Before moving to North Carolina, we lived in Woodstock, GA, which is a suburb northwest of Atlanta. The area we lived in was not much different from Southwest Wake. One of the similarities between the two communities was the housing boom. The “build ‘em fast and get them sold” ideology was the motto of many of the large builders. We bought a house that was a new construction home.
It was the first home that we owned, and we didn’t know some of the “tricks of the trade” that subpar builders will do to prepare a piece of land ready to be built on. In our case, the lot was cleared, backfilled, compacted, then built on.
The first problem was when our water bill tripled in one month. Although there was no noticeable difference in water pressure, we knew something was wrong, and after finding no leaks in the house, called a plumber. We discovered a break in a main water line right outside of the foundation. The plumber said he thought that something had shifted in the land causing the break in the water line coming into the house. We had the line replaced, then decided to look at what could have caused it. At the time, we saw nothing obvious, and forgot about it.
We had noticed that in front of the house, the walkway leading to the front steps had settled slightly. Water was pooling on our sidewalk where it hadn’t in the past. We also saw that it had separated from the front steps by about 1/4 inch. The walkway connected to the driveway, which had also shifted, noticeable because it had dropped about 1/2 inch from being level with the garage floor. There was one crack in the driveway, and one in the garage. The cracks didn’t really bother me, and I justified to myself (and my wife) that the house is going to settle over time. Little did I know that my lackadaisical approach was the worst thing I could have done.
The surprise came when we put the house on the market. The first inspector saw the settling and told the buyer to run if it wasn’t fixed immediately. We realized that we were not going to be able to sell the house until we had it fixed.
Like the illness that you’ve never heard of until you know someone who’s afflicted, we soon learned about what causes driveways to crack, and walkways to separate from the foundation.
When we fixed our issue in Atlanta, it took over forty cubic yards of mudjacking slurry to fill the voids under the driveway, garage floor and walkway. “Mudjacking” is the common term for pumping a slurry through 2” holes drilled in your sinking concrete, and filling them until the slab rises. The slurry is a mixture of topsoil, sand, water and some concrete to hold it together. The process only took a day to inject, then another 2 days to dry.
There are some reported cons to mudjacking. The slurry mixture is extremely heavy. If you already have issues with loosely packed soil or eroding soil under your slabs, you’re adding a lot of extra weight on top of that soil. The slurry can weigh about 100 pounds per cubic foot. In my case in Atlanta, it took over 1,000 cubic feet of slurry. That’s A LOT of weight to add to already volatile soil. Further sinking can pose a real problem, because now the slurry has to be drilled through to fix the problem.
The other way to raise the slabs is through a similar process, but using polyurethane foam instead of slurry. The foam requires smaller holes to inject, as well as fewer holes. Since it’s a foam, it can also fill the cracks and crevices better than the slurry.
The weight of the foam is only about 2 pounds per square foot, as opposed to the 100 pounds of the slurry. The foam is also resistant to water erosion. If your area has water running under the slab (often the cause of the initial problem), the foam may be a better option as it will not break down with exposure to water like some of the slurry mixtures can. Foam also hardens and dries in about 15 minutes, as opposed to the mudjacking which will take a couple of days. The polyurethane is lighter, arguably stronger, and a better long-term fix to the problem.
There is an urgency to get this done. If the slab or driveway gets to a point where it’s too broken up to lift, then you’re looking at getting a new driveway poured. That will increase the cost of your repair 10-fold.
Early detection is key. This is not the type of item on your honey-do list that needs to rest at the bottom, unless you have $20K sitting around for a new driveway; or worse – foundation.
Here’s what to look for:
Are there obvious areas of the slab that are not level?
Is the driveway level with the entrance of the garage?
If you have a culvert at the bottom of your driveway, do you see a washout of soil next to the concrete?
Check the weather stripping at the bottom of your garage door (when the door is closed). Is the space greater on one side?
Is your porch concrete pad even or higher than the border around it?
Is your porch or patio sloping toward your home?
Is there a separation between your walkway and the front step to the house?
Any of these issues could lead to a much larger one. I didn’t deal with this issue until it was time to sell my house, at which point I lost my first buyer because of it. Had I understood the issue, I would have had it repaired earlier, and it would have cost me less money. The price to get your void filled will likely run between $1,500 and $3,500. I went with the mudjacking solution as it was the only one available in my area at the time. This is one of those cases where ignored small problems WILL become larger ones if not addressed. If you’re not sure if you have a problem, call a professional.
