Glossary / Type X

Type X

Gypsum board with a fire-resistance core used as a deemed-to-comply layer behind cladding. Type X is an assembly path. It is not an ASTM E136 pass for the visible siding.

Last verified 2026-08-23. JSON (CC BY 4.0)

Also called: Type X gypsum.

Related

• assembly
• noncombustible
• siding
• eaves
• Type X behind the covering
• Why Type X gypsum works
• Ignition-resistant versus noncombustible

Where this term is used

24 guides use this term.

• ASTM E119 versus a WUI wall test
• Bird blocks, boxed soffit, or unvented attic
• Char rate
• Craftsman eaves under R327
• Deck ledger and the wall intersection
• Deck railings in the WUI
• Exterior FRT wood and weathering
• Gravel and pavers under the deck

All guides →