Ground Level Deck Over Sidewalk -

I recently got my hands on close to 1k sq/ft of 2x6 redwood from a deck that was being torn down. My plan is to use the redwood to build a pair of decks in front of my house. The deck at issue is going to be approx. 30x15, running from my front door to my driveway. I have a sidewalk which runs almost right now the middle of where I want the new deck, and if at all possible I'd just assume not remove it. Problem is, there is only a 4" gap between the top of the sidewalk and the bottom of my front door seal.

Here is my thinking - Dig out the entire area (except the sidewalk) a good 10" or so, use a series of concrete posts and beams leveled with the sidewalk, use 2x6 treated pine laying flat on the beams and sidewalk as my support lattice, fill the remaining dug out area with crushed stone (drainage), screw the redwood to the pine leaving 1/2" gap at the house/door.

Three questions -
1. Is this idea even sound?
2. Will I run into probles with rot due the pine laying across the sidewalk?
3. If I go with 2x6s flat, what should by maximum span be?

Thanks for any help or assistance.

 

1. No
2. Yes
3. Don't

Your home and site were not developed to have a deck there. It will have a short life.

What wil happen if the 10" hole filles with water, moisture or creatures?

If the redwood is in good condition (a few years left). you could sell it and use the cash for a different DIY project.

Just my opinion.

Dick

 

Thank you for the reply. I completely understand the site was not built with a deck in mind; however, I do plan on installing one and want to adapt for it the best I can.

I just wasn't sure about the sidewalk. Treated lumber is attached to concrete beams/footers all the time, so I know that is sound. I just wasn't sure if the fact that the sidewalk is 3' wide would become an issue. While I would like to avoid having to remove the sidewalk, I will if that is what needs to be done. I am also looking into a friends suggestion of using concrete and/or metal beams instead of lumber for the support structure.

There is a 3' flower bed currently between the sidewalk and the house. We already have an issue with flooding in that area (poor design, though installing gutters did help some). My thoughts were to dig deep enough and lay enough of a drainage barrier (much like a septic drain field - 10" was just an example for which I am open to suggestions) to keep water and mosture away from the deck. I do intend to divert/block water from the rest of the yard to prevent it from draining under the porch and rain barrels will divert roof water. This leaves just falling water, and if designed correctly, I shoudn't have an issue unless enough rain falls to flood me as it currently stands.

Thing is I am a yankee who came from a farming world of wrap around porches and large front of house decks. Now I live in Texas where the common answer is nothing but a sidwalk entryway and a small concrete porch in the back. I am married to this project . . . just looking to do it right.

 

Ditto what Concretemasonary said. You "want to do it right" -- do it with concrete. (I'm a deck contractor -- listen to the concrete contractor!!)

 

If you REALLY want a deck, instead of a slab, tear out the sidewalk as a starting point. Then excavate the area so that you have AT LEAST 6" from the dirt to your lowest PT wood member. You can use 4X6's for the girders at 6' O.C., use joist hangers to install your 2X6 PT joists at 24" O.C. BETWEEN those girders (THAT is your framing), and then deck it. You will be removing at least 12" of dirt.

Now, do the rest of the math, and think the thing the rest of the way through. At 15 X 30, that's about 17 yards, PLUS whatever you need to dig for your footings. The biggest problem is that you are pulling the dirt away from the foundation of the house. That is going to weaken the foundation along that side of the house. (The foundation relies on that dirt for support!)

Forget it -- pour a slab!!