Originally Posted By: dvalley
This post was automatically imported from our archived forum.
Here is IRC code, this should give you your answer...
R317.1 Two-family dwellings.
Dwelling units in two-family dwellings shall be separated from each other by wall and/or floor assemblies having not less than 1-hour fire resistance rating when tested in accordance with ASTM E 119. Fire-resistance rated floor, ceiling and wall assemblies shall extend to and be tight against the exterior wall and wall assemblies shall extend to the underside of the roof sheathing.
A fire resistance rating of ? hour shall be permitted in buildings equipped throughout with an automatic sprinkler system installed in accordance with NFPA 13.
Each townhouse shall be considered a separate building and shall be separated by fire-resistance-rated wall assemblies meeting requirements of Section R302 for exterior walls.
A common 2-hour fire-resistance-rated wall is permitted for townhouses if such walls do not contain plumbing or mechanical equipment, ducts or vents in the cavity of the common wall. Electrical installations shall be installed in accordance with Chapters 33 through 42. Penetrations of electrical outlet boxes shall be in accordance with section R317.3.
The common wall for townhouses shall be continuous from the foundation to the underside of the roof sheathing, deck or slab and shall extend the full length of the common wall including walls extending through and separating attached accessory structures.
Massachusetts Certified Home Inspections
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