Added a slab to existing concrete

[Usafexplorer]

We have a footing that was recently poured for an animal building so we left areas dirt for pens. My wife now wants an area enclosed within the building as a clean room for animal care and storage. Any suggestions on what needs to be done to add a slab within the grid area on the attached pic?

In my DIY mind it requires an expansion joint on 3 sides and rebar tied in to the existing footing to keep everything together, kinda wish we did this when it was poured but too late for that.

 

[The Cobbler]

I'm having a hard time understanding the concept here. what are the dirt areas and how deep are those walls .
so far I'm agreeing with you on the expansion on 3 sides but not rebar tied to the footing

 

[Usafexplorer]

I'm having a hard time understanding the concept here. what are the dirt areas and how deep are those walls .
so far I'm agreeing with you on the expansion on 3 sides but not rebar tied to the footing

They are really just a footing, 24" deep. The dirt areas on the lean-to sides are for animal enclosures.

 

[The Cobbler]

I guess my question is why not pour it all concrete , but that wasn't your question so I digress.
but I would not tie the pad to the footing walls . keep them separate

 

[Usafexplorer]

I guess my question is why not pour it all concrete , but that wasn't your question so I digress.
but I would not tie the pad to the footing walls . keep them separate

Because we didn't want concrete throughout the entire structure. Maintaining livestock on concrete is more headache than we wanted. A gravel/dirt base is much easier and cleaner for maintenance.

Why not tie in with rebar? Just trying to understand the methods and logic, appreciate the input.

 

[The Cobbler]

in my opinion you don't want the pad tied to the walls so if there's frost heave it can float & settle back . if it's pinned to the walls it can't float and will cause stress cracks from heaving .

 

[Rusted Nut]

Make sure your dirt base has good compaction and good support for the slab. Expansion joints are good, no need to tie rebar into the footings. You could put rebar or mesh in the slab if you want.

 

[Usafexplorer]

in my opinion you don't want the pad tied to the walls so if there's frost heave it can float & settle back . if it's pinned to the walls it can't float and will cause stress cracks from heaving .

Gotcha, thanks

 

[Usafexplorer]

Make sure your dirt base has good compaction and good support for the slab. Expansion joints are good, no need to tie rebar into the footings. You could put rebar or mesh in the slab if you want.

Will do, thanks for the input

 

[wssix99]

You don't need to do a thing other than compact the fill underneath the slab. Joints are not needed because the slab will shrink as it cures and pull away from your footings. (If you put an expansion joint there, you will just have an expansion joint with a gap after the cure.) So, I would just do nothing regarding joints and then use a crack filler between the slab and footers after the 30 day cure.

No need to tie the slab into anything. If the ground is underneath flat, (not on a hill) its not going to go anywhere.

Depending on the size of the slab, you may need saw cut contraction joints.

 

[PopcornSutton]

I agree with cobbler. The slab over the footings will act differently than slab on grade. And most definitely cut control joints where the footing is and take them across the slab to the other side. Both sides and end of the footing area. The long joint won't be centered but the slab will crack without the joint there.

 

[jblnut]

Maintaining livestock on concrete is more headache than we wanted. A gravel/dirt base is much easier and cleaner for maintenance.

I’d argue that point for as long as you’d listen.

Short term yes, it’s easier as any liquids will soak into the dirt. Long term that’ll cause issues as all those liquids build up and start growing nasty bugs that’ll affect the health of your animals. It’s not as big of an issue outside where rainwater helps clean things up. Dirt has advantages for traction issue with hooves but that’s about it. Wooden walls will also trap nasties and eventually cause issues if they’re in animal contact areas.

Concrete can be cleaned down to its surface and washed if needed. Seal it and very little will live in it. You won’t ever struggle with cleaning the pens if a waterer flows over and makes a muddy mess. Clean the bedding off and rebed. Move on no big deal. Cleaning the bedding off will be a lot easier as well.

Only advantages to dirt floors are less expensive up front and some mild traction advantages. The traction advantage is very easily solved with some coarse barn line or grit.

I agree with what was said above to just pour it inside the footers. It’ll shrink and you’ll have your gaps you need. If there will be animals up against it’s not a horrid idea to seal the gaps so “stuff” doesn’t go down in there. I used roofing tar in my steer barns and some unremembered goo in the chicken barn.

 

[Lumpy102]

in my opinion you don't want the pad tied to the walls so if there's frost heave it can float & settle back . if it's pinned to the walls it can't float and will cause stress cracks from heaving .

I'm thinking they don't get much frost heaving in "coastal North Carolina" but I don't live there, so I may be wrong

 

[racecougar]

I'm thinking they don't get much frost heaving in "coastal North Carolina" but I don't live there, so I may be wrong

Expansive soils are a concern in NC, depending upon where the OP is. Either way, I wouldn't tie the slab to the foundation.

 

[CraigStu]

The 2 garage additions I have done both had footers and then several courses of block to create stem walls. The slab was near the last step in construction. The slab had rebar in it but no rebar attached to the walls. Both contractors said the walls will be generally no movement since the footers are below frost depth. But the slab may move slightly and it is better to just let it move than try to restrict it.

 

[mreisner]

I would let it flow and sings it's inside on the front edge I wouldn't or not really a footer but just a rat wall as your other walls will act as a rat wall. Feed and stuff will be kept around their rodents can be a concern.

 

[Usafexplorer]

Appreciate the replies and scope of experience on this question, I feel better equipped to handle the slab pour and again thank everyone for their input.

 

[ConCretin]

Presumably there is a structure is going over the foundation? Is there a CMU or concrete curb wall or will the structure bear directly on the foundation?

If you don't want to get into more detail, I'll just offer a response to your questions. There is no need for expansion material but if you use the type with a removable top strip, it provides a great way to seal the perimeter with a caulk joint. You may want to reinforce the slab itself with wire or rebar but don't pin it anywhere so the slab can move independently from the foundation. It doesn't look big enough to require control joints.