Sinking stoop

I have a 3x4' concrete stoop just under the side garage door. Since 1992 it has been sinking. About 1997 I dug under it, used a car jack, and put rocks underneath. It has been sinking and now is 6" below were it was. I'd have to remove some landscaping to repeat what I did in 1997. Is there an easier way? I can't be sure if the land is sinking or the builder buried refuge that is now decaying.
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Phisherman wrote:

I have the same problem except that mine isn't sinking that much. In my case at least, the land isn't sinking nor was there buried organic material. It's just that the damn thing is heavy and over time it...well, sinks. Rain water working away under it doesn't help.
I don't think your proposed fix will stop it from sinking. My plan - someday if I live enough - is to bust it up and put in a new one. The house side of the new one will go down far enough to rest that edge on the edge of the house footer; additionally, there will be rebar going from it into the house foundation blocks.
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dadiOH
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wrote:

What kind of car jack? If you use a floor jack this time, you might be able to do this even though there are some bushes in the way. It will go right under most of most bushes.

My stoop has sunk too. It may have stopped now, but it sank for 20 or more of the 28 years the house has been here. It had sunk some when I bought the house at 4 years old. And so have all or most of the other 15 townhouses that are in line with mine. And so have most or all of the 16 houses in line with ours in the next n'hood a quarter mile away. My stoop is P-shaped and 10 x 8 feet, so lifting it up is pretty much impossible. Some have cracked when they sank but not mine.
Houses across the street or up the hill haven't had this problem, I think, so maybe it has to do with being at the bottom of a hill, or maybe near the stream.
IMO there's no chance these were all built on refuse. It just wasn't packed down well.
Each neighbor has done something different.
I put 4 pavers, 2 stacks of two 12 or 16" square, and they come to the right height for the amount it sank.
Another n'bor paid someone to pour a step on top. The joker borrowed wire reinforcent from me, didn't bother to bring his own. I gave him the wire "sticks" used for the advertising signs I take down.
Another guy built a step or two with bricks in a pretty arrangement, which he surrounded by a rectangle of 2x4s. Looks nice except I wonder if it should be painted or if the paint will chip.
Others did other things, but all these stoops are bigger than yours.

I can't do that, it's 6 or 7 feet down.

A good idea. I hope it doesn't come to that for me.
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Phisherman wrote:

Maybe a hydraulic spreader. I'm sure you could rent one, or find something like this on ebay:
http://www.buffalohydraulic.com/product_155_1T_Hydraulic_Spreader.html
These can generate ton of force, which should help.
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Phisherman wrote:

    For what it is worth, I helped a neighbor who had a front 20 foot porch of concrete start sinking. We place several hydraulic car jacks under the porch with concrete bricks under the jacks. When the bricks stopped sinking and the porch reached the point when it was level, we removed one of the jacks and wedged more concrete bricks under the porch to fill the space. Of course we repeated this procedure with the other jacks. This was twenty years ago, and the porch is still level. The key I believe is getting the bricks to sink until the reach a stable place. Once they do, they will serve as a footing.
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Or add some solid (no cores) 4 inch x 8 x 16 inch concrete blocks on their sides along the edges to spread the weight.
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Just my humble opinion here, but I do NOT think this is a procedure that should be tried by the casual DIY. Getting Big Heavy Things up in the air is listed in the chapter entitled Stuff That Can Kill You If You Don't Know What You Are Doing. Even if you have the theoretical knowledge from a book, experience and trustworthy equipment (ie, no cheap chinese bottle jacks, please) plays a big part. One slipped piece of cribbing or one failed jack, at just the wrong moment, and any part of your body that is under the Big Heavy Thing is liable to have a very bad day. This is like working under a car on wobbly jack stands, only more so.
Faced with a similar situation, I be inclined to go with a mud jacking company, or at least a bobcat or small loader with fork attachments. Only way I'd think about doing it the hard way with small tools, is that if I had free or cheap access to all the tools and cribbing, and several willing and strong buddies to help out.
aem sends...
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How long did the sinking part take, after you started the repair? Did rainstorms make a difference?
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mm wrote:

    I am not sure if your question is for me or the original poster? In my case the sinking of the original porch took several years, getting a little worse each year until it needed to be addressed. The jacking and blocking effort only took a few hours with a few neighbors helping with the job. We laid a long flat board across the porch so that we could see we were not stressing one side more than the other and cause it to fracture. It really turned out better than we had expected.
    As for aemeijers comment about using the proper tools, that is always the best approach. In our case it was a "What have we got to lose?" approach. It most likely would have been a case of replacement rather than hiring a service to jack up the porch. Also, the way the porch was laid over the brick sides meant there was little chance of someone having it fall down on their limbs. We were well aware of safety and not about to volunteer to a project where we wish we had not, even if there was free beer.
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Thank you. I was asking you. I thought maybe the jacks continued to sink as the weight on them increased as they were pumped up, or even longer than that. But I guess not, which is good to know.

Would that really work? Would it show bending before it broke? (if that's what you mean.

What if the beer was put under the cement slab?
I haven't lifted a stoop, but I lifted a cement square from a sidewalk several times. I had 2x4's lifting up the corners and enough empty space dug out that getting fingers caught was unlikely.
I had a neighbor help me with the first square, and he came over with rubber dishwashing gloves! I provided him leather work gloves
He doesn't look weak. He's bigger than I am, but never came back when I kept saying it was a good time to put the square back. So I asked a skinny friend who's 60 years old. He had no problem and helped me put back one and later lift up the other next to it, and maybe put that one back too. But I hadn't cut out the tree roots enough and was embarrassed to ask him to come back, so I ended up doing it myself, with 3 4x4's to set it on and 6 2x4's, to lift it up and "row" it out, and then "row" it back, using a 2x4 as an oar, lifting the square and moving in one direction, then letting down the oar and bringing it back, and it was easier than making an appointment with my friend.
But even though the 2x4 was nowhere near breaking, I somehow don't think this technique would work if the stoop were much heavier than a sidewalk square, which it probably is. And not in this case if it has the bushes in the way.
I had all the wood already from privacy fences that neighbors had torn down and offered me the scrap.
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mm wrote:

    Perhaps I did make my self clear. Once the jacks were placed under the porch, they DID sink and continued to sink until they reached a firm footing. The process we used was to continue the jacking process and to insert another concrete brick each time the one under the jack sunk enough for one to be inserted. When the blocks under the jacks finally reach a firm footing, the porch slab started to rise. Since several jacks were being used, when the porch was finally level, we removed a jack and inserted concrete bricks to take up the space occupied by the jack.
    Once the slab was where we wanted it and one support in the form of concrete bricks was holding it up, the replacement of the other jacks with concrete blocks could also be done. What you ended up with was columns of concrete blocks serving as supports for the slab. Each of these supports had reached a point where they were on firm ground since the jacks used to sink them were now raising the slab when jacked up.
    The purpose of the piece of wood on top of the porch while the jacking operation was taking place, was to indicate when one side was being raised more than the other. In other words, it was allowing us to keep the slab level and not raising one side so much that stress would fracture the concrete slab. You may not need to do this with your project, but I just mentioned it in case someone would have such a problem. We did not want to crack the slab since it was still in one piece and if it could be raised and supported, a lot of work could be saved.
    The key thing in our operation was the forcing of concrete bricks (or blocks if more appropriate) into the ground until they hit a firm footing. While doing this we took pains to make sure we lifted the entire slab equally so that it did not crack, by using a piece of wood (straight edge) to show us when one side was going up more than the other. Once the slab had reached the level, each of the columns supporting it was concrete blocks that had been forced into the ground until they were past the soft ground. The rest was cosmetic in that the bricks on the front were patch so that they too supported the front of the slab. Not really rocket science, but a little planning saved a lot of money and came out well.
P.S. The beer tasted might good after it was done!!

    Yes, the concrete slab will bend before it breaks, and you can see it happening.

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wrote:
<snip>

I thought a long 2x4 or 4x4 might be the best way to lift the concrete square, then fill underneath with gravel, sand, or dirt. Probably safer than using a hoist/chain. There's no erosion in the area but there are plenty underground water veins.
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On Wed, 20 Jun 2007 18:48:39 +0000, Phisherman wrote:

Probably not an easier way but the cheapest for sure.. The land underneath obviously is sinking or you wouldn't be having a problem. :)
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Meat Plow wrote:

Not necessarily...more likely it is being displaced laterally. For a similar example, suppose you fill a bucket with small shot and then push on the surface with the end of a 2x4...it goes down, shot comes up/sideways.
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On Thu, 21 Jun 2007 10:16:15 +0000, dadiOH wrote:

Ok I'll run right out and buy some shot and give that a try :)
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Meat Plow wrote:

Sand will work too :)
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Brace it from the other side. With a GPS system you can pinpoint the exact location of the step, then it is merely a matter of finding the exact location of the back of the step in China. Have them drive some solid rod into the ground to force it back up. It may help for both of you to have a cell phone handy for the last couple of inches to assure they don't go too far.
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wrote:

Be sure to use high-temp alloy rods. You don't want it to melt in the middle.

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