Roof/ceiling under a deck

Hi there,

I am building a finished room (an extension of my living room) under my deck (deck is about 8-9 feet off the ground), but don't know how make the ceiling/roof. Removing the decking is not an option. How can I use the existing deck joists as the room's rafters and get it all waterproof?

Thank you so much!

 

You could build a roof using roofing tin like for a pole shed but it will have to be sloped to drain rain water. There are some systems out there that will give a nice finished "roof" and keep it dry.

Here is a good article I found the explains some of the systems that are out there: Professional Deck Builder: Under-Deck Drainage Systems
Be sure to scroll down to the "Ceiling Systems" section.

 

Sounds like a crazy idea. You will want to talk to some local roofers, but ONLY ones that are proficient with EPDM. (a rubber membrane) You would likely need to cover the entire deck with sleepers to give it some slope, followed by a fresh layer of plywood before applying the EPDM. Any door openings to the house, any stairs off of the deck and any handrails that protrude up through the deck surface or that are around the perimeter of the deck would be particularly difficult areas to seal, which is why this is a crazy idea. It would also likely need maintenance every 7-10 years. You'd also likely need to abandon the use of the deck... they could put traffic pads down on top of the EPDM but the wise course would be to avoid activity on the deck if at all possible. I'm not sure you should continue with this plan.

 

Thank you so much!!! Some of these systems look really good!

 

Adding a living space under a deck may not be the best idea. Think of the crud that falls through a deck. It will accumulate, rot and make things stink. Without a considerable pitch on the underdeck material, there won't be a "wash" factor. WITH a considerable pitch, you may lose living head space. It will need to be sealed from the elements as XSleeper said with EPDM, and of course insulated.
Another course of action is to remove the decking and install two layers (staggered) of 3/4" subflooring and apply a waterproof membrane similar to fiberglas with resin over the top. Several layers of the membrane and resin, and a final "walking" layer with a little grit in it. I built one for a client once, and he did the membrane thingy. I wouldn't touch it . Too much liability and not enough proven decks to draw from.

 

I agree with you guys as far as a membrane type thing not being a good idea. But the manufactured type systems that are designed to be installed from underneath appear to be a good option.