Questions on pouring concrete around new rough-in

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by Vinniejt76, Aug 28, 2008.

  1. Vinniejt76

    Vinniejt76 New Member

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    10
    I moved my rough-in in my basement about 10 feet. I've already rerun the new pvc and I'm about to pour the new concrete back into the trench I dug. Are there any things I should consider before pouring? I'm going to use cardboard around the toilet drain to create the space needed for the flange to fit. Can the concrete be poured right around the new drains? Do I need to replace the vapor barrier? Should I put gravel back into the holes here the drain isnt? should I replaced the wire that I cut out ( the trench is about 12 in wide)? Is there a specific type of concrete I should use? And finally,should the concrete be poured all at once?
  2. Redwood

    Redwood Master Plumber

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    Have you had it inspected yet?
  3. Vinniejt76

    Vinniejt76 New Member

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    yes, its been inspected.
  4. sjsmithjr

    sjsmithjr Geologist

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    Location:
    Knoxville, Tennessee
    Concrete

    Are you planning on bag mixing or having it delivered? Did you saw cut the existing slab? Where are you located (state would be close enough)?
    Last edited: Aug 28, 2008
  5. Redwood

    Redwood Master Plumber

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    Also you have refilled the hole...
    How have you compacted the earth?
  6. Vinniejt76

    Vinniejt76 New Member

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    I live in Maryland. I was going to mix bags. It's an area of about 12 feet long and 1 feet wide. Honestly, not a lot of dirt came out of the hole. It was about 4-5 inches of concrete and another 5-6 inches of gravel. I used a saw for some, but mostly a jack hammer.
  7. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    You started out with approx. 4 inches of gravel, a vapor barrier to prevent water vapor and radon migration, and wire mesh to make the 3000 psi slab resistant to cracking.

    I would but the soil back in excavation, compact (hand tamper), put the gravel back in, compact, put the vapor barrier back in, and use 5000 psi high early strength bag mix. If the sand is dry, you may need to wet it a bit to get good compaction. You want the grains to stick to each other; you can make a golf ball sized clump by hand to check. Use the 5000 psi bag mix because when you mix concrete in a wheelbarrow, you rarely achieve the rated strength. Try to resist the temptation to get the concrete too wet.

    Unless you can tie the new wire to the old, I don't think your trench is wide enough to require replacement. If the existing concrete is sufficiently rough (like you'd get from using a demo hammer), the new concrete will key in and won't settle. If you have sections that are slick from top to bottom, consider roughing it up. I don't think it will be necessary to use rebar dowels, but I haven't seen it and I don't know how well the underlying fill will be compacted.

    Someone is bound to come along and say this is overkill, but this is how I would do it.
    Last edited: Aug 28, 2008
  8. Redwood

    Redwood Master Plumber

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    7,450
    Location:
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  9. Vinniejt76

    Vinniejt76 New Member

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    Thanks guys, edge is pretty jagged, so the new concrete should "key" into the old pretty well. I don't think I need new mesh because the tench is only 11 inches wide. I'll put the dirt and gravel back in and compact it. Is there a certain type of tape that I should use to replace the new plastic to old?
  10. sjsmithjr

    sjsmithjr Geologist

    Messages:
    295
    Location:
    Knoxville, Tennessee
    At the local hardware look around the weatherstriping supplies for something like Frost King Polyethylene Tape.
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