Washington DC Basement Digout/Underpinning

[Ian Carter]

Hey there,

We just purchased a townhouse in NW DC and are looking to convert the basement into a one bedroom rental. With ceilings of about 6'7", we are looking to digout and add at least 4-6 inches, if not 1-2 feet. I've read numerous posts on Biggerpockets with estimates and lessons learned in other cities, but nothing current in DC.

I'd love to hear any recent experiences digging out and underpinning in DC, including costs, contractors (referrals very welcome!) and tips. The basement currently has a separate back entrance but we'd look to add a front entrance as well as part of this project. As it stands now, as a studio, we can likely get about 1100 a month. A 1 bedroom will pull in about 2k a month. I'm hoping to move forward relatively soon but need to make sure it makes sense for the potential income it will generate.

Thanks!

[Eric Teran]

@Ian Carter depending on your budget you want to avoid underpinning. That can easily add $20k to $50k. I have two tricks that I use with my clients to avoid underpinning and getting your 7’-0” ceiling height.

You want your new lowered slab to remain equal to the top of the footing. Usually a footing is about a foot below the existing slab. This will get the head height and avoid underpinning. The other option is if the footing is only a few inches below the existing slab then you want to have the bottom of the new slab to be aligned with the bottom of the footing. Most footings in DC row houses are about 6” to 12” deep. This will give you the head height. However you will have a step all along the party wall at the bottom. Two of my clients were okay with this option as it was a basement unit that they were going rent it out. However, another client who was going use the basement as their personal space did not like it. For a rental I think it is fine.

In regards to the front door there are a few variables. 1-Is it a historic district? 2-Is the row house built on the property line (most in DC are) so that if you excavate to add a door you are n property? 3-Will this be a separate unit?

Google propertyquest and type in your address. It will give you a map with some of the property information.

FYI it will take 5 - 10 months to get a permit from DCRA from the day you have your Architect start. Five months is on the fast side.