Slab foundation, otherwise known as concrete foundation, is one of the two main types of residential foundations found in the Fort Worth, TX area. The other type of foundation is Pier and Beam, but we will be discussing the slab foundation here. In this page, we will discuss the history of concrete foundation, how it’s made, and some advantages and disadvantages of this foundation. I hope to inform you about your home’s slab foundation and also how to reach out to us if you need foundation repair.
History of Slab Foundation
Slab foundation in residential homes began dominating the preferred method of foundation in the 1950s in areas where temperature was relatively warm year round. The reason why weather or temperature is a factor in deciding to choose slab foundation is due to concrete’s properties. Slab concrete is very strong and has a high efficiency of compression. This means that it can hold a ton of weight above it, thus making it very popular.
Another property of slab concrete that most people don’t think about is it’s weak tensile strength. Basically, slab concrete can be pulled apart much easier than it can be crushed. Think of it like the opposite of a chinese finger trap which is hard to pull apart, but can’t hold any weight. Because of this property in slab foundation, rebar, which is reinforced steel bars (get it?) are usually placed within the concrete slabs and more importantly, the concrete perimeter walls that will bear the largest weight of residential homes.
So, now you understand a little more about slab concrete foundation. Let’s take a look at how it’s made.
How Slab Foundation is made
Slab foundation is made in several steps. From analyzing the soil to layering the concrete slab to adding rebar and formwork to pour the concrete, slab building takes time and professional experience.
Preparing the soil
The first step is grading the soil.“Grading” is just a fancy word for analyzing. This is usually done by a soil specialist using a sieve or hydrometer which are tools to figure out exactly what type of soil you have. This is extremely important for your foundation because if the soil is not the correct grade, soil shifting can occur and can cause foundation damage.
For a slab foundation, you want to have soil that’s graded well for your house’s foundation. A soil that can withstand your home’s concrete slab foundation is ideal. If this is not properly done and compacted in a uniform way, the soil in your home can experience shifting and settling which can damage your foundation.
This is a nightmare for homeowners and part of the reason why Optimum Foundation Repair is a trusted source for foundation repair in the Fort Worth, TX area. If your foundation is experiencing any signs of foundation damage, call us now at (817) 934-1381 or fill out our contact form to have a professional come inspect your home for free.
The Formwork
The second step after grading the soil (see you at least learned a new word today) is to prepare the area for the concrete using formwork. Formwork is the temporary or permanent perimeter or mold into which your home’s concrete slab will be poured. The formwork will give the concrete slab its form. The average height of a residential home’s concrete slab floor is between 4-8 inches. It also has rebar or post-tension(PT) cable reinforcement to compensate for the weak tensile strength we described earlier.
The slab concrete edges and inner walls as well should always be reinforced with rebar or PT cables(which are steel cables) since the load on the perimeter will primarily rest on this slab. Consequently, the perimeter and wall slab will be more influenced by shifting soil. That is why you will often see vertical cracks riding corners or adjacent to walls. By now you may have realized that shifting soil is a major problem causing foundation damage in Fort Worth, TX. If you would like to know more about shifting soil and what causes it, check out our section on what causes shifting soil.
Protecting your slab
Moving forward, the slab floor edges are always thicker. Most places require a minimum of 12 inches in thickness, but some are as large as 36 inches. ‘Footing’ is another word for these. There are several types of footing(See images below. Depending on the type of footing your foundation has, your home might be more susceptible to foundation damage. External forces such as moisture can greatly affect your foundation, especially your rebar.
This is why it is very important to have a concrete cover for your foundation. A concrete cover is exactly that, a covering of concrete. Basically, the rebar inside the foundation has the potential to rust. When some rebar rusts, it’s diameter expands. If this happens to a great enough extent, your home’s foundation could begin to destroy itself.
Yes, the very thing you added to prevent your concrete foundation from cracking will break it. Why? Because as the diameter of the rebar inside your foundation slab increases, the pressure on the tensile strength of the concrete will crack it. It’s like a boiled egg cracking it’s shell. The egg grows in size until the egg shell starts to crack. This is why concrete covers are important. The concrete cover is the distance between the ends of the rebar to the soil or outside of the foundation. The concrete cover keeps moisture from reaching the rebar and promotes longevity in foundation health.
One step that was not mentioned in this article was the layering for the slab concrete such as a moisture prevention layer placed below the concrete slab. This layer prevents moisture from getting inside cracking the foundation from below. This added layer gives you time to repair your foundation before it becomes a larger problem.
When to contact a specialist
If you are noticing cracks in your floor or on your outside concrete perimeter, give us a call immediately. You might not need foundation repair, but our free inspection will give you peace of mind. Now, let’s look into some of the advantages and disadvantages of a slab foundation.
Advantages of Slab Foundation
There are several advantages of a concrete slab foundation. Below are some of the major advantages. Feel free to use this list to further understand how your home’s slab foundation helps you and your home.
- Slab foundation does not have a crawl space underneath like pier and beam foundation. This reduces termite problems affecting wooden beams and joists found in pier and beam foundations.
- A Slab foundation does not deteriorate. Wooden beams and joists deteriorate over time. Moisture in the crawl space can create less than ideal environments for beams to rot, grow mildew, or even collapse.
- A slab foundation is less expensive to make and usually much faster. This means your house will be less pricey. If you’re a builder, it means less time invested into building the house.
- A slab foundation is durable! Extreme weather will not affect your slab foundation. Pier and beam foundation, however, that’s a different story.
- You can stain or customize your slab foundation. Yes, you can design right on your slab foundation and even stain it to a beautiful color.
Disadvantages of Slab Foundation
There are few disadvantages to a concrete foundation, but they are worth noting. Below are some of the major disadvantages of the slab foundation.
- Slab foundation does not have a crawl space. Because there is no crawl space, plumbing remodeling or fixes will have to jackhammer into your slab.
- You will also have to place all your heating and AC units somewhere in the house when they would normally be under the house. Ductwork will have to tear into your walls.
- Slab foundation cracks. If the soil starts to settle or shift, your slab could start to crack. There are actually several reasons why a slab foundation would crack, but in Fort Worth, TX, this is the main reason. And not only is this ugly, but this could mean costly repairs.
- Slab foundation has much poorer insulation than pier and beam. Insulation under the concrete slab is a possibility, but in general slab foundation has poor insulation.
Conclusion
To sum it up, a slab concrete foundation is a great way to create a lasting foundation for your home. It has many benefits with few drawbacks. This is why it is a preferred method of building a foundation in temperate climates. However, when there is a problem, foundation repair NEEDS to immediately done.
At Optimum Foundation Repair, we offer free foundation inspections that quote you the price and inform you exactly what is going on. Call us now at (817) 934-1381 or fill out our contact form below and get started today on ensuring your home’s future.
