Hello Folks,

Just wanted to get a sanity check from those that have experience in this area.

If I am proposing to add a 21' slab addition to an existing slab that has a 12"x12" beam and piers, what should be the number of doweled holes and the depth?

Thank you very much, tom

This message has been edited. Last edited by: tstex,

Not real sure what you are trying to do. Is there any thing significant in the 12" X12" piers that you refer to. To adding a slab to the existing slab that's done on the edge. ??. Maybe a better definition or pic would help. Sorry Tom.

SOrry, I will re-define

We have an existing slab that has 2500sqft on the 1st flr, and 2nd story another 2000sqft of living space.

The entire perimeter of the foundation has a beam in it of at least 1ft with piers around both the perimeter and w/in interior. There is a straight 21 feet of the current foundation that we want to add a new foundation to and extend outward. So, before the new foundation is poured to adjoin the current one, I wanted to know what are the proper specs of how to connect the two foundations via drilling into the current one and putting rebar in the current one, then tying the doweled rebar [of old slab] to the rebar that will be used in the new foundation.

My questions pertain to people that have experience with joining concrete slabs regarding:

number and placement of drilled holes in the old foundation

how deep to drill

thickness of rebar going into the drilled holes

how to secure the rebar placed in the drlled holes [type of material to spec]

distance between drilled holes from left to right

single doweled holes, one of top of each other

Hope this is better clarification.

Thank you,
tstex

This message has been edited. Last edited by: tstex,

I have done a good bit of concrete work and could give you what I think you would need but sounds as if you want an engineers point of view. Sorry.

Hopefully you have a set of plans to show you this info. Building practices differ from area to area. Check with your local building department.

#4 rebar, epoxy glued into the old slab 12 inches deep, 2 ft on center. Footing of foundation use 1 upper and 1 lower rebar 12 inches deep, running out as far as you can.

This message has been edited. Last edited by: Re-mdlr,