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-   -   Concrete infill for cinderblock foundation/crawlspace? (

OzarkCountryGal 06-07-2010 03:45 PM

Concrete infill for cinderblock foundation/crawlspace?
Hello folks! We recently purchased an extreme fixer upper... The majority of the home is in pretty good shape, walls and ceiling, structurally sound. But the floor? Oh the terrible floor. Seems the home sits on a consistently damp spot. It's an older house, built in the last sixties... After all this time the cheap subflooring and the joists(about half of which was replaced around 12 years ago) are just in very poor shape. At this point, I feel it's kill it or cure it. And considering the times, we need to do it cheap. I also want a forever fix. Now I have been doing some rough price figuring, and it seems like all the lumber to completely retrofit a 1400 square foot house would be pretty expensive, even if we used the cheapest available materials. And then there is the matter of it all going to boot in 15 or twenty years due to the moisture issue. Soooo... I came up with an idea, and I want some advice on whether it would work or if I am just a lunatic for thinking it might. :D

Here goes... The house sits on a raised concrete block foundation. The depth, varyingly, from the dirt to the floor is about 2-3ft. I thought If I could fill this box formed by the cinder block with a great deal of rock from the property, and then a layer of medium aggregate gravel from the local rockyard, I could have concrete pumped in to form the typical 4 inch thick slab to be my floor. Is that nuts? I know there would be some structural logistics to consider... All of the joists and whatnot would have to be torn out... All the walls that they support would need to be fortified so the whole joint didn't tumble. I thought I could build concrete block footings(or pour, whichever) for posts that I intend to replace many of the interior load-bearing walls with. Would that be adequate? I really don't understand a lot about what keep a house up and together, I guess that is why I am here. :o I just think it might be possible. The rough figuring I did put concrete at about half of lumber, but even if it came out to the same price I would still rather have the rock solid concrete that will last forever rather than lumber that will need replacing in years to come.

So what do you think? Undoable? Doable? If it IS doable, how? Thanks so much in advance! ~*Chrissy

slownsteady 06-09-2010 01:20 PM

So right now, you have a block foundation with a dirt floor under the house. The wooden floors are not protected in any way from the moisture in the ground; is that right?

A few random thoughts:
Sounds like a ventilation problem.

If you filled the box with concrete, you would still have to rebuild the floors, unless you're planning to have concrete floors throughout the house.

I imagine the block walls could blow out when you fill the interior with that much mass.

OzarkCountryGal 06-09-2010 07:47 PM

I had considered all of those things. Yes, dirt crawlspace and then wood subflooring, no moisture barrier. Ventilation isn't REALLY the issue... I think the issue is that the house is built over a shallow capped well. It's just never going to be dry under there, regardless of how well you ventilate. I was planning on concrete floors... Maybe doing tile over that. But I am a fan of solid floors. There might be a slight chance of the cinderblock blowing out, but it just seems unlikely. They are mortared... Not dry stacked. Also, If the first few feet of mass within the box were large local stones/rocks, I think that by their nature they are going to rest on one another rather than the box of the foundation. Exerting their pressure downward. The gravel and concrete layer will be relatively thin in comparison, so I don't see there being the enormous liquid pressure in an outward direction. I hope that makes sense. :)

slownsteady 06-11-2010 02:03 PM

I'm still thinking the a vapor barrier and some ventilation could solve the underlying problem. Your's is not the only house built this way. Talk to neighbors; one of them (or more) has had the same problem.

I don't know the dimensions of your house, but by the time you find, pay for, and transport all that rock....well maybe you just want to jack up the house and build a new foundation.

itsreallyconc 06-15-2010 04:07 AM

slow 'n' steady makes a good point,,, we did several homes over in warren cty just for that same reason.

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