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“Does anyone have any experience with Bay Projection decks?”

by Prince Of Petworth April 11, 2017 at 1:15 pm 5 Comments

Bay Projection Deck with Roof

“Dear PoPville,

I recently bought a home in Capitol Hill and see many small decks on top of Bay Projections in the area and on my street. I currently have access to the top of my own bay projection through my master bedroom window, but no deck. I’ve reached out to a few design/build contractors inquiring about permitting and building a small deck there, but have not heard back (maybe the job is too small?). Does anyone have any experience with this? I’d love any advice: how to get it done, how long it took, how much it cost, who you used, etc… Thanks for your time!

FYI only I live in zone district RF-1 / Ward 6 if that helps”

  • Formerly Keefer

    I deal with a lot of old houses that have this feature and the first thing to worry about is water proofing, this little “balconies” are prone to leaking. So with that said I would start with a roofer. If the current roofing membrain is modified bit, “torch down” I would consider having it switched out to TPO or Rubber, and make sure all the flashing and seal under the door is good. From there I would look into the build the actual “deck”. Odds are there is only a small step down from the door to the existing roof surface, 4″-6″, you need to keep your “Deck” below the door sill to keep water from easily creeping under the door, snow is also a problem and you should make sure to clear it quickly in the winter. Building the “deck” is really just laying Pressure Treated Sleepers over the new membrain at 12″ spacing and then screwing your decking of choice to those. The deck isn’t actually attached to the roof just floating on it and held in place by the parapet. To that end when you are screening the decking to the to the sleepers you need to make sure to use a screw that isnt so long it would penetrate the roof membrain. Also explain to your roofer what you are doing, he might put a double layer off memebrain down because the “floating deck” can chaff. He will also tell you to keep some space between the sleepers and where the roof membrain turns up the parapet because this area of the membrain is the weakest spot. You should need a permit for any of this if you don’t want to get one the only part that becomes tricky is the railing, most likely for safety and the liability of people sitting on the parapet you will want a railing at 42″ above the deck, in a historic district this can be tricky because they will not want you to put one there, if historic it is one of those things I would just go and do and if caught ask for forgiveness. I have done simple rails that attach to the top of the parapet, just one or two horizontal bars that give you some security. Again explain what you are doing to the roofer and he will help you figure out a way to waterproof the fact that the railing will be making a few holes in the cap flashing.

    • Nathan

      Water is definitely a concern. The developer that renovated my house put one in and we had a leak that took quite a while to track down. Everything is fixed now and I love the balcony, but man that was a pain in the ass in terms of time off from work and contractor visits (thankfully all under warranty). After the leak was fixed they put in a double membrane.

  • The very first thing you need to do is to see if your property is in a Historic District. (much of Capitol Hill is).
    type in your address at the top and it will tell you if you are in a HD, and/or if your property is a landmark property.

    If it is, you should get in touch with the DC Historic Preservation Office before doing any work (or paying anyone to do any plans) as it may not be compatible/allowed in the HD.

    I would not do it anyway and ask for forgiveness later as Formerly Keefer suggests. The neighbors in CH are vigilant and will call in any illegal work.

    • Anon, A Mouse

      +1 Helvetica. I’m one of those CH neighbors, though not the calling in type. I just go to the meetings where my neighbors talk about paying $5000 in fines for un-permitted work, or watch one neighbor sue another for doing something legal, lose, appeal, lose, and sue the city…

  • DC Architect

    I’ve done plenty of these types of decks in historic districts in DC. I typically lay down a TPO roof over sleepers that slope to an overflow scupper, and drain it through a catch basin and downspout. Over the past year or so, DC has also adopted strict storm water runoff requirements, also known as the Green Area Ratio. It’s possible that during the permitting process you’ll get flagged under the Green Review, and DCRA will want to know how you are handling the runoff. If you get a proposal, I would add this into the contract as an itemized option if it comes up during permitting.

    It’s also possible to slope the roof towards the center of the walk out, and have a roof drain in the bay window roof. I don’t like to bring water back into the building if I can avoid it.

    If you live in Cap Hill, you most definitely are located in a historic district. To do what you are talking about, you’ll need a permit and DC HPRB approval. This type of thing is handled at staff level, so there is no presentation to the board required. If you decided to forgo the permitted route, you will most definitely get flagged by an inspector driving around, a neighbor or the multitude of HPRB members that live in Cap Hill.


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