Duplex separation — between units: code vs good practice

Code: 1 hr (½ hr sprinklered). Good practice: meet code.

3+ stacked units — between units: code vs good practice

Code: IBC + sprinklers. Good practice: meet code.

Code: STC 50 (IBC). Good practice: STC 55+.

Code: IIC 50 (IBC). Good practice: IIC 55+.

Code: fire-stopped. Good practice: meet code.

Code: no specific requirement. Good practice: separate.

Multifamily · Chapter 36

When people live on the other side of a wall or floor, code adds fire separation and good practice adds sound control.

IRC R302.2 · R302.3IBC 420 · 708IBC 1206 sound

36.1

Duplexes and townhouses fall under the IRC. Three or more units usually fall under the IBC, with stricter fire and sound rules.

Fire first, then sound, then privacy.

The rest of Between units: 3 more spreads, 16 drawings and 14 code citations, plus every other chapter, is part of the full fieldbook.

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