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I live in the NE and typically see houses with full basement. In some neigbhorhood pockets, there are a lot slab houses (built in the 50's) where the concrete floor is flush to the ground. I just saw a house listed for sale that says the foundation type is "piers" and that I haven't seen before.
It seems the bottom of the house is a foot or so off the ground. Is this the same as a house with crawlspace? It was built in 2004.... I thought to myself why the builder didn't just dig out and pour in a basement type foundation. Neighboring houses have basements.
I know that people don't value slab houses as much as traditional ones with a basement (slab houses tend to be slightly cheaper) . What about houses on Piers - would someone pay less if there are 2 identical houses but one has a basement and one is on piers?
Any pros/cons about this type of construction? I never lived in a place with a space between the floor and the ground. Would this not create a perfect enviroment for critters to sneak in and make a home?
A pier and post foundation generally would be referring to the elements of the foundation between the perimeter stem wall and footings of a raised foundation; the load on the span of the beams supporting the floor joists between the stem walls are also being carried by the posts, and the piers are the footings for those posts. I can't imagine a house having only a pier and post foundation without stem walls unless there is some sort of elaborate cross bracing that is providing the necessary shear values for the structure.
Maybe I am projecting the type of structural codes required where I am used to here in earthquake-prone California, but even when I see these types of foundation in the south in flood zones they seem to always have some perpendicular lengths of perimeter foundation to provide the necessary shear strength for the structure. A pier and post only foundation for me would raise some huge red flags, at least here in CA.
I'm not a structural engineer though so maybe some construction guys or architects have more insight to this than I.
A house on a crawl is usually just a matter of economics- it's definitely cheaper than a full fledged basement and somewhat cheaper/ or can be cheaper then a slab.
Other extreme cases could be an extremely high water table or bedrock.
Damon.
I've attached a photo here showing what a pier foundation is. Its quite common in many parts of the country. There is a perimeter foundation wall with piers (usually concrete blocks on a footing) in the middle to hold up the beams that hold up the floor joists.
They are sized and spaced according to the structural loads imposed on them. A beam (girder) is set on pressure treated lumber blocking (for a termite shield) and will run from one side of the foundation wall to the other. The floor joists are run on top of and perpendicular to the beam. Simple/smaller houses may have one set of piers with a beam running down the middle of the house. The floor joists span from the beam to the perimeter foundation wall.
In large or more complex homes, there may be several piers and beams. Some beams my intersect each other at a pier.
To the original post topic...
Yes this is a crawlspace home. Why they built it instead of a basement? No way of knowing unless you ask the builder. The original owner may not have wanted a basement. It might have been a cost issue. They might not have build a slab because the builder didn't like slabs.
There are pluses and negatives for all types of houses (bsmt/slab/crawl), and not always a clear answer of why one is built over the other.
The type of foundation in your particular area is usually governed by the Plasticity Index of the soil. If it's low, then a basement is acceptable. If it's high, the walls integrity of a basement may be an on going issue. Because you have all types of foundations in your area, I would say the PI is probably marginal for a basement. You can check with the Army Corps maps at any local colleges that has an engineering department for exact numbers. The Pier and Beam is the strongest of all of the different types. The piers, if installed correctly, do not move and foundation issues are non-existant. They perform well in high PI soils but they are not the cheapest. In your area, insulating the floor system is an issue as well as a moisture barrier. Slab on grade, if a post tension or cable design, is the cheapest and provides reasonable support for the house load. But, by design the slab floats with any changes in the soil volume due to water. Around here we have PI of 99 and that's pretty much considered unstable but builders can use a properly designed post tension slab and it works. The home owner is advised in closing papers that they are aware of the issue and that watering their foundation during dry times is a must to maintain their warranty. A steel slab comes in various forms from an FHA steel to common steel. They work great on stable soils but are expensive. Steel prices have risen 10 times in the decades I've been in the business. A basement may be good in stable soils and where the utilities are deep to keep from freezing during winter months. You can find a lot of info concerning foundations, insulations, building systems at buildingscience.com. Not all building systems are good for all parts of the country. We fight the heat here, you fight the cold. We fight the dry, you fight the moisture. Different areas require different building techniques.
Here's a linky on foundation repairs in regards to high PI soils. Expansive Soil Problems and Solutions
it depends on the soil. Where easy to do a slab with under reamig is very stable if done right at the time the slab is poured.Kind of a versio used for tall buiding fopr deacdes now;higher but worth the cost:IMO.
6x6 treated timbers would be considered "posts", not piers. They would still likely need the same size footing as piers.
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