Crawl Space With Concrete Floor

[richardtb]

I just saw a house that had a crawl space, but instead of the floor being dirt, they had put concrete - with 8 drains.

I had read all the posts regarding slab vs. crawl space, but I have not read anything about crawl space with dirt floor vs. crawl space with concrete floor.

Any comments/opinions would be appreciated.

Richard

[TheNiche]

I just saw a house that had a crawl space, but instead of the floor being dirt, they had put concrete - with 8 drains.

I had read all the posts regarding slab vs. crawl space, but I have not read anything about crawl space with dirt floor vs. crawl space with concrete floor.

Any comments/opinions would be appreciated.

Richard

If you have a photo, we can be more clear as to your description.

It sounds like a house such as is frequently built in Bellaire's flood plain, which is on pier and beam and elevated so that the living area is just out of the flood plain. They almost always use tall concrete headers with brick or stucco siding installed over them so that it looks from the exterior as though the house is on a slab, even if it isn't.

[richardtb]

Thanks.

Here is the listings with pictures...

http://search.har.com/engine/dispSearch.cf...mp;backButton=Y

However, to show you the crawl space, I would have to go & take pictures of it.

The house is in the 500 year flood plain, so it would seem a bit excessive to go through this trouble in case of a flood...

If you have a photo, we can be more clear as to your description.

It sounds like a house such as is frequently built in Bellaire's flood plain, which is on pier and beam and elevated so that the living area is just out of the flood plain. They almost always use tall concrete headers with brick or stucco siding installed over them so that it looks from the exterior as though the house is on a slab, even if it isn't.

[TheNiche]

Thanks.

Here is the listings with pictures...

http://search.har.com/engine/dispSearch.cf...mp;backButton=Y

However, to show you the crawl space, I would have to go & take pictures of it.

The house is in the 500 year flood plain, so it would seem a bit excessive to go through this trouble in case of a flood...

Yep, its like what I'd told you about. Pier and beam with tall headers. Bellaire and West U both require living areas to be built above the 500-year flood plain. When you were talking about drains, I'd originally thought that you were talking about vents in the headers, but now I've got a sense of what you're dealing with, where the drains feed water into the public sewers.

Its possible, I suppose, that something about the site and building codes made it difficult to route water away from the house and toward the street, so instead they just decided to route the water under the house, with the impermiable concrete floor and numerous drains as an attempt at keeping the soils around the piers from expanding and contracting each time that it rained, which could otherwise cause foundation trouble in a few years. I'd suggest that you look very closely at the site and watch closely how the ground slopes, and where water would likely go during a rain.

[richardtb]

Thank you so much!!!

Yep, its like what I'd told you about. Pier and beam with tall headers. Bellaire and West U both require living areas to be built above the 500-year flood plain. When you were talking about drains, I'd originally thought that you were talking about vents in the headers, but now I've got a sense of what you're dealing with, where the drains feed water into the public sewers.

Its possible, I suppose, that something about the site and building codes made it difficult to route water away from the house and toward the street, so instead they just decided to route the water under the house, with the impermiable concrete floor and numerous drains as an attempt at keeping the soils around the piers from expanding and contracting each time that it rained, which could otherwise cause foundation trouble in a few years. I'd suggest that you look very closely at the site and watch closely how the ground slopes, and where water would likely go during a rain.

[RedScare]

Are you talking about a pier on slab, similar to what you describe in a previous post?

http://www.houstonarchitecture.info/haif/i...mp;#entry196196

A house around the corner from me used this system. It consisted of a slab on grade, with a wood foundation built on top of it, creating a crawlspace. The floor ended up being about 3 feet above the slab. If you had asked this question about 3 months ago I could have taken a photo, but it is now covered with siding. I am not sure of the advantages of this system over a standard pier and beam, unless perhaps the slab is cheaper to build.

That house is the only one I have seen built in this manner. All of the others around me are built with pier and beam.

[richardtb]

No, it is pier and beam. The answer that TheNiche give makes a lot of sense: There must be some drainage problem and so by having concrete and 8 drains, it drains better than if the water had to go through the soil.

The other reason why the answer ty TheNiche makes a lot of sense is that when we went to the open house all the windows were open, even though it was not all that warm that day. So, it makes sense that there are some humidity problem with the house and that is why they had all windows open for the open house (to get rid of mildew smell).

Are you talking about a pier on slab, similar to what you describe in a previous post?

http://www.houstonarchitecture.info/haif/i...mp;#entry196196

A house around the corner from me used this system. It consisted of a slab on grade, with a wood foundation built on top of it, creating a crawlspace. The floor ended up being about 3 feet above the slab. If you had asked this question about 3 months ago I could have taken a photo, but it is now covered with siding. I am not sure of the advantages of this system over a standard pier and beam, unless perhaps the slab is cheaper to build.

That house is the only one I have seen built in this manner. All of the others around me are built with pier and beam.

[musicman]

water shouldn't be going under a house period. if water was regularly going under a house, i sure would be concerned.

many times the owners are too cheap to pay the power bill so the air conditioning isn't on during showings. if you smell mildew...that's not a good thing.

Edited February 11, 2008 by musicman

[TheNiche]

No, it is pier and beam. The answer that TheNiche give makes a lot of sense: There must be some drainage problem and so by having concrete and 8 drains, it drains better than if the water had to go through the soil.

The other reason why the answer ty TheNiche makes a lot of sense is that when we went to the open house all the windows were open, even though it was not all that warm that day. So, it makes sense that there are some humidity problem with the house and that is why they had all windows open for the open house (to get rid of mildew smell).

Just to be clear, I'm engaging in reasoned speculation. If you're really interested in this house, figure out what happens in a storm. I could be wrong; stranger things have happened.

When you mentioned open windows during showing, my first thought was that it was a new house and that some freshly installed construction materials release unpleasant fumes at first, and that they might've just been airing it out...but HAR says 2006 was the year built, so if that is accurate, I'd say that you've got yourself a couple of red flags to investigate. Add one more red flag if the home had been bought new and then occupied for only a year or so.

[richardtb]

I looked at another house and it said "foundation is structural slab on pier and beam." Again, how does that compare to just pier and beam? In other words, how does it do if the ground moves, how is it with respect to humidity & termites.

I just saw a house that had a crawl space, but instead of the floor being dirt, they had put concrete - with 8 drains.

I had read all the posts regarding slab vs. crawl space, but I have not read anything about crawl space with dirt floor vs. crawl space with concrete floor.

Any comments/opinions would be appreciated.

Richard

[RedScare]

I looked at another house and it said "foundation is structural slab on pier and beam." Again, how does that compare to just pier and beam? In other words, how does it do if the ground moves, how is it with respect to humidity & termites.

A structural slab on pier and beam is a concrete slab supported by piers and beams. A "pier and beam" has the same piers, but usually has wooden beams on top of it. Sometimes, they are steel support beams. A structural slab on pier and beam may look similar to a slab on grade, except that the slab is not supported by the dirt underneath, but rather by the piers and beams. Think of a parking garage, where the piers, or columns support horizontal beams. The slab is poured on top of the beams.

As for movement when the ground moves, a structural slab on pier and beam, because it is not in contact with the ground, will not move, as long as the piers were properly built.

Edited February 11, 2008 by RedScare

[Mark F. Barnes]

Red is dead nuts on, and those piers need to be bell bottomed for the absolute best results. In this area, it's not a case of "If the ground moves" it's "When and how much. Black gumbo is the absolute worst when it comes to swelling with moisture entering and leaving the soil. I installed a moisture system in conjunction with mine to keep my ground more consistent. Black Gumbo can move a slab house nearly a foot in certain conditions, especially if the builder did not engineer for it. Piers can be added afterward for a big expense, however highly effective if done correctly. keeping the ground moist can help also. It's the differentiation between wet and dry that's the killer.

[richardtb]

Do I understand correctly then that "structural slab on pier and beam" means the same thing as "slab on builders piers"?

A structural slab on pier and beam is a concrete slab supported by piers and beams. A "pier and beam" has the same piers, but usually has wooden beams on top of it. Sometimes, they are steel support beams. A structural slab on pier and beam may look similar to a slab on grade, except that the slab is not supported by the dirt underneath, but rather by the piers and beams. Think of a parking garage, where the piers, or columns support horizontal beams. The slab is poured on top of the beams.

As for movement when the ground moves, a structural slab on pier and beam, because it is not in contact with the ground, will not move, as long as the piers were properly built.