@Danielle Polen I'm an Architect in DC and do at least 10 of these projects a year. I'm actually doing the permitting process for underpinning, an addition, and going to the BZA for an investment property I bought in the Trinidad neighborhood. There is a lot to do. There are two ways to get a permit.
1. No major structural items and the renovation is under 1,000 SF. DCRA will give a permit for these types of projects within a week of the application.
2. Everything else. Additions, dropping the basement slab, underpinning, converting a single-family residence to a two dwelling flat, a pop-up, and so on. This is what your project will fall under. The review process for this is between 2 - 4 months. Once an application is made the intake technicians will take a day or two to approve that the application correct. Then all the plans are uploaded online and then the intake technician reviews it again to make sure all the plans are there. If they are they send it to the different reviewers (zoning, structural, mechanical, DC Water, etc.). The reviewers have 30 business days (6 weeks) to provide initial comments. There is almost always one reviewer who takes the full 30 days. They tell me that they review the projects in the order they get them. If there are any comments it may take a day or a week to submit them back to DCRA. Now the reviewers have 15 business days to approve or provide more comments. As you can see this adds up quickly. This doesn't take into account if you have to submit to other agencies such as DC Water, DDOT, HPRB, DOEE, and so on.
Of course, before submitting plans to DCRA you have to do the design and prepare the construction documents to submit. The design phase can take anywhere from a week to many weeks. It depends how fast you can make up your mind and how good your architect is. The projects I complete in a week are usually for developers. They know exactly what they want and they don't care about the minutiae. Homeowners take much longer as it is a personal decision. They normally take 4 - 10 weeks.
Once the design is settled then the construction document phase beings. This is between 2 - 6 weeks. It depends on how complicated your project is and the availability of the other engineers. You will definitely need a structural engineer and maybe an MEP (mechanical, electrical, plumbing) engineer. This is also the phase all the forms need to be prepared and there are a few for rowhouse underpinning. You need the neighbor notification letter (within this letter there are three things to do), special inspection for underpinning (another two forms to fill), construction estimate, DC Water form to reuse the existing water meter and service line (if you add too many fixtures and you don't have a 1" meter you may have to upsize which then will require submitting more plans to DC Water), possibly an energy verification sheet (if there is an addition), a zoning data form, and a plat that is requested from the surveyor's office showing the existing structure and any proposed work.
On the fast track, a permit can be obtained in a little more than three months. However, as you know everyone has a project right now. For example, I don't have the bandwidth to start bigger projects until May. A lot of my colleagues are in the same situation. On the slow end, obtaining a permit can easily take six to eight months. I think you may be a little behind if you want to start construction in the summer. Maybe at the end of summer.
There is a lot to do however, it isn't really that hard. DCRA is not that bad and I like their online system. It is better than other jurisdictions in the DMV.
I'm happy to answer any questions you may have. Good luck.