Converting a DC rowhouse into two condos: which sprinkler system, one riser or two, and who maintains it after the sale

The two unit conversion is the most common flip in the District. A rowhouse on a narrow lot in Petworth, Trinidad, or Columbia Heights becomes a lower unit with the cellar and first floor and an upper unit with the second floor and often a pop up. Nearly every one of these jobs comes through our shop with sprinklers on the drawings, and most developers have the same three questions. Which standard applies, does the building get one riser or two, and what happens to the system once two strangers own the halves. Here is how we answer them.

Why the conversion brings sprinklers with it

A kitchen remodel does not add sprinklers to a rowhouse. A conversion does, because the job changes the number of dwelling units and usually guts the house to the studs on the way. DOB plan review treats a new unit as new dwelling space, and new dwelling space in the District gets a residential sprinkler system. If the project also adds a story, the pop up article covers that trigger on its own. Either way, the sprinkler sheets go in with the building permit set, and the permit steps article walks through what DOB wants on them.

13D, because two units is still a two family dwelling

Developers sometimes arrive expecting a 13R system because the word condo sounds like an apartment building. The building code does not care how the deed is cut. A building with two dwelling units is a two family dwelling, it stays under the Residential Code, and the sprinkler standard that fits is NFPA 13D, the same one a single rowhouse uses. That matters for the budget, because 13D lets the system skip closets and bathrooms under a certain size, run on the domestic water service, and go without a fire department connection or a monitored alarm. The 13D vs 13R vs 13 article lays out the full difference, and the rooms 13D can skip article covers the omissions. Three units is the line where 13R starts, so a developer who is tempted to carve a third unit out of the cellar should price that decision with the sprinkler change included, and not only the extra sale.

One riser or two

This is the decision that shapes the rest of the job, and it follows the water service. Two paths show up in DC conversions.

One riser costs less to build and only needs one backflow preventer and one annual test. Two systems cost more up front and are simpler to own, because nothing one unit does can shut off the other. On the older blocks the choice is often made for you: a house still on a half inch or three quarter inch lead service cannot carry two units of domestic water plus a sprinkler demand, and the service upgrade becomes the first line of the budget. The water service sizing article explains how that gets sized, and the multipurpose vs standalone article covers the loop option that works well in a small upper unit.

Where the riser goes when the cellar belongs to someone else

In a two unit conversion the cellar is almost always sold as part of the lower unit. If the shared riser sits in that cellar, the upper unit owner has a control valve, a main drain, and a gauge inside a neighbor's home. That works until the lower unit is rented to a tenant who does not answer the door, or until a head upstairs drips at eleven at night and the upstairs owner cannot reach the valve. We push developers to one of three answers. Put the riser in a common vestibule or a shared utility closet that both units key into. Put it in the lower unit with an access easement written into the condo declaration. Or build two systems so each owner controls their own. The third costs the most and starts the fewest fights.

Whichever one wins, the riser gets labeled. Each control valve carries a tag that names the unit it serves, and the head went off article is a lot shorter to follow when the valve says Upper Unit on it.

What the condo documents have to say

The declaration and bylaws are drafted by the developer's attorney before the first unit sells, and sprinklers are the item most often left out of them. Four things belong in there. Whether the sprinkler system is a common element, a limited common element, or part of each unit. Who pays for the annual inspection and the backflow test. Who pays when a head or a pipe inside one unit fails and damages the other. And the access rule for the riser if it sits inside a unit. The unit owner vs association article describes what happens in buildings where nobody wrote that down. A two unit association has two votes and no manager, so a silent declaration means the two owners negotiate it themselves the week something leaks.

One more District item. If the rowhouse had a tenant in it when the developer bought it, the tenant opportunity to purchase rules and the conversion rules under the housing code run on their own track, and the sprinkler schedule has to leave room for that process. That is a question for the attorney, not the sprinkler contractor, but it is the item that delays more conversions than plan review does.

The final inspection on a two unit building

DOB signs off the sprinkler system before the certificate of occupancy for each unit. The inspector walks both units and looks for coverage in every required room, the right head type for each ceiling, the backflow preventer and its test tag, the main drain discharging somewhere legal, and the riser labeling. The list of items that trip a final is in the inspection intervals and what fails article, and conversions add one of their own: a head in the upper unit that the lower unit's drywall crew boxed in during the stair rebuild. Walk both units with the drawings before you call for the inspection.

What it costs

A conversion is retrofit work, so it prices inside the $2 to $7 per sprinklered square foot range on the cost page. A house taken to the studs with open ceilings on both floors sits toward the low end of that band, because the pipe goes in like new construction. A conversion that keeps the plaster ceilings in the upper unit to preserve the moldings sits toward the top. Two separate systems add a second riser and a second backflow assembly on top of that. We quote a conversion only after walking the house with the architect's unit plan, because the riser decision moves the number more than the square footage does.

Quick answers