Known formally as Torre di Pisa (the Tower of Pisa) the region’s most famous piece of architecture has been leaning for hundreds of years. At its worst, the angle was about 5.5 degrees. However, stabilization efforts have reduced it to just about 4 degrees.

How was the lean reduced? Through several methods, none of which was slab jacking. We suspect that slab jacking was not utilized due to the nature and condition of the underlying soil. Keep reading to learn more about that.

200 Years of Construction

Many people do not realize that the Tower of Pisa took nearly 200 years to complete. Construction began in 1173 and was not completed until 1372. You might also not know that the leaning did not start after the structure was complete. It actually started just six years after construction began.

Builders had barely begun work on the seventh floor when they noticed the tower sinking on one side. A subsequent investigation revealed the soil underneath was too unstable. With a foundation of just 3 meters and heavy marble being the primary construction material, the tower was too heavy for the soil.

Constructed was halted for almost 100 years in order to allow the soil to settle. Some believe the tower would have eventually toppled had engineers not taken a break in construction.

Fears of Eventual Collapse

Construction was eventually completed in two more phases. The tower was opened to the public and soon became the centerpiece of the region. Over the next several hundred years, it was used for everything from scientific experiments to religious services. It was also used for military operations.

During World War II, the Germans were suspected of using the tower as an observation point. But because it was so important to Pisa’s architectural history, Allied forces decided not to destroy it. Fast forward to the 1960s and engineers began expressing genuine concern that the tower would fall over.

Shoring It Up

This brings us to how the tower was ultimately saved. Engineers knew they had to do something, or the tower would come down. They first tried attaching tons of counterweights to the high side in order to pull the tower back.

That effort produced limited results and the tower was closed to the public in early 1990. Its bells were also removed to take some of the weight off. Finally, engineers hit on the right solution: they decided to remove soil from the high end of the tower. This not only reduced the tilt to 4 degrees, but it also prevented the tower from leaning any further.

It turned out to be the correct solution for a curious reason: the soft soil is responsible for keeping the tower standing despite numerous earthquakes. The same problematic soil causing the tower to lean was also keeping it erect. This is why slab jacking was determined to be inappropriate. Engineers wanted to keep the soil as-is so as to not increase the chances of future earthquake damage.

In the end, removing soil accomplished the same thing as slab jacking, just in reverse. Rather than filling in voids underneath unstable soil, they created new voids on the other side, thus encouraging the structure to level itself. And now you know.

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In previous posts we have talked about what causes sinking concrete. This post will deal with cracking. Though the two are often related in real-world settings, they do not have to be. A perfectly level piece of concrete can still crack. Likewise, a concrete slab can sink without cracking.

Compressive Strength vs. Tensile Strength

Concrete is a composite material consisting of fine aggregates, coarse aggregates, binder, and water. A concrete manufacturer might start with sand as the fine aggregate. Gravel is added as the coarse aggregate while Portland cement is the binder. Everything is mixed together with water to create the finished product.

As a composite, concrete is fairly strong. But there is a rub. There are two types of strength we are concerned about when it comes to things like concrete slabs, staircases, and larger structures. The first is compressive strength. The second is tensile strength. Concrete has a very high compressive strength but a comparably low tensile strength.

Compressive strength is the ability to withstand compression, or dead weight if you will. Tensile strength is the ability to withstand the force of being pulled in one direction or another. In the industry, we call this force ‘load’. Tensile strength is measured by putting a material under load and seeing how much force can be applied before it breaks.

More often than not, concrete cracks because its tensile strength is exceeded. Forces pull it in one direction or another until cracks appear. Sometimes, a force that seems to be pushing on the concrete (rather than pulling) results in failure.

Thermal Expansion

Concrete exhibits a comparatively low coefficient of thermal expansion. This is to say that it does not expand or contract a great deal when exposed to environmental conditions. However, expansion and contraction still do occur to some degree. If accommodations are not made to counter it, repeated cycles of expansion and contraction will lead to cracks.

The thermal expansion issue explains why concrete driveways and patio slabs in northern environments crack after just a year or two. The repeated freeze-thaw cycles of winter weather put too much stress on concrete slabs.

Concrete Shrinkage

Finally, all concrete shrinks as it matures. The most shrinkage occurs when concrete is still new and fresh. As it matures, the rate of shrinkage declines. All this is to say that concrete never stops shrinking altogether. Over time, shrinkage can lead to cracking.

The extent to which shrinkage cracking takes place is influenced by a number of factors including the tensile strength of a concrete recipe, the amount of water the concrete retains, the amount of tension it is subject to, and the amount of creep taking place within the slab or structure.

So many influences dictate that is nearly impossible to prevent cracking fully. Even the best concrete jobs are subject to cracking over time. So if you have cracking concrete on your property, don’t sweat it. Cracks are to be expected. Nearly all of them can be fixed without harming the integrity of the structure.

If you are dealing with cracked concrete that is also sinking, feel welcome to contact us. We are Salt Lake City’s specialists in slab repair. We can raise that concrete to its original level and fill in the cracks while we are at it.

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Slab jacking is one way of affecting a concrete slab repair on a sinking patio, driveway, etc. It also works well to shore up sinking foundations and fixing sinking concrete steps. But if you don’t know how to fix a foundation or sinking slab, attempting to do it on your own could create bigger problems.

For all foundation and slab repair jobs in Salt Lake City, we recommend hiring a licensed contractor who employs trained, experienced technicians. Slab and foundation problems are nothing to fool around with. To drive home the point, here are three reasons slab jacking is not a good DIY project:

1. It Requires Specialized Knowledge

Slab jacking requires more specialized knowledge than some other trades. Why? Because there are multiple factors in play. You have the physics of the sinking concrete itself. You also have the underlying causes of the problem. If you do not know what is going on underneath the concrete in question, you will not know how to adequately fix it.

Slab repair via slab jacking is pretty simple in theory. In practice though, getting it right is anything but. Once you affect the repair, it is over and done with. Get it wrong and you are looking at digging up the entire slab and completely replacing it. Suffice it to say that slab jacking isn’t as forgiving as finishing drywall or painting.

2. It Requires Specialized Equipment

Beyond the knowledge required to do it right, slab jacking also requires specialized equipment. Right off the bat you are going to need a heavy-duty pump capable of handling the material you intend to force under the sinking slab. Such pumps don’t come cheaply. Obviously, a DIYer would rent one rather than purchasing one. But rental is not cheap, either.

You also need to know how to use the pump correctly and safely. Break the pump and you could be forced to pay for it. You just don’t need that kind of expense.

You will also need a concrete drill and the ability to use it safely. If you have never drilled through concrete before, it is quite an experience. It is not a job just anyone can do. You need to have considerable strength along with coordination and a bit of know-how.

It Requires Concrete Finishing

Finally, there is more to slab jacking than simply pumping material into the soil underneath the sinking slab. You have to finish the concrete once you are done leveling. That means filling the holes you drilled and leveling them. It is simple enough, but maybe not for someone who has never worked with concrete before.

One of our goals is to conceal the holes we drill as much as possible, so we have learned how to do it. We do not want to leave a concrete slab looking like it’s pockmarked. No job is perfect aesthetically, but we get pretty close. You might not be able to accomplish the same thing without extensive concrete experience.

There are a lot of projects DIYers can tackle by themselves. We support DIY maintenance and repairs when they are appropriate. But from our standpoint, slab jacking is not a good fit for DIY homeowners. If your property in Salt Lake City is suffering from sinking concrete, give us a shout. We will take care of it.

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Determining the viability of slab jacking requires understanding why the concrete is sinking. This is true whether you are talking a slab, steps, or foundation. Every sinking concrete structure is sinking for a reason. Generally speaking, the soil underneath is giving way. But that could be due to any number of reasons – each of which plays into determining whether or not slab jacking is appropriate.

Why Concrete Sinks

Concrete is a very heavy material. There is nothing new there. Understandably, heavy concrete requires adequate support from the soil underneath. If that soil is compromised, it can no longer provide the required support. The concrete sinks as a result.

Underlying soil can be compromised in a number of different ways. First is erosion. If water does not pass through soil at a slow and steady rate, it can erode areas through which it flows faster. Next is poor soil compaction. Soil that is not properly compacted before laying concrete can eventually settle. Lastly, there can be voids well below the surface that suddenly give way, causing soil closer to the surface to sink.

Understanding the Root Cause

Before we can advise on foundation or slab repair, we have to understand the root cause. As such, we may ask a customer several different questions that help us figure out what we are dealing with.

How quickly did the settling occur?

The speed at which a slab or concrete foundation settles gives us a clue as to what might be causing it. Extremely slow settling is generally not cause for alarm. On the other hand, if you were to notice significant settling occurring over just a few days or weeks, there may be a more serious problem under the surface.

How old is the house?

Older homes are more likely to experience sinking concrete due to building practices at the time of construction. Therefore, it is helpful for us to know how old the house is. We have a lot of older houses in Salt Lake City that were built before developers started paying close attention to soil quality.

Do you notice standing water after it rains?

Standing water after a rainstorm tells us a lot about a piece of property. A property may not be properly graded to facilitate appropriate runoff. It could be that downspouts are depositing too much water next to a driveway or slab. There could be any number of issues. Standing water gives us more clues.

What is your soil like?

Sometimes we ask customers if they know what kind of soil they have. Why? Because certain soil mixtures are more prone to sinking than others. Asking about soil types tells us what we might be looking at under the sinking slab or foundation. Then we will know better how to address it.

Slab jacking can be a long-term solution that lasts for as long as a customer owns his/her house. A sound repair lasting 10 to 20 years is not out of the question. Depending on the cause, slab jacking might only last 7 to 10 years. In extreme cases – for which we would not recommend slab jacking – you may get only five years or less out of it. The only way to know for sure is to have a professional come take a look.

The post Is Slab Jacking a Long-Term Solution to Sinking Concrete? appeared first on Concrete Raising Company.

Concrete slab repair may not seem like such a big deal when compared to replacing a roof or strengthening a weak foundation. In fact, structural repairs certainly are more important. And yet, a cracked or sinking concrete slab still puts downward pressure on the value of your home. It reduces value by creating a negative perception. The simple fact is that people do not like to see broken and sinking concrete. It causes them to worry.

Wondering What Else Might Be Wrong

Home buyers may not know all of the dirty little details about what causes concrete to sink and crack. But they do know enough to understand that there is some underlying issue going on. Seeing a sinking concrete slab during a home showing only causes potential buyers to wonder what else might be wrong with the property. This is obviously something to avoid.

A sinking slab may be nothing more than the result of underlying soil not being properly compacted before the slab was poured. The rest of the house, and its foundation, are in tip-top shape. Yet buyers might suspect something much worse is afoot; they might suspect the entire lot has settling problems.

As you might imagine, a sinking concrete slab can chase buyers away. That goes double for cracks in a foundation or concrete steps. How does this affect the value of your home? Through the simple law of supply and demand.

How Value Is Determined

Did you know that there is no static formula for determining the value of a home? Appraisers and home inspectors know the general guidelines, including the kinds of things that turn buyers off, and they also know how to compare homes against others in the neighborhood. But ultimately, your home is only worth what someone is willing to pay for it.

You could own the biggest and most beautiful mansion in town yet still have a property that is worthless to buyers. Let’s say an appraiser valued your home at $1.5 million. That is a paper value. If you list the home for a year and the best offer you get is $850,000, that is its value. You either take it or you take nothing at all, in which case you hold onto your property.

The Importance of Concrete Slab Repair

This understanding brings us back to the importance of concrete slab repair. If you have a cracked or sinking concrete slab, it is detracting from the value of your home. Reclaim that value by having the slab repaired. Remember that broken concrete gives potential buyers a poor impression of your property. Your goal is to increase the value by improving that perception.

Rest assured you do not have to spend a fortune to repair sinking concrete slabs or steps. The slab jacking process we utilize is fast, effective, and very affordable. Best of all, we can affect most repairs in just a couple of hours or so.

Remember, the true value of your home rests on perception. You can add value to your home by repairing any sinking and cracking concrete – be it slabs, steps, or the foundation. Concrete repairs improve perceptions which, in turn, increase value. It is no more complicated than that.

The post How Concrete Slab Repair Can Add Value to Your Home appeared first on Concrete Raising Company.

That solution is something known as ‘slab jacking’. Also known as ‘mud jacking’, it is an old technique that has been utilized in the U.S. for more than 100 years. Slab jacking in Salt Lake City is what we specialize in here at the Concrete Raising Company.

Slab Jacking 101

The premise of slab jacking is to avoid having to remove and replace sinking concrete by addressing what is behind the sinking. In every case, concrete sinks because the soil underneath has given way. There is a void underneath, a void that can be filled and pressurized in order to bring the concrete back to level. That is exactly what slab jacking accomplishes.

To fix a foundation or raise a concrete slab, we inject a specialized grout mixture into the void below the sinking structure. Once the void is full, we continue pumping the material in order to pressurize it. Under pressure, the grout acts like hydraulic fluid to push the concrete back up and into its original position.

The best part of slab jacking is that it isn’t limited exclusively to slabs. We can do more than driveways and sidewalks. We can raise concrete steps, foundations, and just about anything else made of concrete.

Why It is Better Than Replacement

It is awfully tempting to think that slab jacking is not as good as removal and replacement. After all, you are not getting a brand-new slab in the process. But concrete is concrete. Why put the money into removal and replacement when you can accomplish the same thing with slab jacking?

We submit that slab jacking is better in most cases. Here’s why:

• Cost – A typical jacking job is about one-third the cost of removal and replacement
• Speed – Raised concrete can be used immediately; there is no loss of use
• Waste – Slab jacking produces little waste. It also doesn’t leave a mess behind
• Weather – The process can be performed in any weather, so scheduling is not an issue
• Aesthetics – Slab jacking does not result in new and old concrete not matching aesthetically.

The final reason slab jacking is better in most cases is the fact that it actually addresses the underlying issue. This is most important. If you do not address the underlying soil and shore it up, you are not really solving the problem.

Why Concrete Sinks

As previously mentioned, concrete sinks because the soil underneath gives way. This could be due to poorly compacted soil, poor drainage, excess precipitation, or a number of other factors. At any rate, removal and replacement requires that the void be filled in with a proper material and compacted accordingly.

Unfortunately, even compacted soil can give way if the rest of the soil around it has not been compacted properly. Slab jacking, on the other hand, relies on a grout mixture that, under pressure, lifts up the sinking concrete to level. The mixture then hardens to create a permanent base for the concrete above.

If you have sinking concrete in Salt Lake City, you can choose to replace it or fix it. We urge you to consider raising that concrete by way of slab jacking. It is an old technique that stands the test of time, a technique that will save you money and save your concrete.

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