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  1. #1
    Join Date
    Jul 2008
    Posts
    33

    Default dirt floor basement

    Hi. I have a house from 1830 and it still has the dirt floor basement! I want to concrete it over and use the space for storage and stuff. The ceiling is only 5' high, so I was wondering what is the minimum thickness the slab would have to be. Could there be a code where I live, or is there an industry standard for minimum acceptable slab thickness? An architect told me that a standard "rat" slab is usually 2-3 inches. I guess with aggregate and fiber mesh, it should be enough to hold. It's not a garage floor where cars will drive on it.
    Thanks.

  2. #2
    Join Date
    Aug 2008
    Posts
    66

    Default Re: dirt floor basement

    The most important thing to consider is what the basement WALLS are made of.
    You didn't mention what the walls are made of (loose stone, cemented stone, cement block, masonry block, poured concrete, brick, etc.,etc.)---anytime you go down lower on the basement floor, you have to go down lower & REINFORCE the basement walls in that area----that's not to say that you have to excavate the entire basement---many homeowners usually need only a PARTIAL cellar that has a finished height of approx 7 feet to allow for local codes, tall persons, & duct work, wiring, lights, etc.

    This type of work is almost always left to a contractor due to the specialized equipment and work needed, and often the code approval of the local town you live in; anytime you modify the basement walls,you involve STRUCTURAL issues that can affect the safety of the house occupants; the town wants the contractor to have a civil engineer draw up a construction PLAN detailing how many feet you have to excavate in front of the existing wall & how you intend to brace the existing walls with the new BENCH FOOTING WALLS, UNDERPINNING WALLS, or full height concrete or concrete block walls.

    Thus, to get a finished partial or full basement with a 7' height, 4" of crushed stone, 4" of concrete & perhaps a drain or two. (12" to 14" floor) would equal 8', minus the 5' existing, means you would have to excavate 3' along the basement walls to be modified, and reinforce the existing wall in this area with at least 4' of poured concrete (or mortared blocks if allowed); some towns require that the poured concrete for the new wall equal the height of the existing wall, thus creating a DOUBLE WALL for structural safety---thus, a partial 7' basement becomes more attractive in money savings if you have a town building dept. that follows strict guidelines on structural safety---it's another good reason to have at least one or two contractors come over the house to survey the situation & advise you beforehand of what to expect from the town you live in; consult the Yellow Pages under "Basement Contractors", or under "Contractors"

    For info on the internet, Google excavating cellar walls, BENCH FOOTING; UNDERPINNING.
    Also Google bench footing basement walls
    Also Google Cochren Foundation basement lowering
    Last edited by dodsworth; 04-25-2012 at 03:36 PM.

  3. #3
    Join Date
    Jul 2008
    Posts
    33

    Default Re: dirt floor basement

    Quote Originally Posted by dodsworth View Post
    The most important thing to consider is what the basement WALLS are made of.
    You didn't mention what the walls are made of (loose stone, cemented stone, cement block, masonry block, poured concrete, brick, etc.,etc.)---anytime you go down lower on the basement floor, you have to go down lower & REINFORCE the basement walls in that area----that's not to say that you have to excavate the entire basement---many homeowners usually need only a PARTIAL cellar that has a finished height of approx 7 feet to allow for tall persons, & duct work, wiring, lights, etc.

    This type of work is almost always left to a contractor due to the specialized equipment and work needed, and often the code approval of the local town you live in; anytime you modify the basement walls,you involve STRUCTURAL issues that can affect the safety of the house occupants; the town wants the contractor to have a civil engineer draw up a construction PLAN detailing how many feet you have to excavate in front of the existing wall & how you intend to brace the existing walls with the new FOOT WALLS or full concrete or concrete block walls.

    Thus, to get a finished partial or full basement with a 7' height, 4" of crushed stone, 4" of concrete & perhaps a drain or two. (12" to 14" floor) would equal 8', minus the 5' existing, means you would have to excavate 3' along the basement walls to be modified, and reinforce the existing wall in this area with at least 4' of poured concrete (or mortared blocks if allowed); some towns require that the poured concrete for the new wall equal the height of the existing wall, thus creating a DOUBLE WALL for structural safety---thus, a partial 7' basement becomes more attractive in money savings if you have a town building dept. that follows strict guidelines on structural safety---it's another good reason to have at least one or two contractors come over the house to survey the situation & advise you before hand of what to expect from the town you live in; consult the Yellow Pages under "Basement Contractors", or under "Contractors"

    For info on the internet, Google excavating cellar walls, BENCH FOOTING; UNDERPINNING.
    er.............um................thanks, but no thanks.
    I have NO intention of digging ANYTHING out.
    I just wanna pour concrete on whats there and use what I got.
    Everybody wants to give me more work to do.
    Have you been plotting with the wife against me?

  4. #4
    Join Date
    May 2008
    Location
    Pacific Northwet
    Posts
    1,361

    Default Re: dirt floor basement

    First of all, building permits are only good for three things: making building inspectors (and possibly your insurance company) happy, making future buyers of your house happy, and recording improvements so your taxes can be increased. Getting a building permit doesn't do YOU any good.

    Codes are there to ensure basic safety. They do not ensure the quality of construction.

    People think the building inspector will make sure it's built right. The inspector only makes sure it's to code, and there have been quite a few that don't take their job seriously. Besides, you can't hold the inspector accountable for missing a critical detail.

    Sure, you can pour a concrete floor, you just won't be able to market it as living space. As long as you're not doing any structural changes, and you are providing a vapor barrier or an escape path for moisture, I can't see how putting a floor in there will impact health, safety, or durability of your home.

    One more thing codes and permits are good for: protectionism for the building trades industry.

    * * * * *

    I wouldn't do less than three inches, on undisturbed or compacted soil/substrate. Two inches seems to be kind of weak, even when not under a heavy load. Remember that concrete will ALWAYS crack as it cures; you need to ensure that once cracked it doesn't shift.
    Last edited by Fencepost; 04-27-2012 at 01:48 AM.
    The "Senior Member" designation under my name doesn't mean I know a lot, it just means I talk a lot.I've been a DIYer since I was 12 (thanks, Dad!). I have read several books on various home improvement topics. I do not have any current code books I can refer to. I was an apprentice plumber for two years.

  5. #5
    Join Date
    Jul 2008
    Posts
    33

    Default Re: dirt floor basement

    Right.
    Permit, Shmermit.
    Inspectors don't really do all that much. I know a few!
    I just could use some storage space for tools, holiday decorations.........and assorted junk. Er......um....I mean stuff. I just wanted to know what the minimum was as far as slab contruction. I guess a higher compressive strength may work?
    Fiber mesh is cheap, but effective. I already have heavy plastic down there, but, I want to make it a bit nicer. Thats all. It'a a good 40x25 feet down there........so why waste it?
    Thanks.

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