Opinion: Two unit townhouses

Subject: Two unit townhouses

Code:
2000 IRC Sections: R321.1 R321.2 and MR 1300

Submitted By: Uniformity Committee

Approved By: Thomas R. Joachim, State Building Official

Issue Date: December 2003

Question: Does the IRC permit the construction of 2 unit townhouses and if so, how does one arrive at that interpretation?

Answer: There are no two-unit townhouses. The IRC permits dwellings with 2 dwelling units and townhouses with 3 or more units.

Committee comments: The developer could use the IRC for the "two dwelling unit" structures, although the IRC would not consider those structures to be a "townhouse." The major difference is the fire separation requirements. Generally speaking, two dwelling units in the same building (on the same lot) require one-hour separation. Two dwelling units separated by a lot line require two one-hour rated walls at the lot line. A townhouse (three or more dwelling units) will be separated by two one-hour rated walls at the lot line (or imaginary lot line), or one two-hour wall. The two-hour wall provision listed in section R321.2, under the "Exception," does not apply to two-unit dwellings.
The scope of the IRC addresses "detached one and two family dwellings", which by definition, a "dwelling" can contain two "dwelling units." Such as a duplex (English language vs. code word). The scope of the IRC also addresses "townhouses," which is "a single family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and open space on at least two sides."

Subject:	Two unit townhouses
Code:	2000 IRC Sections: R321.1 R321.2 and MR 1300
Submitted By:	Uniformity Committee
Approved By:	Thomas R. Joachim, State Building Official
Issue Date:	December 2003
Question:	Does the IRC permit the construction of 2 unit townhouses and if so, how does one arrive at that interpretation?
Answer:	There are no two-unit townhouses. The IRC permits dwellings with 2 dwelling units and townhouses with 3 or more units.
Committee comments:	The developer could use the IRC for the "two dwelling unit" structures, although the IRC would not consider those structures to be a "townhouse." The major difference is the fire separation requirements. Generally speaking, two dwelling units in the same building (on the same lot) require one-hour separation. Two dwelling units separated by a lot line require two one-hour rated walls at the lot line. A townhouse (three or more dwelling units) will be separated by two one-hour rated walls at the lot line (or imaginary lot line), or one two-hour wall. The two-hour wall provision listed in section R321.2, under the "Exception," does not apply to two-unit dwellings. The scope of the IRC addresses "detached one and two family dwellings", which by definition, a "dwelling" can contain two "dwelling units." Such as a duplex (English language vs. code word). The scope of the IRC also addresses "townhouses," which is "a single family dwelling unit constructed in a group of three or more attached units in which each unit extends from foundation to roof and open space on at least two sides."