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Old 11-16-2009, 10:59 AM   #1
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How to cover a hole in a floor slab

The "genius" I bought my house from remodeled his outdoor carport and poured a concrete floor over it, to turn the carport into an interior room, and in the process he poured that slab right over the access to his septic tank!

So now I have to bash a hole in the slab to pump out the tank, and I want to replace the hole I'll make with something that is removable the next time I or a new buyer has to pump out the tank again!

I need to create a 32" square opening in the concrete slab that forms the floor of my interior home office. I'm considering a range of options for making a removable hatch that I could set down into the opening on a frame of some sort that would be anchored to the insides of the opening.

I figured out the slab I'd cut (assuming I can cut out the existing floor at all, which is a different subject) would weigh so much that reusing that would be impractical. No one could easily lift it out of the opening.

I'm considering a steel or aluminum plate about 1/4" thick, supported on some sort of metal frame anchored to the insides of the opening. Would a steel or aluminum plate 1/4" thick, and 32" square have the necessary load bearing capacity to become part of a normal room floor? I assume yes, but I'm not a structural engineer. How heavy would a piece of "vanilla" carbon steel plate 1/4" thick and 32" square weigh, anyway?

I'm also considering just using 2x4s for the frame around the insides of the opening, and putting a piece of 3/4" plywood on it, to form the removable hatch. Perhaps I'd put some 2x4s under the plywood to give it some stability in the center of the 32" span in each direction. Would THIS have the necessary load bearing capacity?

What else can anyone suggest? Or can anyone think of problems with whatever I'm considering?


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Old 11-16-2009, 11:56 AM   #2
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you can buy a round cover and extension ring that is made for this. It will extend the opening and provide a finished cover. Or leave out the cover and make one with the finished floor material. You can then pour cement around the concrete extension ring to finish off the flooring.


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Old 11-16-2009, 12:14 PM   #3
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Thats not a good situation, but I don't need to tell you that I guess.
Is it possible part of the tank is outside? Could you create a new access hole outside the building?
Wow, thats a screwy deal. I also wonder if you need to fabricate some type of gasket system for the tank cover so you do not end up with sewer gas in the house if you do keep the cover location were it is.
"It looked good on paper, but paper is funny that way"

Time to Get Up Out of Your Chair and Do it Yourself!
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