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-   -   Leveling a deck (http://www.diychatroom.com/f19/leveling-deck-79470/)

denemante 08-23-2010 12:30 PM

Leveling a deck
 
Hey all,

The previous owner of our home did some regrading in the backyard 8 months ago. It appears they didn't re-set the deck correctly. It's sinking 3-4 inches on one end.

The deck is about 10 feet up and square. It's lag-bolted to the house. At the other end, it's supported by three 8x8 inch 10 foot long wood legs. These butt up to a 2x12inch header (two boards) running the width of the deck. On the ground, the legs go right into into the dirt, and it's unknown if there is any concrete down there, but it's doubtful.

I can easily jack the deck up to level. But then, two of the three supports are basically hanging there.

I figured I could dig around the legs, jack the deck to level, then just pour in concrete. However, I've heard this is not the correct solution as concrete directly around wood will rot? It's been suggested that I need to jack and dig - but basically pour/make a little a concrete pedestal under the leg for them to sit on. But then a portion of the leg would still be in the earth.

Alternately, there happens to be a cement patio under the deck. Presently, the three legs are at the outer front edge of the deck, and as noted, stand in the earth. But if I move them 1 foot closer to the house, they'd stand on the cement patio. So I could effectively just built three new legs and a new header/support, jack the deck and install it, then lower the deck on the new legs and cut away the old ones.

But I don't know if the concrete patio can take the weight. I assume I'd put little metal feet under the legs where they sit on the concrete.

Any ideas on the best-practice solution?

CoconutPete 08-23-2010 03:59 PM

You should have concrete as a base going down below the frost line and then having the post secured to the concrete base w/ some sort of anchor. Here is an example:
http://www.cornerhardware.com/articl...es/ar047_2.jpg

denemante 08-23-2010 04:29 PM

Excellent advice - but I have no idea where the frost line would be? I live in Georgia.

Ron6519 08-23-2010 05:44 PM

Quote:

Originally Posted by denemante (Post 490112)
Excellent advice - but I have no idea where the frost line would be? I live in Georgia.

This is a fairly easy question to answer. Use the search function and look it up. If this is an issue, fixing the deck will be impossible.
Ron

kwikfishron 08-23-2010 06:14 PM

Frost line in Georgia it 1 foot. I would suggest you dig down and find the bottom of your post (legs) and post some pictures of that and the rest of your deck here.

Yoyizit 08-23-2010 06:48 PM

I couldn't readily find this on the Web, but depending on the soil type and weight applied there is probably some minimum volume necessary for a footing. The footing shape is also important, wider at the bottom.
You may want to go deeper than 1' to get the necessary load bearing capacity.
To get the approximate weight on a post, divide the live + dead load on your deck by the number of supporting posts. For the dead load calc., wood weighs ~35 PCF.

epson 08-23-2010 07:30 PM

Ok just use a 6 diameter sono tube http://sonotube.com/ for your concrete forms. Dig 3-0 deep and pour cement in the tube and level it off at the top. Then place the anchoring system that Coconut Pete suggested into the wet concrete and let it set. When the concrete is set put your column in place and secure with proper fasteners.

denemante 08-24-2010 12:53 AM

Alright, I got dirty. I dug out two of the three legs (on the side that was down) and jacked up the deck. The legs were actually sitting on cement pre-cast footings (pyramid-ish in shape, wide at the bottom, and 4 nubs on the top around a square indent meant to hold the bottom of the leg).

The one that had sunk - this cement footer had tilted 30 degrees. I pulled it.

We may not keep this deck for more than a few years. Right now, I could stick something hard under the 4-inch gap that's now present under the leg as the deck is level while on the jack. The middle leg has about a 2 inch gap which I'd also fill. Is this safe?

Ron6519 08-24-2010 06:05 AM

"We may not keep this deck for more than a few years. Right now, I could stick something hard under the 4-inch gap that's now present under the leg as the deck is level while on the jack. The middle leg has about a 2 inch gap which I'd also fill. Is this safe?[/quote]
If by ,"10 feet up" you mean 10 feet off the ground, then this would not be a good idea. Unless what you do is structurally secure, this would not be safe.
Ron

Scuba_Dave 08-24-2010 07:53 AM

Also if the deck started to sag...
.....the connection at the house may have been loosened
I'd recheck everything
My Inspector wants a lag at least every 16" - between joists

Willie T 08-24-2010 08:11 AM

You have already experienced the bane of building in most of Gerogia... clay. As a substrate it is unstable and makes a poor base upon which to build.

Your local building department, or a local soil engineer, can tell you how to best prepare the area directly below your existing "pyramid-ish in shape" column bases. Yes, you can reuse them.


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