Waterproofing or Under-roofing a Back Deck

[glennmac]

I need ideas to prevent water from dripping through my back deck so I can store my tractor stuff under there and keep it dry.

The acre my house is on slopes downward from front to back. So I have a walk out basement in the back of my house. My wooden, traditional construction back deck comes off my first floor, so there is about 90" clearance underneath the deck. I park my brush cutter under there, some other implements, and sometimes my tractor. However, since the "roof" of this area is the floor of my back deck, water comes through the deck boards and accumulates on my implements and tractor. I would like to plug up this problem so I have a waterproof sheltered area for my gear.

I have thought of three approaches:

1. Put some sort of waterproof flooring on top of the deck floor. I am concerned that this would leave rainwater puddled up on my deck and start to rot things or seep into my house.

2. Caulk up the cracks between the deck floor boards. Same puddling concern.

3. Put some sort of "roof" underneath the deck floor boards. Water that seeps through the deck boards would then hit this roof, which would be sloped, and run off onto the ground. I could even project the sloping roof somewhat beyond the edge of the deck so the waterproofed area would be further enlarged.

If I go with the roof, what do I make it out of? Keep in mind that I can't get on top of it to nail on waterproofing materials. The "top" of the roof will be enclosed by the deck floor above it. I either have to waterproof the top of the roof before I even nail it up, or I have to waterproof the bottom of the roof after I nail it up. Keep in mind that I have no assistants, no home improvement experience, few tools, and few remaining muscle fibers.

Which makes me think about forgetting about wood as a material. How about plastic, fiberglass or metal. Those materials are inherently waterproof. I'm thinking I just need to cut them to the right sizes, attach them to the underdeck beams (nails?), and then somehow seal the seams between the several sheets it will take. This seam sealing issue also puzzles me.

Any thoughts will be appreciated. Simplicity and cost saving is my primary goal, not complex contruction or architectural beauty.

<P ID="edit"><FONT SIZE=-1>Edited by glennmac on 10/20/01 12:24 PM (server time).</FONT></P>

 

[JJT]

Do not caulk or roof the topside. 2 posibilities 1) Why not use metal roofing attached to the underside of your deck with a slight pitch it will work fine. 2) Better yet, if the deck's floor joists and posts are up to code - enclose the deck, creating a 3 season enclosed porch and gaining a dry area under the deck.

 

[TWINKLE_TOES]

glennmac,
<font color=blue>1. Put some sort of waterproof flooring on top of the deck floor. I am concerned that this would leave rainwater puddled up on my deck and start to rot things or seep into my house.</font color=blue>

I like this option. Cover the deck with 3/4 exterior plywood. Screw it down with galvanized square drive screws. You can furr it up (shim) to provide slope to address your puddling concern. Add flashings at the deck/house interface and at the run off from the deck. (they make flashings for this application) Cover it with the self vulcanizing rubber deck coat. Two brand names I have used are"Span Tek" and "Dec-O-Tek". Follow the manufacter application directions and you should have a care free deck. The disadvantage to this deck coat; gets hot in the sun. You won't walk on it in your bare feet.
Al

 

[scruffy]

Glenn, the most common method I am aware of is hanging metal sheeting under your deck at a slight slope. At the outside edge, install gutter and a downspout in the corner near a support post, anchor it and run down to the ground, thus preventing 'splashing' also. All under the deck will stay dry, and provide years of usage. Of course, I like the enclosed three season deck also...it would provide a much greater all season use of the deck area, as well as secure storage underneath.

 

[HalseyGreen]

Glenn - the lumber yard in town had a grand reopening this past spring, they had product called "Dry Space" it was a plastic type product that consisted of two parts, an "F" molding that was nailed unside down "F") to the underside joist of your deck at a slope, inside the legs of the "F" slid a flat panel that provided the surface for water to run off. Thought it was a neet idea and have thought about doing it under my deck to gain a dry space to store stuff, not sure the wife will let me put tractor stuff there. She has me building a shed for the lawn tractor and attachments right now, the only way I can get the stuff out of the garage to free up the other bay. The John Deere is in the other bay. I have also considered building a frame and putting metal or fiberglass roofing on top and hanging it under my deck. Since it should not be carrying much weight, connection at both ends should work. I will be interested in seeing what other ideas come up, maybe a solution I haven't thought of.

 

[hayden]

My inlaws had a porch roofed with semi-transparent corrigated plastic roofing. It comes in long sheets about 4' wide. It might be cheaper than metal, and it would let some light in from the cracks if that's of any interest.

If you do an under roof, take into consideration crud accumulation and cleaning. Lots of leaves collect on our deck this time of year and some percentage of them make it through the cracks to the stone below.

One thing you have going in your favor is that this underroof will not have to carry any snow loads, just support itself.

 

[Bird]

Peter, I've had lots of experience with corrugated fiberglass and plastic roofing; too much experience, in fact, and plan to never use any of it again. Maybe it's good in your area, but down here with our heat and sun, it looks good when new, but gets very dry and brittle, and cracks, crumbles, etc. when it gets to be just a few years old. And of course, it won't even get to be a few years old if we have just a little hail. Properly installed, it'll stand pretty severe wind when it's new, but once it starts to dry and get brittle, nails and/or screws will pull right through it. And my experience has been with 4 different types for 4 different applications and none of them were worth the time I spent, much less the cost./w3tcompact/icons/frown.gif

Bird

 

[GlueGuy]

My sister-in-law has had corrugated fiberglass (semi-translucent) skylights in her garage for about 15 years (at least) now, and they are hanging in there real well. She also has a "potting shed" area set up underneath her deck (which is a similar arrangement as yours). She used the same semi-translucent corrugated fiberglass as the skylights there to keep it dry. Seems to have worked a long time. The advantage is that it lets a fair amount of light through, but lets the water run out to the outside.

The GlueGuy

 

[PTRich]

My uncle put corrugatted plastic under his deck 15 year ago and it has lasted fine. He pitched it and it stops right before the end of the deck. He put rock under the edge where the water drips down. This seems like a cheap alternative to me, if the plastic is under the deck I do not think the sun breaking down the material will be the problem. (one mans opinion, I am a chef by trade.)

Good luck PTRich

 

[Bird]

Yep, if it's protected from sun, wind, and hail, it ought to work just fine (and it may work well in a cooler climate for all I know; just more trouble than it's worth here).

Bird