22 August 2014

For homeowners: an open thread on "mudjacking"

If you own a house long enough, most of the components will need to be repaired or replaced (a fact often overlooked by young couples eager to purchase as much home as they can afford). Take my driveway.  Please.

Our house is only about 20-25 years old, situated near the crest of a hill overlooking woods.  It's clear that some regrading of the lot was necessary to position it where it is.  The driveway has a series of concrete slabs separated by tiny expansion grooves.  Over the past decade or so, some of the slabs have begun to shift.  These depressions first make themselves manifest in the winter when you are shoveling snow vigorously and the shovel comes to a sudden stop, sending a shudder through your body.

What's happening underneath may represent a "settling" of fill originally used to level the ground or perhaps some erosion as rainwater and winter meltwater work their way between the slabs, perhaps exacerbated by the burrowing of critters like chipmunks or the action of the roots of some nearby very large trees.

The traditional repair method is to hire a construction firm to jackhammer out the concrete, adjust the base as necessary and then pour new slabs.  The alternative is "mudjacking" (sandjacking, slabjacking).  This involves drilling a small hole in the concrete slabs and injecting under hydraulic pressure a material (originally mud or sand, but more recently a polyurethane foam) which fills the space and then lifts the slab until it is flush with its neighbors. (details at the link)

"Jacking" the slabs back up is generally faster, less labor intensive, less disruptive, and less expensive (probably by a factor of 3-5X - I'm still studying that) than removal and replacement of the driveway.  But when slabs are cracked (as some of ours are), there is a risk that the segments will separate, and even a smooth lift of an intact slab may not align perfectly with all the neighboring ones.

I'm writing this post to encourage readers who have dealt with similar driveway/sidewalk problems to respond with comments (for me and for other readers who have - or will someday have- the same problem to deal with), because this isn't the kind of information one learns in school.  Success stories and horror stories are equally welcome.


  1. I had one neighbor that broke up his concrete driveway into rubble with a jackhammer, left the rubble where it was, laid down more (and packed) sand and gravel over that and covered it with hardtop.

  2. I think that I have your experience beat Stan. I had a new home built in 1986, within the first year the slab that abutted the garage sank at one corner by approximately six inches, enough that with the aid of a flashlight I could see a distance of several feet under the garage slab itself. So, not only was the drive way improperly settled and packed, there was no earth support under portions of the garage floor. Unbelievably, it took some arguing with the builder to just poor a new slab - after I did the heavy work of jack hammering out the old. I sold the home six years later and up until then the garage floor remained intact, but I wonder if that has been so over the past 22 years.

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  4. I had a long strip of concrete replaced about 4 years ago. About 2 feet wide, 30 feet in length and sits right next to the house. The previous concrete strip had settled and had started to slope towards the house in some sections which is a big no-no. I did investigate mudjacking, but because the concrete was in bad shape in a lot of areas, I had it all removed and and replaced with a new correctly sloped slab. Still looks brand new.

    I would say if your concrete slabs are in relatively good shape, and there are no heavy loads traversing them regularly, mudjacking is a very viable option. You can save a considerable amount of money this way.

  5. A more permanent solution is using a continuous piece tarmac instead of concrete slabs.

    But more important would be to use a proper foundation. Dig below the local frost line, put in high quality, washed gravel (i.e. clean from anything the frost could destroy over the years), use a compactor to solidify the gravel and _then_ put the actual covering in place.

    In Bavaria, for small driveways, that means a total depth of 60 cm: 46 cm of gravel, 10 cm of rough tarmac, and covered with 4 cm of fine tarmac. While this is more expensive, it will last for decades even with regular (i.e. weekly) traffic from heavy municipal maintenance and service vehicles.

  6. I have a 20-year old concrete aggregate driveway that's cracked all the way across and I've been wondering what to do about it other than complete replacement. I'm trying to keep the weeds from growing in the cracks, but I'm afraid to pressure wash or do anything to clean it up because it's crumbling in a couple places. And of course being in the PacNW, there's moss **everywhere** no matter what you do. Ah, the joys home ownership!

  7. (Figured out the commenting problem, Privacy Badger wasn't allowing it.)

  8. you might borrow / rent / buy a grinder and grind down the edges so the high slabs are more or less flush with the low ones? alternately, clean the low slab surface and pour some cement in it to make a shallow ramp that will match to the high slab.


  9. Gotta love small towns -- I didn't experience this mudjacking myself, but it's involved.
    A few years ago I was at a local service club chatting with a couple volunteer firemen. They told a story about bringing a fire truck with a full water load to a friend's house a few years earlier and and backed it onto the concrete driveway. The driveway hadn't been properly installed and a couple of slabs were depressed.
    Someone else remarked that the house had been bought by "Sue and Jim". Another person noted that he'd just walked past that house and they were fixing the driveway today.
    Then I went to the grocery store and ran into "Sue".

  10. This is pretty standard in Ohio. You only end up with small -maybe 2"- holes with patched concrete. I work at a lot of commercial properties that use this. It's a proper fix for poor ground preparation and will last. And the small amount of adjustment needed in your driveway is perfect for this technique.

  11. May be a standard fix, but if the fill below the mudjacked area hasn't completely settled, you'll continue to get subsidence. Also, should your sewer line run under the jacked area, you risk a broken line from either the initial subsidence, or the increased weight of the concrete slurry. DAMHIK.

  12. Be sure to go with a reputable worker. The expansion of the foam has to be precisely calculated, otherwise it could go too high. If you have ever played with the polyurethane foam cans, you know what that stuff does.


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