What caused houses to go from having crawl spaces underneath to being on a concrete slab, no space underneath?
In: Engineering
slab houses are super cheap to build. They became very popular in post-war mid-century modern style houses like the ranch. Building during that time needed to be fast and inexpensive. It also had to become more efficient in the use of materials as the demand for post-war housing strained the supply of building materials. You still see basements in the In the North and North East but outside of freezing climates basements become and unnecessary expense.
Slab-on-grade is the cheapest, simply put.
Most houses are built by larger real estate developers these days, rather than smaller home builders, and profits are the #1 concern.
There’s probably a few different reasons, though I’m no expert or house-builder. First, maintenance on utilities running through a crawl space has reduced over time, so we typically don’t need constant access to the pipes anymore. Second, crawl spaces lose a bit of heat, but more cold cuz cold air sinks. Concrete loses less either way, but the proliferation of AC has probably affected it. Third, you don’t have to worry about concrete rotting or housing vermin. And lastly, building codes in some areas probably make it more worthwhile to have concrete foundations, or outright ban crawl spaces for new housing.
Depending on where you are, it may also just be easier, because of the underlying ground. Digging through shallow rock is expensive and time-consuming.
There are also cultural effects. Most houses in South Africa do not have extensive basements at all, for example.
The availability of durable rigid foam insulation makes slab on grade foundations easier to protect from frost heaving in places where the ground freezes.
The primary purpose of a deep foundation is to get below the frost line. But you can also protect a shallower foundation by laying rigid foam around the outside perimeter.
Hmm, I live in the Northwest United States. I’m no expert, but I can’t think of a house I’ve seen that didn’t have a crawlspace. (Unless it had a basement.) Perhaps this is a regional difference. For example, your region may be more prone to mold (humidity is higher), hurricanes and flooding, earthquakes, etc..
Also the type of dirt and susceptibility to flooding is also a factor to having a basement or not.
Latest Answers