The foundation of your house can significantly impact its structural integrity. The concrete of a slab foundation usually is 4″ to 6″ thick in the center. For drainage or as a cushion, the concrete slab is frequently put atop a layer of sand. Crawlspaces are not available in slab-built homes, and there is no space beneath the floor. First, however, consider some problems with slab homes if you’re thinking about building or buying a home on a concrete slab [1].
In the early 1900s, concrete slab foundation homes became popular, and their popularity grew. They were famous for a reason, but they tended to make other home systems, such as plumbing, more challenging to maintain and operate.
Today, 54 percent of new single-family houses are built on slabs, implying that the same plumbing and foundation issues persist. Understanding the causes and symptoms of damage can assist contractors and homeowners avoid problems with slab homes if they emerge. [2]
Buying a House on a Concrete Slab
Because certain locations have shallow water tables, some residences are built on a slab instead of a crawlspace or basement. First, the concrete is poured all at once onto the ground. Next, post-tension cables or steel rods (also known as rebar) are used in some foundations to ensure that the slab can support the weight of the house. [3]
After that, the home is built on top of the concrete foundation. Slab foundations are more frequent in warm-climate states like Florida. If you build a slab house in cold climate, the ground is likely to freeze and damage the foundation.
How to heat a slab home
An electric heating cable can be inserted into the concrete slab as it is poured for new-construction residences. [5]
However, the most typical application is an in-floor heating system built between the completed concrete slab and the floor above. For example, in a slab bathroom, the concrete subfloor would be covered with a layer of cork or synthetic cork underlayment, followed by the electrical heating element, and finally, the flooring substrate. The heating element is protected by the underlayment from the slab beneath, which would otherwise dissipate the system’s heat.
How to build a house on a slab
Slab foundations serve as the basis for new homes, garages, sheds, gazebos, and other structures. You’ll need a basic understanding of construction to lay such a foundation. The duration of your project and the stability of your structure will be determined by the quality of your slab foundation. To make one, you’ll need a lot of patience, expertise, and skills. The following are some fundamental measures to take.
Step 1: Make a project plan.
Determine the slab foundation’s width, length, and thickness.
Step 2: Get the Ground Ready
a) Remove any obstructions from the ground, such as sticks, pebbles, and rubbish.
b) Use 2-inch by 12-inch planks to create a frame around the area where the slab will be poured.
c) Dig the footings
d) Level the ground within the form
e) Compact the soil as much as possible by tamping it down.
f) Reinforce the footing using rebar
Step 3: Fill the Footer with Cement
To make the cement, combine mortar and sand according to the manufacturer’s instructions. Pour enough cement into the footers to cover the foundation’s entire perimeter. Allow the cement to dry for a while.
Step 4: Lay the Groundwork
Wrap 2×4-inch or 2×6-inch wooden planks around the entire circumference to lay the foundation. Ensure that the wooden boards are of equal lengths and widths. They’ll support the concrete you’ll use to build the foundation.
Problems with Slab Homes
Because slab foundations are cost-effective and well-suited to most soil characteristics, they are commonly used in household constructions. These foundations, however, are not without flaws. Poor planning during the construction phase causes many slab foundation issues. The problems can also develop over time due to age and other related issues. Common problems with slab homes are outlined below.
Foundation Upheavals
When the soil beneath the slab swells, the slab can heave. The soil absorbs water and expands, thereby pushing up against the concrete slab above. A shoddy foundation can also cause slab upheaval. Roots growing beneath the foundation might push on the concrete, causing the slab to shift. This is particularly common during droughts when thirsty roots seek water. To check if your slab has an upheaval problem, look for uneven floors and walls and slanted worktops or floors.
Cracks in the foundation
Slab fractures are a common occurrence. The foundation may crack if it heaves. The problem can also be caused by settling or shifting foundations. The slab may crack if the soil beneath the foundation swells and pushes on it. The concrete may break when it settles into the gap as the slab sinks due to the ground’s inability to sustain it.
If you notice slab cracks, measure them to see how severe they are. Contact a foundation repair specialist if the fissures are more extensive than 1/16 inch. Foundation fissures might cause water leakage or insect infestation.
Shifting foundation
If your foundation has piers, they may shift, forcing it to turn. This can happen if the piers aren’t properly built. The piers move due to changes in the soil or moisture content of the earth. A slab foundation might slide or shift without piers as the soil around your property swells or shifts. If you notice bulging floorboards, stuck doors, or internal fissures, your foundation may be shifting.
Foundation Settlement
Every home settles with time; it’s a natural component of the aging process. Rapid or uneven slab settlement, on the other hand, might cause significant foundation issues. Due to erosion or soil contraction, voids may appear beneath your property. This is because it shrinks and falls away when the earth dries out, leaving gaps beneath your foundation. Erosion can also remove soil from beneath your home, producing cracks.
Earthquakes or sinkholes can also cause settlement near your property. Consult a specialist if you see fractures on the exterior of your home, slanted flooring, cracks on the ceiling or floor and the walls, or stuck windows or doors.
Improper Construction
A poorly poured foundation can cause slab difficulties. If the dirt beneath the foundation is not compacted correctly, it will settle quickly, causing foundation and structural problems. In addition, if the foundation is improperly planned or the concrete is improperly mixed, it may crack or develop other issues that compromise structural stability.
Plumbing problems
It is necessary to cut through concrete for workers to reach the damaged pipes if there is a sewer leak. This makes it difficult to access and fix such pipes. In addition, it takes time and money to demolish concrete to get to a broken water line.
Concrete is also a porous surface. While water can move through the pores and tunnels of concrete, it can eventually compromise the material’s integrity.
Wet concrete retains moisture, allowing mold to grow and emit nasty smells. If a mold infestation occurs, it will require more time and money to remediate, and it could jeopardize the homeowner’s entire foundation.
Signs of Plumbing Problems
Although specific symptoms of plumbing issues aren’t always visible, knowing what to check for is important. Homeowners may discover a sudden increase in their water costs before any visible red flags appear. An abrupt decrease in water pressure is another symptom. Some folks may even hear rushing water under their floor if the leak is severe. Various signs of plumbing issues include:
- Water marks on the foundation floor.
- Water that has pooled in depressions in the yard.
- There appears to be foundation damage.
- On the foundation floor, there are puddles.
- Cracks in the foundation or walls of a building.
- There are some soft patches on the floor.
- Mildew scents or visible manifestations of mildew.
These are symptoms that contractors and homeowners should be aware of. Contractors should encourage their clients to keep an eye on the region after they fix the foundation of a concrete slab home in the weeks following the repairs.
When should you repair your concrete slab?
Concrete slab degradation can be caused by various factors, including soil, climate, leaking pipes, and insufficient drainage from the foundation; it’s always a good idea to look for warning signs. Here are some slab foundation problems signs:
- a) Fractures in the walls or on the floor
Horizontal fractures in your building’s external brick are a solid sign that the foundation has weakened. Horizontal cracks are more noticeable than vertical fractures because they can indicate significant tension along the perimeter of your home’s foundation. Because vertical cracks in drywall go in the same direction, they are usually not a symptom of a problem.
- a) Settlement of the foundation
The term “foundation settlement” describes how the foundation of a concrete slab sinks more than it should. Your home’s slope is natural, but it could mean your foundation is sinking if it’s becoming worse.
- b) Upheaval
It’s usually a warning that the foundation is shaky when you notice your house sliding upward. Foundation upheaval is the opposite of foundation settling because it rises rather than sinks deeper.
How to Solve Slab Foundation Problems
It’s crucial that you look out for signs of foundation deterioration. Take immediate action if you see any of the signs mentioned above. If you wait, the condition will worsen, necessitating a more costly repair. Conversely, you’ll save money if you detect and fix a foundation problem early.
Common solutions to problems with slab homes are use of:
- Resistance/Push Piers
- Helical Piers
- Drilled Concrete Piers
- Poly Foam Injection
These technologies elevate and level your slab, preventing structural harm to your home. Underpinning, which stabilizes and lifts the concrete slab foundation, is used to install the piers beneath the foundation. These piers are long-lasting and durable, and they function with a variety of constructions.
Polyurethane foam injection can help if you have a sunken, uneven driveway, sidewalk, or other types of concrete slab. Injecting a foam substance beneath the slab to fill in subsurface voids and elevate the slab is known as polyfoam injection.
In some cases, foundation replacement is also required. For example, if your home or business premises has severe slab problems, the best choice may be to completely replace the foundation with a new slab.
Michael Davis is a heating & plumbing expert who currently works as independent contractor in SC. He also writes for Plumbertip.
For almost 10 years he worked on various plumbing tasks across South Carolina.
