Crawl Space vs. Concrete Foundation

[southernlady5464]

If you live in an area where radon is a concern, I would reconsider that basement or crawl space. EPA Map of Radon Zones | Radon | Indoor Air Quality | Air | US EPA Liz

[Oscar88]

Hi friends, fellow home owners. I hope you all will allow me to pick you brains. I bought my first home in South Florida, built in 57 about two years ago. It has a crawl space under most of the house, seems additions where built around the house in the back and also closed off a car port all before my time which obviously stops the air flow from front to back, etc.. When I had the house inspected the inspector told me the wood under the house was in great shape, does appear to be some sort of old strong Pine, I had to remove a soffit wall for a kitchen renovation and that wood in the was wall was some of the strongest stuff I have ever seen, so the house seems to have been built the way they no longer build them, right.. Anyhow, the point here is I worry about the humidity in the crawl space if any and I have turned to a few on line sources which seem to contradict each other on fans vs. sealing, vs. whatever... Anyone have any suggestions or experiences with this same issue. Remember I'm in South Florida, Miami Dade where the water table is high and so is the humidity level..

[spacelord75]

I am in Atlanta and slope of my land leads to a decent amount of water intrusion under my house in the crawl, along with high water table. I, too, have read all the reports on crawl space encapsulation and finally pulled the trigger last year to seal it off. I mainly did it because I had new hardwoods that were already cupping due to the moisture transference from the humid crawl up through to the air conditioned main floor (it was previously a vented crawl with 6mil plastic strewn about the floor, also already had perimeter drain and sump pump). The guys I hired after extensive research on companies graded the crawl, re-did part of the perimeter drain that was improperly sloped, rolled out 20mil vapor barrier (used a mastic and tape to close off seams) up to within 6" of foundation wall top, seal the vents and put in a heavy duty dehumidifier. I have since been down to the crawl on numerous occasions after rain (bone dry) and with the early arrival of summer here already to measure the humidity and it is staying at 40-50%. My floors are no longer cupped as well, which was a nice perk. I recommend it, personally, as it seems to make a lot of sense...I can also now use the space for storage. It costs a ton of money, however.

[sacredgrooves]

Fully encapsulated crawlspaces are really nice, and I own a company that installs them. With that said, if you want to save a large chunk of money, you can acquire 90% of the benefit by taking these steps; laying 100% vapor barrier on the ground (overlap and seal with moisture resistant tape), seal the vents with Polystyrene foam board, and use an appliance grade dehumidifer with a permanent drain. The commercial level dehumidifiers are quite costly, and in reality do not work much better at removing humidity than a Lowes/Home Depot dehumidifier. They will probably last longer however, but of course you can buy 4-5 Frigidaires for the cost of 1 Sante Fe.
You cannot vent crawlspace air and reduce relative humidity when the air you are taking into the crawlspace from the exterior to replace it with is also 80-90% humidity. Feel free to message me with any questions. I will go into all the detail you ever want to know lol.

This website is a project by a group of building scientists out of N.C. State University that have performed a dozen year study on crawlspace moisture about an hour east of me. There is video presentation that will give you a lot of insight into why venting a crawlspace in the Southeast makes no sense. http://www.crawlspaces.org

[texdav]

If I had a chioce having lived in both it would be a slab that has under reamed foundation. Indivdual piers is pretty much not done anymore because of move,ent problems that can efrfect floor especailly tile. It also in time cause alot of framing problems if you ever worked on a pier house. It has to be leveled and then the probelm corrected. A chainwall with deep footing depending on under soil type is much better. But even then it will be nosier than any slab.Insurance company charge more for any open floor type foundation with wooden subfloor because of fire hazards and this is why a agent will tell you to skirt the house opening.Tis of course can lead to frainage and mositure problems.

[hdwell]

I insist on a slab floor. People talk about the pipes breaking, but ever had frozen water pipes under the house (a pier house)? You can keep the crawlspace, I want a slab!

[RayinAK]

In the interior of Alaska we have both types of construction, on both cheap and expensive homes. I prefer concrete foundations, and deep enough to have a basement I can walk around without bunking my heat on the floor joists or pipes. I don't see a single reason for having a crawl space since this is wasted space. A basement can be used to store things, or even to live in. One can have one or more furnished rooms in there, with a shower or small bathroom, or just a very large storage room.

If the idea is to use a basement for storage, then one can build the house using interlocking foam foundations filled with concrete. The floor can be watertight with 6-mil (or greater) plastic, plus 1" insulating foam panels (blue color) on top of the plastic, topped with a concrete floor. Yes, it would make the project more expensive, but the basement will be water-tight if care is taken during the building process. Best of all, the temperature in there would be cool and stable year round.