Townhouse Requirements
Building Permits
Single-family lots with proposed zero lot line construction require an RES residential building permit for each lot.
Multi-family lots require a CMI commercial building permit for each building (attached group of townhouse units).
Design Professional
Buildings with more than four dwelling units require an architect RCW 18.08.410
Buildings that do not meet IRC Prescriptive Design Requirements require an engineer RCW 18.43 and IRC R301.1.3
Egress Requirements
Emergency escape and rescue openings must have a clear path to the public way IRC R310.1
Any fenced area used as an egress path requires a gate.
Fire Sprinkler Protection
Washington State requires sprinkler protection when there are more than four attached units WAC 51-51-0313.
Sprinklers may also be required by the Fire Marshal’s Office when access or water flow are restricted.
Zero Lot Line Construction
When real property lines exist between units the following is required:
- Walls separating townhouse units on individual lots must be constructed as double exterior walls IRC Tables R302.1(1) or R302.1(2)
- Structural independence requires each unit to be designed as a separate building, as if no other units were present (i.e. no shielding from wind).
- Eaves or overhangs are not permitted to cross property lines, unless independently supported from the one-hour rated wall located on its own lot.
- Utilities are required to be located on the property served and may not cross property lines.
- Shared gutters and downspouts require a maintenance agreement.
Multi-Family Lot Construction
When multiple townhouse units are located on the same lot, separation can be either of the following:
- Common two-hour fire-resistant wall assembly IRC R302.2.2
- Double one-hour wall assembly IRC R302.2.1
Parapets, or exceptions to them, are required at dwelling separations IRC R302.2.5
RCW Construction Defect Disputes
This law was enacted as a result of rising insurance premiums and construction defect claims caused by water intrusion problems. The law applies to multi-family units, but smaller buildings may be exempt based on number of attached units and number of stories. There is also an exemption for townhouses where each building is located on a single lot. RCW 64.55
