Occupied deck over insulated, heated space – GreenBuildingAdvisor

Replies

1. 

   jhwehrli | Jul 10, 2025 01:39pm | #1

   What size/what kind of assembly is your roof framing and wall framing? Is this for a single family home? What climate zone exactly/where is it? Theres alot of needed info missing here for someone to suggest something.

1. 

   KBurnham | Jul 11, 2025 10:27am | #5

   Platform framing, open deck with roof, for the local fire hall, climate zone 5, Cariboo region of BC, Quesnel snow zone.

2. Expert Member

3. 

   AntonioB | Jul 11, 2025 09:46am | #3

   You’ve got a whole set of tricky issues to resolve here, with several solutions for each issue.
   
   I second DC regarding unvented roof. That also implies some kind of membrane roofing such as an EPDM or TPO membrane.
   
   The deck surface itself can simply be a wood deck laid over sleepers. These could be tapered the reverse of the roof slope so that the wood deck is flat. You’ll want to be able to remove decking here and there to be able to clean debris which tends to accumulate.
   
   If the deck has an open guardrail you’ll have posts that will most likely need to penetrate the roofing membrane in order to anchor into the roof framing. There is both a waterproofing and a structural issue that needs to be resolved here.
   
   If a parapet rather than an open guardrail is alright, then you can balloon frame the walls and parapet, which easily solves both the waterproofing and structural issue.
   
   In the past I’ve found a lot of good ideas and resources for these problems on the Fine Homebuilding website. I suggest you do Google searches with “Fine Homebuilding” and a particular topic such as “waterproofing guardrail posts”. You’ll find multiple solutions and can then choose among the best to adapt to your project.
   
   Fine Homebuilding allows you to read and download 2 articles for free each day without a subscription. I’ve attached one article for you.

   (AntonioB = The Artist Formerly Known as Jolly Green Short Guy)

   

4. Expert Member

   Akos | Jul 11, 2025 10:04am | #4

   Look at the detail here:

   https://www.builderonline.com/Design/five-smart-ways-to-build-a-better-deck_o

   Important bits is don’t poke anything through the membrane so any railing should be mounted to the deck or to edge mount spigots around the perimeter.

   If it is small deck you can avoid spray foam by edge venting around the perimeter. This does need a bit of extra height though.

   You can also go with rigid over the roof deck and use wider sleepers or paver pedestals to spread the load.