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Community and Q&A

Rebar & Tapcons?

scoutingeuropa | Posted in General Questions on

My house is 60 years old. I have trenched the perimeter of the basement floor ( 25′ x 35′). The drain tile ditch is 23″ deep and 18″ to 24″ wide. All saw cut. I have also saw cut down the center for new main sewer line and 45 degree over (wye) for drains for HVAC equipment . Along walls and corners are other new drains, wash machine drain and bath room rough in. I have two large open areas, one is about 4′ x 12′ and another is 6′ x 8′. The existing concrete varies in thickness. A good average is about 2 1/2″ thick. A lot of it being 2″. The new concrete will be 3″ or 4′ thick. I want to use 3/8 rebar in the two large open areas and a heavy flat 6 x 6 wire in the trenches. My thought was to doll 3/8 rebar in the foundation wall for the entire perimeter, 3″ to 4″ into existing concrete wall with a 6″ stick-out. Dowels for the existing floor concrete are 1/4″ tapcons. All rebar areas on 24″ centers, 18″ centers for wire mesh. For interior ditches: I can use a 2 1/4″ Tapcon not fully screwed into existing floor concrete, 1 1/4″ into existing floor concrete with a one inch stick-out. Tie wire mesh to one inch stick-out on one side of ditch and wire tie to opposite side also with a one inch Tapcon stick -out. In the large open areas: using all 3/8″ rebarb, my thought was to use one 1 1/2″ Tapcon through a piece of 1/4 x 1/4 x 1 1/2″ aluminum angle 1 1/2″ long ( I have plenty) screwed to existing concrete floor. Set the 3/8 rebar on the 1 1/2″ long aluminum angle and wire tie it off. The other end of the rebar tied to the 6″ 3/8 rebar stick-out from foundation wall. Open areas with 3/8 rebar I will install 3/8 rebar in opposite direction and tie for 24′ squares. For perimeter ditches: Tie 6 x 6 wire mesh to the 2 1/4″ Tapcons with a one stick out from existing floor concrete. Tie opposite side of 6 x 6 wire mesh to 3/8 rebar with 6″ stick-out from foundation wall.
Whatta ya think? I want to minimize cracks by using the mesh and rebar. Another concern is that the Tapcons and/or aluminum angle will only have only an inch of new concrete cover because of the 2′ to 2 1/2′ 60 year old concrete floor.

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  1. Expert Member
    Malcolm Taylor | | #1

    By all means rebar, tap-con and wire mesh any and all the slabs you want together, but don't attach them to the existing foundation walls. They need to be able to move independently. You should leave an expansion-joint around the perimeter. The slab will move both initially and seasonally. it will also probably sink a bit. If you tie it to the foundation it has nowhere to go.

  2. scoutingeuropa | | #2

    Thanks Malcolm. Will do. By not tying the slab to the foundation, does that create the expansion joint you are talking about?

  3. Expert Member
    Malcolm Taylor | | #3

    The best practice is to include a joint filler, but that said, just leaving the two unattached is the most common way of doing it.

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