According to the State Of Minnesota each town home is considered a separate building or dwelling. The exterior walls of a single family residence are required to have a 1 hour fire rated wall if the next house is less than 5 feet away according to R302.1. If you live in an inside unit town home, the next house is obviously less than 5 feet away. Since each unit is considered one dwelling, two adjacent town homes would each need their own 1 hour fire rated wall assembly. There are some exceptions though
- Two adjacent town homes can share a common 2 hour fire rated wall if there are no plumbing, mechanical, duct, or vent installations in the common wall. Electrical installations are allowed in the common wall.
- Two adjacent town homes can also share a common 1 hour fire rated wall if the town homes have a full sprinkler system.
To achieve a continuous fire rated separation R302.2.1 and R302.2.2 outline the requirements for the fire rated walls to extend from the foundation all the way to below the roof sheathing, and a parapet wall to extend at least 30 inches above the roof between the town homes. In the event of a fire that reaches the attic, these requirements will help slow the spread of a fire that goes through the roof of one town home, from igniting the roof of the adjacent town home. As always, there are some exceptions listed in these sections.
- If the elevation of the town homes differ by at least 30 inches, and the walls above the roof line are at least one hour fire rated (which is required) than no parapet is needed.
- No parapet is needed if the roof coverings have a class C fire rating (which most do), and the roof sheathing is fire rated treated plywood for 4 feet from the edge of the fire wall, or if the roof sheathing has 5/8 inch type X drywall applied directly underneath it for 4 feet.