Does Concrete Expand in the Summer and by How Much?

concrete expanding

Are you wondering if concrete expands in the summer? Curious about how concrete changes in the heat? In this article, I share what you need to know about your concrete in the summer.

Yes, concrete expands during the summer. Concrete can expand up to a half-inch per 100 feet of concrete. However, this number can vary drastically based on the heat and the environment. 

Concrete expansion is natural and expected during the summer. However, that doesn’t mean it can’t cause problems. Having a general understanding of what happens when concrete expands will give you the ability to respond to problems when they arise. 

Let’s jump in. 

How Does Concrete Expand in the Summer? 

Most materials expand in the heat. Heat causes molecules to move around faster, thus increasing the overall size of the material. 

Concrete is no different. In the summer, especially in high heat, it can noticeably expand. If your concrete was properly poured, with necessary relief measures in place, expansion isn’t an issue. 

However, if there’s a hitch in your concrete system, problems can and will arise. 

How Much Does Concrete Expand in the Summer? 

The standard formula for understanding concrete expansion involves a 100-degree F temperature swing. 

So, if your concrete temperature increases from zero degrees Fahrenheit to one-hundred degrees, then you will get an approximately 0.66-inch expansion, a little over a half-inch.  

Regardless of the amount of expansion, the main thing is to have protection in place to prevent damage. 

Outdoor concrete is the most likely to experience rapid temperature swings. You may wonder: will the concrete in my home expand in the summer? 

We’ll answer this below. 

Indoor and Outdoor Concrete in the Summer 

Don’t worry too much about indoor concrete expanding in the heat and contracting in the cold. Why? Simply because there are milder temperature swings indoors. 

Yes, you might go from 50 degrees to 70 degrees F, but that’s a much smaller amount than 0 to 100. 

Some places in the midwest United States have seen temperatures as low as negative 20 in the winter and over 100 in the Summer. These are the areas that are much more likely to undergo significant concrete expansion. 

If you’re curious about the specifics of thermal expansion and how it affects concrete, check out this video on understanding why bridges move. 

How to Prepare Your Concrete for Expansion 

Let’s go over several things to know regarding expanding concrete. If you haven’t poured your concrete yet, you’re in a good position, as you can build protection into the design.

However, even if you’re concrete has already been set, there are still steps you can take to prepare for expanding concrete. 

Here are several things you can do to prepare for concrete expansion: 

  • Talk with your builder before they pour concrete 
  • Control Joints
  • Expansion Joints 

Talk with Your Concrete Company 

If you hired someone to set your concrete for you, then ask them about how they will account for the expansion of the concrete. 

They will likely tell you several things. First, they will mention you want to pour concrete during optimal conditions to get the most durable set. 

Second, they’ll mention control joints, areas that actually encourage a controlled crack. 

Finally, your concrete company with likely mention expansion joints, a gap that allows the concrete room to move. 

We’ll explore these two types of joints in the next section. 

Control Joints in Concrete 

There’s a saying around concrete that goes like this: there’s cracked concrete, and then concrete that will crack. 

The control joint is all about controlling those cracks. By deciding where the concrete will crack, you will prevent ugly separation in your concrete and have more manageable repairs. 

How does a control joint work? A control joint is a groove that is placed in the concrete before it fully hardens. When trying to imagine how a control joint works, think about a Hershey’s chocolate bar and how the chocolate has thin areas that allow you to break off a piece. 

Typically, the control joint groove is about one-quarter of the total thickness of the concrete. So if you have a four-inch slab of concrete, you would get a one-inch control joint. 

The placement of these control joints is specific – you don’t want haphazard lines running all over your driveway. 

Expansion Joints for Concrete 

Expansion joints are different than control joints. They allow space for the concrete to expand. If you walk out and look at your driveway, you’ll almost always find an expansion joint where the driveway meets the garage. 

An expansion joint is a total separation from two slabs of concrete. Most expansion joints are pre-planned and built into the concrete pour. 

After the expansion joint has been placed, homeowners will often choose to fill in the gap with a pliable substance. Filling in your expansion joints prevents ice build-up in the winter but still allows for concrete movement. 

If you’re getting ready to pour some new concrete, be sure to have the right expansion joints in place. 

Is There Any Way to Prevent Concrete from Cracking During the Summer? 

Concrete will expand when exposed to heat. Trying to restrict the expansion of concrete will not lead to fruitful results.

However, if you can control the temperature, you could control the level of expansion and possibly reduce cracking. If you live in an area with large temperature swings, here are a few ideas to protect your concrete driveway from the elements.

Here are a few ways to protect your driveway from cracking:

  • Beware of plants 
  • Seal your concrete  
  • Build it properly

Let’s look at these things in more depth. 

Beware of Plants Around Your Concrete Driveway or Sidewalk

Plants are a beautiful thing. Trees, flowers, grass, we all love them. However, like all good things, if you let plants get out of hand, they cause problems. 

Especially around concrete. 

We’ve all walked on a sidewalk that is being lifted from the ground by a tree root. If you’re looking for a place to plant a tree, keep them well away from concrete structures around your home. 

Also, if you have a small tree growing near a driveway, see if there’s a way you could safely move the tree to a better location. 

Though tree roots can be a problem, tree shade is another issue. When half of your driveway is covered in the shade, it causes the shaded portion to expand at a different rate than the rest of the concrete. In this instance, maybe you could trim the tree or perhaps find a way to shade the other portion of the concrete. 

Seal Your Concrete 

Sealing your concrete is a good idea in principle, but in practice, it can be tricky. If you take the time to seal your concrete properly, then you’ll be on your way to protecting it from the elements. 

There are two main types of concrete sealer. One type rests on the surface of the concrete, and the other penetrates the concrete. 

Both will protect your concrete; however, if you apply a sealant on the surface improperly, you risk messing up the concrete’s moisture regulation, leading to more problems. 

Pour Your Concrete Properly 

An ounce of prevention is worth a pound of cure. That saying has never been more true when it comes to concrete. 

If you don’t have control joints, expansion joint, adequate thickness, rebar, and proper slope, you’re fighting an uphill battle. 

In other words, if the concrete was incorrectly placed and poured, it’s very difficult to keep it from cracking. 

This is why it’s essential to do your research, talk to the construction manager, and ask the right questions. 

Can You Repair Crack in Concrete? 

If you have a crack in your concrete somewhere, do not be alarmed. This is a common issue, and it doesn’t mean your driveway is about to explode. 

However, if you don’t attend to the crack, you could have bigger problems in the future. 

Here are a few things to keep in mind when repairing a crack in concrete

  • Use a concrete gap filling 
  • Be sure to clean out the area 
  • Don’t wait on bigger repairs 

Let’s look at these a little closer. 

Concrete Gap Filler for Cracks 

There are several types of concrete filler for cracks. You want to assess the size of the gap that needs to be filled and then match that with the concrete fill. 

It’s not recommended to mix up a bag of old concrete and use that as filler. This will not have the adhesive effect you want and will likely require repair in the future. 

Some concrete gap fillers come in a tube, like caulk. For especially large gaps, other fillers come in a mortar that needs to be applied and smoothed. 

Don’t Wait to Make Bigger Repairs 

Sometimes, you might need to hack out a section of the driveway or sidewalk and completely re-pour the concrete. Some concrete failures are too big to repair. 

While cracks on a driveway are mostly cosmetic, yet if you have large cracks in your home’s foundation, I suggest you have it addressed immediately. 

Final Words on Concrete Expansion in the Summer 

Concrete will expand in the summer. However, there are several techniques you can use to prevent damage from expansion. 

If your concrete cracks, all hope isn’t lost. Clean out the crack and repair it as soon as possible; otherwise, you’ll end up with more serious issues.