I want to build a home that sits on a crawlspace foundation. 2 Questions: How much space is needed between the bottom of the floor joists and the ground? Also, what size should the cement footing be if the stem walls will be built from standard concrete blocks? Thanks.
Kim ~ Stark County, OH
Hi Kim. Footing size for a home is determined by a number of factors other than just the size of the concrete block being used for the foundation. The primary concern is the type of soil your home is being constructed on and its capacity for bearing weight. I'm not sure where you're getting your home plans, but if it's from a local architect or drafter, they should have consulted with an engineer to determine the footing size needed for your house.
In most cases, a home with 8 inch concrete block walls on standard soils can get by with a footing that is 16 inches wide by 12 inches deep, but I have poured footings on many occasions that are wider and deeper due to the soil conditions that existed. If there is any question as to the characteristics of your soil, it is almost always money well spent to have an engineer take a look prior to starting your home. Remember that the footing supports the entire house and if it fails, the result is just about always a very costly repair.
Another issue to keep in mind is the type of veneer you have planned for the home. If you are considering brick or stone, the first several courses of block might need to be 12 inches wide to support the veneer. Larger block usually requires a wider footing.
The minimum distance from the ground to the bottom of your floor joists is normally 18 inches. However, if your home design calls for a lot of mechanicals such as drains lines and duct work in that area, your contractors will thank you if the space is a little higher.
Check with your local Stark County building inspection office to verify their requirements for the crawl space of a new foundation. While most counties use a version of one of the national building codes to establish their own requirements, it's not unusual for a few alterations to be made to better suit local conditions. Discovering that your new foundation doesn't pass local code can ruin a perfectly good day and cause a large budget over run just as you're getting started.