Modern Driveway Slabs

17 days ago

Hi there! Is it normal for a modern driveway/geometric design - with concrete slabs poured in place - to have concrete spillage between the slabs? I was under the impression it would be a series of individual concrete slabs and we would be able to see the ground in between (and then would fill with stones), but our contractor is saving he can’t break that concrete up in between because it would effect the structural integrity of the slabs. Water is now pooling in between the slabs, so he said he would drill holes there. I can’t tell if I’m being taken for a ride or not! Any help would be appreciated.

Featured Answer

3onthetree

15 days ago

It is 100% common when pouring concrete flatwork that you have underflow below the formwork. Typically a 2x4 is used to get around a 3 1/2"-5" thick slab, so you can see there is going to be a small gap and maybe more depending on the base sloping. It is not a big deal, and typically you would just grade your soil up against the slab to cover the underflow. If you cared, you could chisel off some of the edge, it shouldn't affect anything about the slab.

With your design of a grid of slabs, this underflow touching the adjacent slab's underflow will provide no structural capacity to keep them aligned. Only embedded steel (rebar or Welded Wire Mesh) could limit separate slabs from moving horizontally or vertically in relationship to each other.

It is possible a slab is designed to have "insets" where bricks/pavers are inlaid. In that case, the thickness below the "inset" would need to be min 3 1/2" thick. Drainage in the recesses would be a good detail to consider. I don't think this would be a chosen design for grass.

Without pics, it sounds like you can chisel out the underflow. The base under the concrete is going to determine how much each slab moves.

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Comments (14)

millworkman
16 days ago
" I was under the impression it would be a series of individual concrete slabs and we would be able to see the ground in between "

What did the contract and drawings show? First mistake was assuming. Of course you can have individual slabs under most circumstances. Post up pictures of what you have and an idea of what your impression was you were getting for better advice.
arcy_gw
16 days ago
WHY do you want gaps in your slaps? Were you thinking of planting some sort of ground cover to put a green design to your driveway? If not then the gaps would quickly fill with weeds...we need pictures to totally understand your dilemma
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PRO
Patricia Colwell Consulting
16 days ago
last modified: 16 days ago
Slabs poured ??? You either have a slab driveway or a poured concrete driveway . I need pics posted her ein a comment DO NOT start another post . Why did you want gaps filled with stones that will constantly be picked up by tires .BTW where do you live?
millworkman
16 days ago
Would I be correct in assuming this is the look you were going for, except using stones instead of the grass?
PL
Original Author
16 days ago
That’s exactly right!
PRO
BeverlyFLADeziner
16 days ago
They can pour individual concrete squares in Florida because it never gets cold enough for heave and thaw. If you are in a climate that freezes, then having the squares linked probably makes more sense. However, you don't want water collecting in the 'gutters' between the slabs because if the water freezes it will break up the concrete.

https://designnsuch.wordpress.com/2011/10/15/backyard-concrete-paver-update/
PL
Original Author
16 days ago
Never had a driveway previously so admittedly went in blind - beyond Pinterest pictures of designs we liked. We trusted the referral we had, who seemed to be a known quantity. The contract said it was “individual concrete pads.” The pads had spillage beneath the forms - you’re going to need to forgive me if I’m not using the right language - and all the pads are connected by crumbly concrete. We were told that holes could be drilled in that interconnected concrete for drainage purposes but otherwise it needed to stay to stop the pads from “floating.” Definitely did make some assumptions, but you live and you learn! I’m not planning to make any other posts on this forum; the person instructing me not to make another post can calm down!
Pugga70
16 days ago
Following....
PL
Original Author
16 days ago
We’re not in a climate that freezes (except once in a blue moon). Do connected pads with some drainage in between (drilled holes) make sense in this climate?
PRO
Joseph Corlett, LLC
15 days ago
Tell him to get his concrete saw out and make the driveway you want please.
PL
Original Author
15 days ago
Thanks, this is very helpful!
PRO
Debbi Washburn
15 days ago
Can you post pictures of what you have? Did they give you any pictures indicating what the final product would look like?

I have no solution to offer, but there are some smart folks here - they just need pictures.
K Laurence
12 days ago
I have exactly what millworkman posted except the poured in place pavers ( that’s what they’re called ) are filled with smooth beach rocks. I’ve had them for several years & no, tires do not pick up the rocks, lol 😂.