical ceilings Rough-in· Acoustical ceilingsAcoustical ceilings rough-in inspection checklistGrid, hanger wires and seismic bracing set and above-ceiling MEP signed off before any tile drops in4 items8 photos Acoustical ceilings Final· Acoustical ceilingsAcoustical ceilings final inspection checklistTile installed level and clean, cuts and edge trim tight, seismic details complete across the field4 items7 photos Acoustical ceilings Punch· Acoustical ceilingsAcoustical ceilings punch checklistCloseout walk for damaged and soiled tiles, missing clips and level touch-ups after other trades finish overhead3 items5 photos

See the whole checklist library

Common questions

What is ASTM C635 / C636?: Suspended acoustical ceiling grid: classification, hanger wires, seismic bracing, installation tolerances. It is published by the ASTM International. ASTM C635 classifies the metal suspension systems that carry acoustical ceilings and C636 covers how those systems are installed. On site they are the questions asked above the tile line: is the grid the right duty class for what hangs on it, are the hangers spaced and tied the way the class assumes, and does the perimeter carry the movement a seismic layout expects. Every light and diffuser dropped into that grid rides on those answers.
What does ASTM C635 / C636 cover?: Grid duty classification and main-runner load capacity; Hanger wire size, spacing and attachment to the structure; Seismic bracing, perimeter clips and free-end conditions; Support of light fixtures, diffusers and other in-ceiling loads; Grid level, squareness and installation tolerances.
What does a field inspection against ASTM C635 / C636 look at?: Hanger wires photographed at their true spacing and tied off correctly, before the tile is dropped in and the plenum closes to view. Perimeter condition documented against the seismic layout: fixed end, floating end, wall angle and gap all shown, not just the middle of the room. Fixtures and diffusers photographed with their own independent support, not left hanging on the grid alone. Grid level and square checked with the reading in frame, since a running error only widens toward the far wall. Duty class confirmed against what the ceiling actually carries, photographed at the main runner rather than taken on faith.
Which edition of ASTM C635 / C636 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 ASTM C635 / C636?: 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.

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