The cost of a slab versus a raised foundation varies based on the size of your home, the design and where you live. You can save money with a concrete slab, but a crawl space or basement may be worth the extra cost.
A monolithic concrete slab will typically cost $4,500 to $12,000, which is cheaper than either a crawl space or a basement. It has stronger floors without rot, sagging or creaking. These homes are faster to build, as well. But they are best for climates that don’t have much freezing and thawing in the soil. Stem concrete slab cost more, $7,000 to a high of $21,000, but it includes concrete reinforced with rebar, poured into the ground. These are better, and much more typical, in cold climates. They are still generally the cheapest way to go up front, when you’re building your house.
Slab foundations on average are about $10,000 cheaper than most crawl spaces. Slabs are much cheaper if a crawl space or basement must be carved out of solid rock, which can be very expensive. Slab foundations make it less likely that radon gas will leak into the house. They protect a home from termites and other insects.
But, with concrete slabs, it’s difficult to get to plumbing, electrical wires and duct work built beneath the slab, making for costly repairs. The risk of flooding is higher because these homes sit on the ground. They are not as comfortable to walk on, and some people find them unattractive because there is no break between the house and the ground.
The raised foundation makes it easier to access plumbing and wiring beneath the home. This will mean cheaper costs in the future. Also, floors are made of wood, which is softer and more comfortable to walk on.
But they cost more. Costs can range up to $25,000. These take longer to build, but they protect the house against flooding. Crawl spaces require about the same amount of time as basements to build. A crawl space, unlike a basement, can also be conducive to water and humidity buildup, causing rot and fungus to grow. Also, termites and other wildlife can infest the area. Crawl spaces, like concrete slabs, offer your home little to no protection against bad weather.
There are steps you can take to prevent some of these problems. You can close off the crawl space or install ventilation areas. You can also put in insulation and vapor barriers, or even a crawl space humidifier, for $70 to $1,300.
These are the most expensive, but offer more return on your investment. A new basement averages about $18,000 to $30,000. Excavation and grading are some of the highest expenses. Factors include cinder block versus poured concrete, drainage systems, insulation, sealers and waterproofing.
Cinder block basements can leak as they age. Poured concrete walls offer better structural integrity and moisture protection.
Also, consider the type of outside entrance you want. Should there be an outside entrance, which can be handier, or only an inside entrance, which is less expensive? Building into a hill can make an outside entrance cheaper, and allow you space for windows.
Basements are good ways to anchor a property to the ground. If you live in an area with a frost line, basements help maintain the integrity of the foundation over time.
Leaving the basement unfinished is cheaper. Refinishing your basement typically costs $6,500 to $18,500.
Basements also offer square footage for less money, since basement square footage costs less than other parts of the home.They need less heating and cooling since the ground acts as an insulator.
Besides the cost, disadvantages include rooms with little or no natural light and potential flooding. To combat this, have a good drainage system, or ensure that the house is built with a natural path for drainage.