Deck over a slab

Mike Rathe

Member
Messages
22
Location
Columbia, SC
I have some questions for you guys,
Heres the situation, Im getting ready to put sod down in my backyard, and already have flower beds and all that good stuff, but all I have is a 12x13 slab of concrete that is pretty bad looking. I also added some pavers to make the slab a little bigger and give me some room for my grill, the pavers are in there with a sand/topping mix that gets pretty hard and these will not be easy to remove if thats what I want to do, they are bordered by 4x4's, the extra paver patio makes the total slab about 12 x 19. And these pavers are not perfectly level. So my idea was to put a small low deck directly over the concrete slab, I think this would just add a lot to the yard. So heres what I was thinking about doing. First I would put down several 2x4's running perpendicular to the house, I was thinking using a Powder Actuated nailer, Then I would put (5/4 x 6 x not sure yet) over the 2x4's. I think this would work fine and probably be able to get done in no time at all, but I dont want to only do this over the original slab, I want to make it big enough to actually use, but I am not sure what to do about the pavers and how I should go over these, I dont want to spend a ton of money on this project, but I want it to look good and do it right. Any suggestions on what you guys think I should do. Thanks a ton!
 
I have some questions for you guys,
Heres the situation, Im getting ready to put sod down in my backyard, and already have flower beds and all that good stuff, but all I have is a 12x13 slab of concrete that is pretty bad looking. I also added some pavers to make the slab a little bigger and give me some room for my grill, the pavers are in there with a sand/topping mix that gets pretty hard and these will not be easy to remove if thats what I want to do, they are bordered by 4x4's, the extra paver patio makes the total slab about 12 x 19. And these pavers are not perfectly level. So my idea was to put a small low deck directly over the concrete slab, I think this would just add a lot to the yard. So heres what I was thinking about doing. First I would put down several 2x4's running perpendicular to the house, I was thinking using a Powder Actuated nailer, Then I would put (5/4 x 6 x not sure yet) over the 2x4's. I think this would work fine and probably be able to get done in no time at all, but I dont want to only do this over the original slab, I want to make it big enough to actually use, but I am not sure what to do about the pavers and how I should go over these, I dont want to spend a ton of money on this project, but I want it to look good and do it right. Any suggestions on what you guys think I should do. Thanks a ton!


Mike,

Having built a low level deck myself I can try to offer some suggestions. Before I start, I have a question for you. Were abouts do you live? I don't need the exact location, but state, provence, region, or city/town would be helpful. My reasoning is that depending on where you are and your winter weather, will impact your foundation options/choices. Also are you planning on attaching this deck to your house or not?

Let me know and I will offer what I can.

Below is the link to my posting on my deck.
http://familywoodworking.org/forums/showthread.php?t=2970
 
IMHO... I have built a gallery of Decks in my time (having spent my summers buiding decks to make ends meet. and after retirement I built two for my son and 3 for my daughter and several for friends. ) I are well versed in the act of deckdom, but would prefer for your application a more solid foundation such as new concrete or Pavers or flaggs or tile over the high maintainance of Decking. Remember that in the hot humid area you live the sun will bake the deck as well as the intense heat will cook all moisture out. Although you don't have the winter freeze and upheaval that those of use in God's country endure, you have some intense summer weather to endure.

Iffin' it were me.... I would either replace the concrete (at about the same coast of a new deck or less) use decorative tile, or sand bed with Pavers, or textured concrete, and have a very low maintainance patio in lieu of the high maintainance decking of either wood or composite.
 
I too have built more then my share of decks and I'm with Bill on this one. I would add to Bill's comments an additional concern about using 2"x4"s for the joists.

Stained, stamped concrete really looks great and is much easier to maintain.
 
Hi Mike,
The guys offer some good suggestions but you live there and know how much trouble it would be to go concrete with the existing conditions. The concern over the 2x4 joist is real, unless you attach, during leveling, a leg to the ground rather often. You could use landscape timbers as legs and nail them to the 2x4 through the 2x4 side, or just lay a scrap piece of 2x4 on the ground, next to the joist and nail. I use 16 penny hot dipped galvanized for this purpose. you may have to clamp the leg while nailing to keep it snug against the 2x4.:dunno:
The landscape timbers can be cut on a miter box. I even use the landscape timbers as cross members between joists on some occasions, easy to hit with the nails :D and relatively cheap too.
Keep us posted and good luck.
Shaz :)
 
From your description, it seems that you'd have to lay the 2 X 4's flat on the slab, and then lay the 5/4 decking over them, for a total thickness of right at 2½ inches. That means there'd be no 'stepdown' from the inside of your house to the deck.

You'd have to fasten the pressure treated 2 X 4's directly to the concrete - probably using Tapcons® or a powder actuated nailer.

On the part over the pavers, you might need to remove a few pavers, dig down a foot or so, and pour some concrete footer blocks to support the 2 X 4's.

Overall, it doesn't sound like a good idea. The lack of stepdown could cause water problems in the house, and the overall longevity of the deck would be way less than a replacement slab - even with regular maintenance.

Seems like you'd be better off jackhammering up the old slab, removing the old pavers, and pouring a new slab the size you want. You could always dye and/or texture the new slab.
 
From your description, it seems that you'd have to lay the 2 X 4's flat on the slab, and then lay the 5/4 decking over them, for a total thickness of right at 2½ inches. That means there'd be no 'stepdown' from the inside of your house to the deck.

You'd have to fasten the pressure treated 2 X 4's directly to the concrete - probably using Tapcons® or a powder actuated nailer.

On the part over the pavers, you might need to remove a few pavers, dig down a foot or so, and pour some concrete footer blocks to support the 2 X 4's.

Overall, it doesn't sound like a good idea. The lack of stepdown could cause water problems in the house, and the overall longevity of the deck would be way less than a replacement slab - even with regular maintenance.

Seems like you'd be better off jackhammering up the old slab, removing the old pavers, and pouring a new slab the size you want. You could always dye and/or texture the new slab.

I'd sure like to see some pictures of the existing deck etc.

I basically agree with Jim, I think you would be ahead, to remove the existing slab, and then you could either make a new wooden or concrete deck.

I certainly understand the want to use what you got, and having to break up the old slab and haul it away is a LOT of work, not fun work either, I know, I've done a few.

I would look at a new deck, with a proper foundation, and then put some of that wood like stuff, as a wooden deck is a lot of work to keep up.

Good luck with it, take pictures! :wave:
 
Looks like Jim was the only other one that picked up on that height and that you were planning on laying down the tooby's. Jim hit on most everything I was thinking about. As a home Inspector I see a lot of rotten door frames at decks because of water splattering from them onto and into the door. Raising it up that high is really going to increase that possibility.

I think this is a bad idea. Time to back up and look at other options.
 
Another problem with the wood over concrete....getting it level and keeping it that way even over a relatively short time span.....say 10 years or less.

If it were mine....it's more labor intensive and more costly, I would remove the old concrete pad and start new.
 
Low decks can work, but i would NEVER lay a 2x4 directly on an exterior slab and nail it down. Moisture will collect between the slab and the wood, causing it to rot in no time. If this is directly off your house, i'd consider leaving a "landing" of the existing slab so that i can swing the door open. Then, i'd step up to a deck raised of of grade so that your joists are held of the ground a couple of inches. Using sleepers like you've described is building in a maintenance problem.
I've seen people float a deck on 12" square pavers. They build a frame of joists and support the joists with the pavers. The best installation i saw used aluminum 4x4 post bases epoxied to the pavers in order to hold the wood frame off of any water that might collect on the paver. Typical wood decking was attached directly to the wood frame. This deck was made with redwood and lasted 25 + years without anything more than typical maintenance (cleaning, staining, and sealing). Keep in mind that anything more than 18" above the ground will need a railing.
Another option would be to set new pavers directly over the top of your existing patio. What you have in place is about the most stable substrate you could have for a new layer of pavers.
Paul Hubbman
 
Top