Looking Up: Third-Story Pop Ups on Rowhouses




We have found that third-story pop-ups on rowhouses are becoming more popular in Washington DC because the influx of people moving to the city and the density of neighborhoods means rowhouse owners either have to go up or back to gain the additional square footage they desire. Homeowners don’t want to move to gain additional space because they like their neighborhood or their kid’s schools. Most want a third-floor addition for a new master suite. However, if you’re looking for a larger family room, a third-story addition doesn’t make sense. Some turn to third story additions because zoning rules may limit the size of a rear addition. This applies to rowhouses and semi-detached houses. General rules for a rear addition are:

  • With zoning you are limited to a 10-foot addition on the back or no further than 10-feet past your adjacent neighbor’s rear elevation.
  • The Floor Area Ratio of the zone where your home is located can limit the rear addition size to 40%, 50% or 60% of your total lot size. A third-story addition does not affect FAR. In general, as a right, you can add a third story to two-story rowhouses. There is a 40-feet height limit. Structurally, we have found that almost all two-story rowhouses can carry the load of a third floor, but to confirm this, we will (and DCRA requires) dig test pits to verify that the existing footings, foundations, and soil conditions will support a third floor.

Design and Construction Considerations & Challenges for Third-Story Additions

  • Some rowhouses have existing additions or sleeping porches that have been converted into four-season rooms. However, some of these rooms may have been poorly built, and/or the joists may be undersized and can’t support a third story that extends over the existing addition. We may opt to build the addition only on the main house.
  • Our design team never wants the addition to look like a box was plopped onto the house. They work very hard to make sure the front elevation blends with the entire block of houses, especially if your house is the first to add this level. We can use several architectural tricks to make the addition look less imposing from the streetscape. The addition can be set back and have a front porch or hidden behind an existing mansard roof or by adding a shed or hip dormer.
  • Constructing the third floor requires completely removing the existing roof. We usually must upgrade the 2nd floor-ceiling joists as they are not usually sized for this load. If there are HVAC air handlers on the roof or equipment in attic spaces, these units must be moved to the new roof.
  • We analyze the HVAC/mechanical to decide if the existing systems can serve the new floor, or if we must create a second or third zone. We must also sometimes heavy-up the existing electrical panel to support electric on this level or add a subpanel.
  • The best place for stairs to access the third story is stacked over the existing stairwell in the house. To build the new stairs, we often extend the second-floor hallway into an existing bedroom and closet, so that room shrinks in size. However, with that said, many of the staircases in older homes do not meet current building codes. They are often narrower and steeper, or the hallway is too narrow, which means our architects will have to find other locations.
  • If a client wants a roof deck on top of the addition, we can also build stairs from the new third floor to access the roof. Sometimes the addition covers a portion of the plan and a roof deck is placed behind the addition. We find that clients that have a nice rear yard don’t usually want this option.
  • Having cooperative neighbors is also an advantage for the construction of the addition. Of course, neighbors are informed as part of the permit process. Ideally, they will give us permission to use their roof when we need to build the sidewalls of the addition. If your neighbor has a chimney that is adjacent to your roofline, that chimney will need to be extended. There are other more complicated issues with neighbors’ roofs, but we would need to analyze that on a case-by-case basis.
  • Houses in historic neighborhoods are particularly challenging, and in some cases, third-story additions will not be approved. Every situation is unique. Historic districts require these additions not to be visible if viewed from across the street of the front façade. This rule also applies to end units where the side of the house is visible from the street. In some cases, this even affects the view from the rear of the rowhouse, for example, if there is a gap in structures behind the house and the rear is visible through this gap. Many times, after we present our research, clients decide the addition is not worth the effort. If the addition must be set back from the front façade, this can limit the addition to such a small percent of the footprint of the house that the extra square footage can’t be fully utilized as the client wants. Historic staff will usually advise you as to the likelihood of being granted permission. Georgetown can be a particularly difficult place for an add-story because of a notoriously unpredictable historic body called the Old Georgetown Board.

Landis has a design team well-versed in zoning rules and an in-house permit expeditor. We know DCRA, ANCs, and historic committees can be difficult to work with (Chris Landis served two terms on DC’s Historic Review Board), but we can’t guarantee approval.


Our third story pop-ups range from $300,000+ . This includes a bedroom, closets and full bath and some work modifying the 2nd floor for the stairs if necessary. An addition like this can increase the future value of your house by 25 to 30%, so it can be a good investment, but you should research comparable home sales in your neighborhood. You can consider borrowing the money using a loan to future value where banks compare your finished project against houses of similar size.

Homeowners considering a 3rd floor are often deciding to “love it or list it.” If you love your neighborhood or your kid’s school and your neighborhood supports your investment, it may be a good decision. Remember, moving laterally costs at least 10-12% of what your existing house is worth or more in fees and moving costs. Thinking about a third-story addition? Give us a call at 202-726-3777 to discuss your options and maybe set up a site visit. It’s helpful if you send us a plat to review.


The rear of a third-story pop-up on Capitol Hill. We also bumped out the rear of the house by a few feet.

Though the house was in a historic district, the house itself was not considered historic because it had been built on an empty lot in the 1960s.


The front of that same house. The third story raised the roof to about the same height as the neighbor’s house.

Read more about the above project and see interior photos by clicking here.

We’re currently finishing up another third-story addition in the Glover Park neighborhood.


A wider shed dormer replaces an existing small dormer set in the roofline.

This new floor has a primary bedroom and bath suite with generous closets, as well as a second bedroom.


In this under-construction of the rear of the Glover Park addition, you can see the structure and Tyvek barrier.

Read more about the above project and see interior photos by clicking here.

Framing the 3rd story addition

As seen from the front of the house.

The addition is seen from the rear.

The structure is clad in James Hardie fiber cement siding. We opted not to extend the addition over the two-story sleeping porches that have been enclosed. We stopped at the original house rear wall.

Stairs to the new third floor.

For this project, we did not stack the stairs to the 3rd floor over the 1st to 2nd-floor stairs.