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Understanding Foundation Types and the Problems They Face

Written by admin on . Posted in Homeowners Blog.

When it comes to foundation health, not all types are created equal. Each has unique characteristics, and each comes with its own set of challenges. Whether you’re buying an older home, planning repairs, or just want to understand what’s under your feet, this guide from the National Foundation Repair Association breaks down the most common foundation types and what issues to watch for.

Foundation Types

Brick Foundations

Brick foundations are among the oldest and most fragile types. While charming in historic homes, they come with several vulnerabilities:

  • Bricks are brittle and degrade over time: Peeling, cracking, and crumbling is common.
  • Mortar joints are weak points: As mortar deteriorates, it compromises the structural bond.
  • Prone to bowing: The number of joints creates natural stress points, leading to inward wall movement.
  • No waterproofing system: One of the older foundation types, these foundations predate modern drainage and sealing methods.
  • Often built without footings: This makes them especially vulnerable to settlement and shifting.

Cinder Block Foundations

Once a popular alternative to traditional block, cinder blocks are mostly a thing of the past.

  • Made from coal ash (cinder) and cement: Lightweight and inexpensive, they were widely used in the early 1900s.
  • Weak and outdated: Prone to cracking, bowing, and buckling. Often costly to repair.
  • Limited structural strength: These blocks are rarely used today and haven’t been mass-produced since 1947.

CMU (Concrete Masonry Unit) Block Foundations

Modern CMU blocks replaced cinder blocks after World War II and remain widely used today.

  • Made with fly ash, slag, or cement: These are environmentally safer and much stronger than cinder blocks.
  • Higher durability: These blocks offer improved pressure resistance and structural integrity.
  • Common in new builds: A reliable, long-lasting option when installed and maintained properly.

Stone Foundations

Stone foundations (like limestone, sandstone, fieldstone, and rubble) are one of the most beautiful foundation types, but are often problematic due to age.

  • Mortar erosion: Weakened joints lead to structural compromise.
  • Water intrusion is common: Especially through deteriorated joints or cracks.
  • Surface coating (parging) degrades: Parging wears away with water exposure.
  • Bowing and shifting walls: Due to the volume of weak points.
  • Cracked stones and moss growth: Signs of long-term moisture damage.
  • Stone and mortar breakdown: Foundations may literally crumble into sand over time.

Poured Concrete Foundations

Modern and strong, poured foundations are formed on-site by pouring concrete into molds.

Advantages of Poured Concrete Foundations

  • Faster to build than block foundations
  • Better waterproofing with fewer joints
  • Higher lateral strength resists soil and water pressure
  • Durable and relatively low-maintenance

Drawbacks of Poured Concrete Foundations

  • Prone to spalling if not cured properly
  • Higher installation cost
  • Difficult and expensive to transport concrete to some job sites
  • Susceptible to cracking, leaking, and settling if not installed correctly
  • Low insulation value (R-value below 3)

Reinforced vs. Unreinforced Concrete

The key difference? Steel rebar or Carbon Fiber staples/rods.

  • Reinforced concrete: Includes rebar or carbon fiber reinforcement, making it more resistant to bending, tension, and lateral pressure.
  • Unreinforced concrete: Can be effective for some applications but is far less resilient under stress.
  • Reinforced foundations: Ideal in areas prone to soil movement, high winds, or seismic activity.

Slab-on-Grade Foundations

Common in warmer climates, slab-on-grade homes are built directly on a concrete slab.

Advantages of Slab-on-Grade Foundations

  • Fast and cost-effective to build
  • Less risk of basement flooding or radon intrusion
  • Fewer pest problems
  • Energy efficient for cooling

Drawbacks of Slab-on-Grade Foundations

  • HVAC ductwork is harder to access and must be insulated
  • Takes up valuable space indoors
  • More prone to movement due to expansive soils
  • Vulnerable to water intrusion if exterior grading is poor

Crawlspace Foundations

Crawlspaces are shallow foundations that slightly elevate the home, typically 1.5 to 3 feet above ground level. This creates a narrow, accessible space beneath the house, which is used to house essential utilities like plumbing, electrical wiring, ductwork, insulation, and HVAC systems. In some homes, this area also serves as limited storage.

Advantages of Crawlspace Foundations

  • Lower construction costs compared to full basements
  • Warmer floors than slab-on-grade homes, due to air circulation beneath the home
  • Easier access to mechanical systems for maintenance and repairs
  • Potential storage space, especially when well-maintained and dry

Drawbacks of Crawlspace Foundations

  • Moisture concerns are common, even with modern vapor barriers. Persistent dampness can lead to mold, mildew, and fungal growth, posing health risks and damaging wood framing
  • Air quality issues due to the Stack Effect. As air naturally rises through the home, it pulls up air from the crawlspace. With open vents (still required by many building codes), up to 50% of the air in your living space may originate from the crawlspace. If that space is damp or contaminated, those same conditions affect the air you breathe inside your home

foundation problems, types of foundations