Beginner Guide to Foundation Types
There are five common foundation types homes typically have. I will break down the basics of the five categories below with the pros and cons of each type and whether they are a potential harbinger of doom for home health.
Slab On Grade
A slab-on-grade foundation is concrete poured on graded ground and may have an aggregate layer too. The concrete is about six inches deep with a thicker edge to hold up better against the weight of the home. Slabs are a cost-effective and easy foundation choice. A slab is a solid choice from the perspective of Building Biology and mold risk as long as they are checked for adequate curing before further building begins.
Slabs are a safe choice if done right. Your plumbing goes under the slab, and if you ever have a leak: Danger, Will Robinson. It’s a next-level problem to fix. But the pipes shouldn’t fail inside the slab once the concrete cures except when there are corrosion concerns. A slab foundation gets two out of five scythes on the death trap rating.
Crawl Space
Crawl spaces are a cornucopia of delight if a Petri dish of fresh-grown biohazards sounds like a good time. Older homes have unsealed crawl spaces, usually with the ground exposed, and may even have HVAC ducts under the house if the design is super cringe. Most new homes have what the industry calls sealed crawl spaces, but the typical standard misses the mark, and they almost always fail.
One of the many issues with this type of foundation is damp, unconditioned air. The safest crawl space is fully sealed (encrapsulations abound) and conditioned (dry and temperature controlled). Crawl space air will find a way indoors from the stack effect and lives rent-free through cracks or openings in the building. Crawl spaces of any kind are not recommended and rate a five out of five scythes on the death trap rating.
Basement
Adding an underground level to a home is like buying something late at night but forgetting why. One drink too many made it sound like a good idea at the time. Unfortunately, returns and exchanges are not available for a foundation. Well-built basements exist but they’re still below ground.
Also, this is never a safe choice in hot and humid climates or for dense soils that are slow to dry. There should be enough moisture management measures to protect against rising damp and water-logged wall and insulation materials. Carpet in a basement will always to you dirty, as well as other materials that take in water but cannot properly dry out in time. A portable dehumidifier should be on continually in all cases and climates. A basement rates four out of five scythes on the death trap rating.
Pier and Anchor
This foundation type is also known as a pier or pier and beam foundation. The height of this foundation is similar to a sealed crawl space, but with all sides open- air. Sometimes one side may need a wall to direct water depending on the home site drainage. But the key is ample airflow and access.
The building envelope stays away from the ground with this foundation which is a big plus. The bottom side of the home should be weatherproof and built as another wall. Plumbing and other components are most accessible with a pier and anchor foundation. But the cost is higher than a slab foundation and is not a popular choice today. Pier foundations rate two out of five scythes on the death trap rating.
Coastal Pile
Pile foundations are deep and use reinforced concrete, steel, or timber for resistive soil types. A foundation piles when its depth is three times its breadth. The higher the foundation, the more elements like wind affect the design differently. You also have to consider sand is not a hostile “soil” and building on it at a great height creates a lot of problems that needs solving.
If someone is building or living on the coast they’re assuming the risk and responsibility it will take for constant upkeep against the harsh climate conditions. A coastal pile foundation rates three out of five scythes on the death trap rating.
There are no perfect foundations, only the one that makes the most sense for you. But this is an ideal scenario, and plenty of situations are less than ideal unless you get lucky. There are genuine obstacles that need changes beyond these. Privilege, social and economic status, and racism are all factors in the problem. Everyone deserves to be at ease in their environment. Get the guidance right for you. Start on your healthier home today.