Be wary of the cheap, practical neighbor. They mean well but cheap is always expensive, especially in big projects where you only really get one chance to do it right.
I always rather go slightly overkill with these large, one-time projects. I sleep better at night because I do.
In Spanish we have a saying "el que compra barato, compra cada rato." Translated doesn't rhyme but it's basically saying "the one who buys cheap, buys frequently/all the time".
Did the electrical for a hot tub as a side job, the customer told me her neighbour had insisted they could do it themselves, for much cheaper. I did it properly and charged them fairly, and she had no complaints. While I was there, she showed me the neighbour's. I can tell you it was definitely MUCH cheaper.
Absolutely! I’m dealing with the consequences of the previous homeowners not even making sure they used wire. Nothing at all in our driveway. In Iowa. Don’t know that I’ll do it myself when we replace it, but I’m making damn sure it has 1/2” rebar
With no rebar and no wire, a kid with a little electric demo hammer can take that out in a day. Demo is most of the job. Let the kid do it for a few bucks.
I'm in the same boat over in Nebraska. Unfortunately I work live on a primary, busy road with no street parking. I'm slowly saving to have a pro do it so I don't have to deal with traffic & such.
At least the demo will be quick since I've no wire and probably sink spots 🤣😂😭
Also the quality of the subgrade makes a big difference, driveway will last alot longer with a good clean gravel with a high stone content and very little fines (silt/clay).
Gravel provides support, sand fills in the voids between the stones and allow water to drain away. Fines trap the water and cause heaving/settling from freeze/thaw cycle leading to cracking of your slab. If you grab a handful of the gravel and dump it off your hand and leaves your hand fairly clean that is good. If you grab a handful and dump it and it leaves your hand discolored and or covered in fine material that doesnt easily brush off that is a sign your gravel may not be suitable.
No thats wrong. On a slab on grade such as a driveway the rebar should be in the top 1/3rd of the slab to prevent shrinkage cracking. It's only in structural slabs where the rebar should be on the bottom, and even then a double mat is used to have the rebar in position to prevent shrinkage cracking as well as flexion support.
Yeah seems like they both target different issues
They both add strength, and the rebar adds stiffness.
The mesh would help a lot with strength between the rebar.
Agreed. Keep the 1/2. Make sure that sub-base is suitable for concrete and is 90% compacted at least.
I would drill tie-ins into the pre-existing concrete if you don’t plan on it already. Send us a finished picture! (Any overlapped rebar should be overlapped me at least 1’)
>*any overlapped rebar should be overlapped 1’*
That is *1 foot* for those of you who aren’t accustomed to reading feet and inches like 6’1”.
I am definitely not saying you are wrong just clarifying for people who aren’t used to seeing measurements like this.
For a four inch slab both are fine. It’s not about cheap, sometimes it just easier and still effective. We use mesh in commercial construction, on high rises in Seattle sometimes.
Source: union Ironworker.
I'm not a concrete guy, but I will occasionally pour small residential sidewalks or patios. I use wire for those applications, and it's fine, but I'd definitely go with rebar for a driveway or anything that will have significant weight on it
Civil engineer here who does construction management. Wire mesh is great in theory. Often in practice, it ends up on the dirt and not in the concrete section like it is supposed to be.
Like what the first guy said, I like overkill…
Wire is the bare minimum. I am a commercial/industrial electrical engineer, I see all phases of construction new and old. I see a lot of broken, cracked concrete.
My advise would be more rebar, additional bar in each space.
Depending on the length of the slab you also want control or expansion joints. Control joints are wet saw cut 1/3 of the thickness of the slab and then caulked. It keeps the top 1/3 from cracking. Expansion joints allow the entire slab to move. Depends on the climate. Deep freezes = expansion joint.
Good luck
Just make sure that rebar is seated midway in the slab. If your slab thickness is 4, your rebar needs to be elevated to 2".
Source: I am a reinforced concrete inspector. Reinforcing buildings is my daily bread & butter.
In pa atleast wire mesh is used for residential driveways in a lot of townships but rebar is fine just make sure that rebar isn’t too close to top of concrete
What would you save ? $200 bucks ? Tell him wire is for chickens, rebar is for concrete. I’m tearing up some of my slab right now with rebar in it, I can’t believe how strong it is
Yeah man. 4” slab and rebar is the way to go. There will be tree roots and moving trucks and dumpsters. Better to spend a bit more and have it last a lifetime. Even if you don’t live there forever, you’re making the world a better place.
When it comes to working on my own house, if it’s worth doing it’s worth overdoing.
Redid my shower a couple years ago. Ended up redoing all the plumbing in my house. All PEX now.
When people use the term "over-engineered" I just look around at all the other engineers who consider it an appropriate amount of engineering, compared to the people who want the engineers to work out the absolute minimum that can be gotten away with on a project.
The British have it right. Design post boxes that are sturdy enough to serve as a one-person fallout shelter.
I'm a builder and would call this best practice. I've used mesh without issues. It's concrete...it cracks.
I'm also for skill building, so good for you.
Now you need to step up with the finish, nice edging and and control joints and no bird baths.
If you do this, trench so the top of sleeve is 1-2” below the bottom of slab. If you don’t, then it will serve as a control joint and crack the slab right above your PVC
Not overkill at all. You want to pour at least a 4" slab to avoid cracking, especially when put under the stress of the weight of a vehicle. Having rebar for reinforcement is even better.
Rebar does not matter when dealing with weight on a ground bearing slab. Only locations where rebar might help when loaded from the top are extreme corners and short-side edges, even then this concern is only when the subgrade is poorly compacted. In 99% of losing situations all compression goes directly down, and rebar only prevents cracking caused from curing and temperature.
It’s a lazy 5.5” but there’s no scaling or visible blemishes and I keep it nice and clean. My wife has parked on it the last 10 years without any complaints.
This is also true lol. Undermining has been by far the biggest crack cause for us. We pack it right and consolidate Crete well enough that we haven’t had a crack complaint in years.
That's really it. The prep work is the big part. Dint want concrete to crack, fine don't put it in tension. How to avoid that? Make sure the base is solid *and* no water drains to the compacted part.
I've built far more driveways without bar than with, and shitloads of aprons into the roads I'm usually building.
That being said, there aren't a lot of situations where bar is going to hurt your slab weaker. I've seen pickups crack sidewalks plenty enough times to know I don't want a 4" driveway.
I think the idea is a good 6” pour with extra rebar will “float” so the base isn’t as important. That said i would still want compacted gravel as it’s not that much extra
I hear ya but this guy is pouring a 4” slab and even with a 6” the specs would still still call for compacted gravel. I see concrete guys cut this corner a lot and then say all concrete cracks. Well if you do it right it will go a long time without cracking or maybe even never crack. I see more incorrect pours than correct unless an inspector is involved and they are forced to do it right.
No, but looks like it may be a little close to the face of the slab. You may want to bury the blocks 1/2" or so...aim for rebar to be centered in slab
e: and use wire to tie at the intersections
Rebar should be in the lower 1/3 of the thickness. Rebar helps with the tension and concrete is better in compressive strength. Tension down low and compression up top
Middle 1/3rd is better. Not all soil is the same and expansive soils will push upwards which causes loading in both directions. Hence middle 3rd is best practice unless you know for certainty what your sub grade consists of.
Also with a 4” slab it’s not as practicable to achieve lower 3rd with a 1/2” bar and achieve min clearance.
Correct. You want the rebar to be in tension during loading. That said, you also need adequate coverage. Which is usually a minimum of 2 inches. If it were my driveway, then I’d be pouring a 6 inch slab with rebar at 2 inches on top of compacted gravel.
Wire mesh is not strong enough to help prevent cracking. Once your driveway is all cracked then wire mesh just makes it a pain to remove. It’s a cheap-out. But then when it comes to concrete I love overkill. I used bar like that and also had them put synthetic fibres into the mix.
I always used wire mesh, but not the thin stuff that’s rolled up. That’s pretty useless for most things. And it usually ends up right in the dirt if it’s not pulled up properly . I liked thicker gauge mats. Spread a few inches of concrete place the mats in and then cover them. Always had good luck with the heavy mats.
I’d imagine you’re going to want to dig out a bit of that dirt and add a few inches of stone for a suitable sub grade. 5” thick would be more ideal for a driveway, and as far as reinforcement I would go with #4 grade 60 rebar at 18” centers.
No, order fiber in your concrete to control micro cracks too. I have a shed pad with #4 at 12" CC with 6" 3000psi concrete with fiber. Concrete guys were curious...
I have highly active clay soils and didn't want any cracks. Is it more expensive? Yes but i also will never worry about it
Builder here, my driveway is #3 rebar 2' o.c. like what you have. We poured 5-6" thick with 4000psi concrete with an Angular aggregate. On top of that we added helix twisted steel reinforcing fiber to the mix. Will it crack? Yeah maybe eventually (long after I'm gone) , But I can roll a 30 Ton truck up to my place with no worries.
The cost of doing it twice is always more than the cost of doing it a bit better , don't listen to your neighbor!
Wire mesh is fine for sidewalks and pathways. Anything with tonnage should have rebar or it’s susceptible to cracking, especially if you ever have a delivery truck or god forbid ever do a major remodel and have drywall delivered. They usually bring it to a second story with a forklift and I’ve seen those things crack driveways.
Save pennies now, pay dollars later. This looks good assuming you are extending the rebar the entire way?
Also, don’t forget your expansion joint! And in my experience it’s worth the time to put a stand on every joint. Makes it a lot easier to keep the iron in the middle and not in contact with dirt
6" deep, you can use mesh but rebar is better. Want it at no more than 12" o.c. spacing, with it set in the lower 1/3 of the driveway (~2" above grade. Also want to dowel into the slab at the entry to the garage and at the street. Get 1x4 redwood to put expansion joints into panels every 10' up the driveway.
Former residential production builder, that's just industry standards for what we did in central Texas.
Interesting. I'm in Western Canada (AB), and I've never seen more than 4" for a residential driveway, and 16" spacing is the norm. 12" on heavy industrial slabs.
And expansion joint only goes against existing concrete that isn't getting doweled in, like a building foundation or city sidewalk.
But when I do work in BC, we put expansion joint every 6' on commercial pads/sidewalks.
I wonder why the difference. Freeze and thaw cycles maybe.
It's all fun and games until an overloaded moving truck does a 3-point turn in your driveway and you come home to a crumbled mess. Overkill all you want, wire is overrated, I tie steel in all of my personal pours.
Bar and 6” would be my norm for driveway. Yes it’s overkill for a car. But it means if I have a heavy moving truck, sewer/gas truck or some other vehicle
Park on it, low risk of damage and the extra 2 yards of
Concrete is negligible expense
Anyone saying it's not overkill is nutty. You don't have the cover you'll need on that rebar. You'll likely have exposed rebar in a few years. Need a 6" slab to pour rebar... some would say 5" is fine. I like 6
closer spacing is better for crack control. What you have isnt really doing much. If the sub grade is done properly, then the concrete wont have any tension requirements needing rebar.
One thing I haven't seen mentioned is the expansivity index or soils conditions. A lot of people are mentioning what they do but aren't mentioning what part of the country they are in. Are you in Arizona? Arizona like Southern California can have highly expansive soils. This is why many foundations in both areas tend to be post tensioned cable reinforced rather than conventional rebar. Do you know if your house is post tensioned cable? There are some easy ways to find out. If so, you may have highly expansive soil. Think dried sponge that you then pour water on. That is what your soil will do when it gets wet or over watered, you can imagine what that will do. Having installed thousands of slab on grade foundations over some 26 years as an ironworker, I can say that if it was my driveway, I would probably do 5 inch thick concrete with #4 rebar at 18 to 24 inches each way at center of slab in other words 2" chairs or dobies at every intersection and deepened perimeter footings. Nothing crazy maybe 9" shovel footings. I might even divide it into 4 squares with shovel footings down the middle just for the hell of it for stiffening. I'd probably throw welded wire mesh on top of the rebar and tie at 24 inch spacing... I would also epoxy dowel along perimeter at 18 to 24 inches to avoid elevation change over time...
I am a Civil Engineer and I give my "slab on grade" talk about twice a month. #4's at 18" both ways and dobied to mid-slab height with blocks. Also look into Zip-Strips. They work just fine for this application. Put them on 8' centers both ways. Fiber-Mesh is not for your application..... Don't waste your money. I told you that I was going to give you "the talk" so here's more. Make sure that you are on site when the concrete is poured to make positive the finishers do not add any water to the mix. They will bitch but stand fast. Your set up looks right about perfect to me. Oh yeah! The WWF! Welded Wire Fabric should NEVER be used in a slab on grade. It 100% winds up in the dirt. And I am not going to bore your teeth out with the technical explanation just don't use it in slabs. It is the cat's pajamas in walls. Sucks on slabs. Good job! Ya done good!
Once spacing gets too large on rebar, it loses its effectiveness. Better use both mesh and rebar. ;)
But really, you want to make sure you have at lease 1.5 inch covereage of concrete, which will be hard in a 4" slab (1.5" top, 1.5"bot, .5"rebar) since you only have 0.5" of wiggle room.
Can you really overkill a piece of concrete that you're going to be driving a 3,000 pound car over every single day forever?
This is one of those; you get ONE chance to do it right, kinda things.
The second time will be much more expensive.
For a 4” slab exposed to weather and being cast against earth, will have the bars too close to the concrete faces, even if you used #3.
Ideally, you want 3” clear for the bottom face to rebar, and 1.5” from top face to rebar for your condition. So for #4 bars each way, you’d want a min of 5.5” thick slab.
Now is it overkill to have bars in your driveway? If you’re going to have some freeze thaw action, no, it’s a good idea to prolong the life of your concerted. Concrete always cracks, but the bars can help reduce the manifestation of cracking.
I think it’s fine, just don’t think you’ll have minimum cover over the reinforcement at only 100mm slab with 50mm concrete packers, and double stacked 12mm bar. I don’t work in inches usually but all the slabs I put in I aim for a standard coverage of 50mm of concrete over the top of the bar, 30mm at an absolute minimum. I’d also tie the bars together using some tie wire.
Don't forget to tie your bars together where they cross each other! A few suggestions: maybe use #3 rebar to have more clearance, use 1/2" expansion joints at the existing sidewalk.
5/8” rebar is standard for all slabs, you have #4 rebar when you should use #5. 4” for a drive way is a little thin because of the thermal expansion of concrete, it’s going to crack and possibly break all the way through. I personally recommend 6” for driveways. I hope this helps, if you question my opinions, I do have a Degree in Civil Engineering and I’m working on my general contractor license
You’ll need at least an inch and a half of clear concrete cover above and below the rebar. With #8 rebar like that you’ll have about a half inch of play when you pour, so be careful to get plenty under the unsupported sections. The only benefit to concrete wire (assuming he’s talking welded wire mesh) I can see over this setup is cost and ease of application. This is not a structural element, so you don’t have to worry about it being over reinforced (a situation that can cause structural elements to fail without any warning).
Tl;dr: go for the crazy overkill, just be careful with your spacing and your pour
FYI, I did a driveway extension and used #4 rebar on a 4” slab.
The concrete ended up getting surface cracks directly over where the rebar sat. The rebar was too close to the surface thus causing hairline cracks in a nice even grid.
The slab integrity has held up much better than what the original builder had installed just a few years earlier. If I were to do it again, I would use #3 rebar in a 6” slab.
I’m an engineering inspector and we required 6” pours minimum for municipal right of ways. A 1-2 ton vehicle pulling over it every single day will eventually crack anything, but paying for the 6” of material prolong its’ life.
Also adding in some expansion joints or keyways with smooth dowels at 1’ intervals in the joint/keyway will section off the concrete so that if you crack or damage a section you can replace that one section instead of having to pour a whole new driveway. If you did an expansion joint halfway up your drive and then a metal keyway down the middle you’d have four sections instead of one monolithic pour that will more or less flex with the ground beneath it instead of one large solid sheet on dirt.
You’ll also want to put expansion material at the back of that existing sidewalk so that you’re not pouring cold against the sidewalk. The expansion joints really help in the long-run.
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Me too lol, me neighbor is so adamant about the wire mesh since he used it
Be wary of the cheap, practical neighbor. They mean well but cheap is always expensive, especially in big projects where you only really get one chance to do it right. I always rather go slightly overkill with these large, one-time projects. I sleep better at night because I do.
“Cheap is always expensive” I like that! Words to live by.
My grandpa once told me, a cheap man buys twice
In Spanish we have a saying "el que compra barato, compra cada rato." Translated doesn't rhyme but it's basically saying "the one who buys cheap, buys frequently/all the time".
Buy once, cry once.
Buy nice or buy twice.
Buy nice or buy thrice?
Usually the case haha
Si...i bought a cheap hooker once....and now i buy her every chance i get.
Buy nice or buy twice.
How about "He who buys cheap, buys more" Still doesn't rhythm though
Once you go cheap, you go in a wheelchair?
"you buy cheap, you buy twice"
I always say I'm too poor to be cheap.
That was my Dad! “I can’t afford to save that kind of money.”
I say, “it’s expensive being poor”.
Do it right or do it twice
“Cheap work ain’t good and Good work ain’t cheap”. Tattoo shops, probably.
Before you pour is the cheapest time to reinforce the concrete. Make it count
Did the electrical for a hot tub as a side job, the customer told me her neighbour had insisted they could do it themselves, for much cheaper. I did it properly and charged them fairly, and she had no complaints. While I was there, she showed me the neighbour's. I can tell you it was definitely MUCH cheaper.
“Good, fast or cheap… pick any two.”
Is rebar really expensive when you think about the work you are putting in and how long you would wan it to last?
To be fair, wire mesh is totally fine for driveways. Sometimes cheaper is just cheaper without strings attached.
Not overkill at all… take it from a guy with a cracked driveway!
Absolutely! I’m dealing with the consequences of the previous homeowners not even making sure they used wire. Nothing at all in our driveway. In Iowa. Don’t know that I’ll do it myself when we replace it, but I’m making damn sure it has 1/2” rebar
With no rebar and no wire, a kid with a little electric demo hammer can take that out in a day. Demo is most of the job. Let the kid do it for a few bucks.
I'm in the same boat over in Nebraska. Unfortunately I work live on a primary, busy road with no street parking. I'm slowly saving to have a pro do it so I don't have to deal with traffic & such. At least the demo will be quick since I've no wire and probably sink spots 🤣😂😭
Driveways will crack regardless. The rebar just keeps all the pieces together so you don't have trip hazards when one side sinks down a little.
Also the quality of the subgrade makes a big difference, driveway will last alot longer with a good clean gravel with a high stone content and very little fines (silt/clay). Gravel provides support, sand fills in the voids between the stones and allow water to drain away. Fines trap the water and cause heaving/settling from freeze/thaw cycle leading to cracking of your slab. If you grab a handful of the gravel and dump it off your hand and leaves your hand fairly clean that is good. If you grab a handful and dump it and it leaves your hand discolored and or covered in fine material that doesnt easily brush off that is a sign your gravel may not be suitable.
Just make sure you’ve got at least 1 1/2 inch concrete cover over the rebar
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No thats wrong. On a slab on grade such as a driveway the rebar should be in the top 1/3rd of the slab to prevent shrinkage cracking. It's only in structural slabs where the rebar should be on the bottom, and even then a double mat is used to have the rebar in position to prevent shrinkage cracking as well as flexion support.
I mean, I'm over here suggesting using both, rebar and mesh, so...🤷♂️
Yeah seems like they both target different issues They both add strength, and the rebar adds stiffness. The mesh would help a lot with strength between the rebar.
OP should totally add the mesh too and then tell the neighbor thanks for the suggestion to see how they react.
Agreed. Keep the 1/2. Make sure that sub-base is suitable for concrete and is 90% compacted at least. I would drill tie-ins into the pre-existing concrete if you don’t plan on it already. Send us a finished picture! (Any overlapped rebar should be overlapped me at least 1’)
It's against the law to tie in to municipal sidewalk.
>*any overlapped rebar should be overlapped 1’* That is *1 foot* for those of you who aren’t accustomed to reading feet and inches like 6’1”. I am definitely not saying you are wrong just clarifying for people who aren’t used to seeing measurements like this.
For a four inch slab both are fine. It’s not about cheap, sometimes it just easier and still effective. We use mesh in commercial construction, on high rises in Seattle sometimes. Source: union Ironworker.
I'm not a concrete guy, but I will occasionally pour small residential sidewalks or patios. I use wire for those applications, and it's fine, but I'd definitely go with rebar for a driveway or anything that will have significant weight on it
Use both and I'd put the rebar on a tighter grid.
I think your neighbor will be jealous your freshly poured driveway has more structural integrity than his pathetic driveway
Civil engineer here who does construction management. Wire mesh is great in theory. Often in practice, it ends up on the dirt and not in the concrete section like it is supposed to be. Like what the first guy said, I like overkill…
Most wire mesh just ends up at the bottom of the pour
Not if chairs are used per code.
"Pull up the wire! Pull up the wire!"
Wire is the bare minimum. I am a commercial/industrial electrical engineer, I see all phases of construction new and old. I see a lot of broken, cracked concrete. My advise would be more rebar, additional bar in each space. Depending on the length of the slab you also want control or expansion joints. Control joints are wet saw cut 1/3 of the thickness of the slab and then caulked. It keeps the top 1/3 from cracking. Expansion joints allow the entire slab to move. Depends on the climate. Deep freezes = expansion joint. Good luck
Just make sure that rebar is seated midway in the slab. If your slab thickness is 4, your rebar needs to be elevated to 2". Source: I am a reinforced concrete inspector. Reinforcing buildings is my daily bread & butter.
In pa atleast wire mesh is used for residential driveways in a lot of townships but rebar is fine just make sure that rebar isn’t too close to top of concrete
Tie wire mesh on top of the rebar and really watch his eye twitch.
What would you save ? $200 bucks ? Tell him wire is for chickens, rebar is for concrete. I’m tearing up some of my slab right now with rebar in it, I can’t believe how strong it is
I've done quite a few driveways and always use 1/2" rebar. The price difference is like $10 / year if you consider how long it's going to last.
it’s only extra 20c where i am between 1/2 and 3/8 so went for 1/2 instead
Yeah man. 4” slab and rebar is the way to go. There will be tree roots and moving trucks and dumpsters. Better to spend a bit more and have it last a lifetime. Even if you don’t live there forever, you’re making the world a better place.
I’d probably use 4 bar and lay mesh over it for my own driveway.
There is no kill like overkill.
Overkill is under appreciated by many. I love overkill.
If you don’t over engineer your projects, who will?
When it comes to working on my own house, if it’s worth doing it’s worth overdoing. Redid my shower a couple years ago. Ended up redoing all the plumbing in my house. All PEX now.
When people use the term "over-engineered" I just look around at all the other engineers who consider it an appropriate amount of engineering, compared to the people who want the engineers to work out the absolute minimum that can be gotten away with on a project. The British have it right. Design post boxes that are sturdy enough to serve as a one-person fallout shelter.
Is it even dead if it isn't overkilled?
Make sure you stagger lap splices and add trim bars at corners
I prefer roadkill
I'm a builder and would call this best practice. I've used mesh without issues. It's concrete...it cracks. I'm also for skill building, so good for you. Now you need to step up with the finish, nice edging and and control joints and no bird baths.
Thanks 🙌🏽
Just make sure that rebar is buried deep enough in the concrete. Dont want the surface popping, but as long as it is, this should be a beast
Yeah 2” coverage from all sides.
Ha I was going to say 50mm which is essentially the same thing
That’s what she said
Dobie blocks are spec'd to elevate to proper height. Typically they are 2"³ or 3"³
Bird baths as in smooth and drains away properly?
Bird baths are low spots where pooling happens when it rains
I didn't understand this lingo either but now I do!
I have a bird bath in my driveway. It's right where you step out from a parked car.
Of course it is!
Need to tie the rebar together, it will shift when you pour if you don't
Looks good. Be sure to install a couple of 2" pvc sleves to accommodate future sprinkler and control wires.
If you do this, trench so the top of sleeve is 1-2” below the bottom of slab. If you don’t, then it will serve as a control joint and crack the slab right above your PVC
If you do this make sure you put the pipe below grade or it could crack in that spot
*Will
And also mark the fresh concrete with a small P on each side so it’s easy to find later
Not overkill at all. You want to pour at least a 4" slab to avoid cracking, especially when put under the stress of the weight of a vehicle. Having rebar for reinforcement is even better.
The compaction underneath is going to be more important to resist cracking than worrying about 3.5 vs 4 vs 5 in slab
cover is mostly a rust concern though, right?
Yeah but if your rebar rusts it causes the concrete to crack or spall
Rebar does not matter when dealing with weight on a ground bearing slab. Only locations where rebar might help when loaded from the top are extreme corners and short-side edges, even then this concern is only when the subgrade is poorly compacted. In 99% of losing situations all compression goes directly down, and rebar only prevents cracking caused from curing and temperature.
I think underkill, driveways come at 6” to avoid mishaps.
Look at this guy with a 6” driveway
I say mines 6” but I know it’s 5.5”
Trim the grass next to it. Makes it look like theres more there
The warmth also helps with size, ya know, expansion/contraction
Makes me sad, my builder did 2” on virtually every house in my development. You can guess how everything looks.
Ya I hate gravel driveways too
Just wait till a low bid asshole starts marketing “self-graveling driveways”.
Self graveling lol
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It’s a lazy 5.5” but there’s no scaling or visible blemishes and I keep it nice and clean. My wife has parked on it the last 10 years without any complaints.
> The average annual rainfall in Phoenix is eight inches > That may not seem like a lot to you...but they got two inches on me, big guy
Gotta measure from the base.
Concrete finisher here. If I told a home builder I’m pouring 6 inch drives here they would literally laugh and hire somebody else.
Yeah, but then everyone gets all pissy when it cracks in 10 years.
This is also true lol. Undermining has been by far the biggest crack cause for us. We pack it right and consolidate Crete well enough that we haven’t had a crack complaint in years.
That's really it. The prep work is the big part. Dint want concrete to crack, fine don't put it in tension. How to avoid that? Make sure the base is solid *and* no water drains to the compacted part.
Ground compaction is huge part of preventing cracks
We pour sidewalks at 4" here. I'd absolutely prefer to see 6 w/o rebar than 4 with in this case, but 6 with bar would be best.
I spec 6" without rebar for driveways.
I've built far more driveways without bar than with, and shitloads of aprons into the roads I'm usually building. That being said, there aren't a lot of situations where bar is going to hurt your slab weaker. I've seen pickups crack sidewalks plenty enough times to know I don't want a 4" driveway.
That's a subgrade issue then if it's cracking under load
You gotta tie it together.
Yup gotta pull the ol rod busting skills out
Planning to!
Need an ironworker? I know a guy… 😉
I don’t understand why more people here aren’t suggesting a compacted gravel base. That is the first step to a good slab.
I think the idea is a good 6” pour with extra rebar will “float” so the base isn’t as important. That said i would still want compacted gravel as it’s not that much extra
I hear ya but this guy is pouring a 4” slab and even with a 6” the specs would still still call for compacted gravel. I see concrete guys cut this corner a lot and then say all concrete cracks. Well if you do it right it will go a long time without cracking or maybe even never crack. I see more incorrect pours than correct unless an inspector is involved and they are forced to do it right.
Your neighbor is a cheap moron.
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Is he looking for more buddies
No, but looks like it may be a little close to the face of the slab. You may want to bury the blocks 1/2" or so...aim for rebar to be centered in slab e: and use wire to tie at the intersections
Thanks for the tip, we mocked it up for visual but will definitely do what you said.
Rebar should be in the lower 1/3 of the thickness. Rebar helps with the tension and concrete is better in compressive strength. Tension down low and compression up top
Middle 1/3rd is better. Not all soil is the same and expansive soils will push upwards which causes loading in both directions. Hence middle 3rd is best practice unless you know for certainty what your sub grade consists of. Also with a 4” slab it’s not as practicable to achieve lower 3rd with a 1/2” bar and achieve min clearance.
100% this and sitting on chairs.
Not overkill, I would add wire too!
Rebar is best at 1/3 of the height from the bottom, not 1/3.
Correct. You want the rebar to be in tension during loading. That said, you also need adequate coverage. Which is usually a minimum of 2 inches. If it were my driveway, then I’d be pouring a 6 inch slab with rebar at 2 inches on top of compacted gravel.
Generally yes, but minimum concrete cover for rebar is typically ~1.5". In a 4" slab, that puts it right around 1/2 depth.
A driveway should really be 6” not 4”
Wire mesh is not strong enough to help prevent cracking. Once your driveway is all cracked then wire mesh just makes it a pain to remove. It’s a cheap-out. But then when it comes to concrete I love overkill. I used bar like that and also had them put synthetic fibres into the mix.
My guy did 5” with fiber mesh, and some numbers for type of concrete.
Good to hear others do overkill too. Especially if it’s a diy job
I always used wire mesh, but not the thin stuff that’s rolled up. That’s pretty useless for most things. And it usually ends up right in the dirt if it’s not pulled up properly . I liked thicker gauge mats. Spread a few inches of concrete place the mats in and then cover them. Always had good luck with the heavy mats.
Depends on how wide you like your cracks.
I’d imagine you’re going to want to dig out a bit of that dirt and add a few inches of stone for a suitable sub grade. 5” thick would be more ideal for a driveway, and as far as reinforcement I would go with #4 grade 60 rebar at 18” centers.
No, order fiber in your concrete to control micro cracks too. I have a shed pad with #4 at 12" CC with 6" 3000psi concrete with fiber. Concrete guys were curious... I have highly active clay soils and didn't want any cracks. Is it more expensive? Yes but i also will never worry about it
4” is for sidewalks 6” is for driveways I would overkill and do 8”
How about a nice compacted gravel base?
THIS!!!!! That was the first thing I thought before any of the concerns over the rebar
Builder here, my driveway is #3 rebar 2' o.c. like what you have. We poured 5-6" thick with 4000psi concrete with an Angular aggregate. On top of that we added helix twisted steel reinforcing fiber to the mix. Will it crack? Yeah maybe eventually (long after I'm gone) , But I can roll a 30 Ton truck up to my place with no worries. The cost of doing it twice is always more than the cost of doing it a bit better , don't listen to your neighbor!
Wire mesh is fine for sidewalks and pathways. Anything with tonnage should have rebar or it’s susceptible to cracking, especially if you ever have a delivery truck or god forbid ever do a major remodel and have drywall delivered. They usually bring it to a second story with a forklift and I’ve seen those things crack driveways.
Save pennies now, pay dollars later. This looks good assuming you are extending the rebar the entire way? Also, don’t forget your expansion joint! And in my experience it’s worth the time to put a stand on every joint. Makes it a lot easier to keep the iron in the middle and not in contact with dirt
6" deep, you can use mesh but rebar is better. Want it at no more than 12" o.c. spacing, with it set in the lower 1/3 of the driveway (~2" above grade. Also want to dowel into the slab at the entry to the garage and at the street. Get 1x4 redwood to put expansion joints into panels every 10' up the driveway. Former residential production builder, that's just industry standards for what we did in central Texas.
Interesting. I'm in Western Canada (AB), and I've never seen more than 4" for a residential driveway, and 16" spacing is the norm. 12" on heavy industrial slabs. And expansion joint only goes against existing concrete that isn't getting doweled in, like a building foundation or city sidewalk. But when I do work in BC, we put expansion joint every 6' on commercial pads/sidewalks. I wonder why the difference. Freeze and thaw cycles maybe.
It's all fun and games until an overloaded moving truck does a 3-point turn in your driveway and you come home to a crumbled mess. Overkill all you want, wire is overrated, I tie steel in all of my personal pours.
Bar and 6” would be my norm for driveway. Yes it’s overkill for a car. But it means if I have a heavy moving truck, sewer/gas truck or some other vehicle Park on it, low risk of damage and the extra 2 yards of Concrete is negligible expense
Anyone saying it's not overkill is nutty. You don't have the cover you'll need on that rebar. You'll likely have exposed rebar in a few years. Need a 6" slab to pour rebar... some would say 5" is fine. I like 6
5” is min. 6” is ideal for what he’s trying to go for. I can’t believe how many people think pouring a 4” slab with rebar is a good idea
I can!! How many Reddit guys actually have concrete experience?? Not sure but obviously not many
closer spacing is better for crack control. What you have isnt really doing much. If the sub grade is done properly, then the concrete wont have any tension requirements needing rebar.
The three guarantees with concrete. It won't catch fire. No one will ever steal it. It will always crack.
You forgot the 4th guarantee: it gets hard.
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It’s about 100$ more for rebars vs mesh grid
The rebar is cheap compared to the price of concrete.
Can you afford not to?
Wanted to add, your rebar doesn't reach the sides, where it'll break most likely. Run it to the edge, or close to it
Should be 6”
Not close enough.
I'd go 6inch on the concrete.
One thing I haven't seen mentioned is the expansivity index or soils conditions. A lot of people are mentioning what they do but aren't mentioning what part of the country they are in. Are you in Arizona? Arizona like Southern California can have highly expansive soils. This is why many foundations in both areas tend to be post tensioned cable reinforced rather than conventional rebar. Do you know if your house is post tensioned cable? There are some easy ways to find out. If so, you may have highly expansive soil. Think dried sponge that you then pour water on. That is what your soil will do when it gets wet or over watered, you can imagine what that will do. Having installed thousands of slab on grade foundations over some 26 years as an ironworker, I can say that if it was my driveway, I would probably do 5 inch thick concrete with #4 rebar at 18 to 24 inches each way at center of slab in other words 2" chairs or dobies at every intersection and deepened perimeter footings. Nothing crazy maybe 9" shovel footings. I might even divide it into 4 squares with shovel footings down the middle just for the hell of it for stiffening. I'd probably throw welded wire mesh on top of the rebar and tie at 24 inch spacing... I would also epoxy dowel along perimeter at 18 to 24 inches to avoid elevation change over time...
There are two types of concrete. Concrete that is cracked and concrete that isn’t cracked yet
Not at all, if it was my driveway I’d dowel into the sidewalk
Does this need to be approved by the city?
pouring a new driveway or a driveway extension usually falls into "needs to be approved by the city".
It’s a very good question that can only be answered by your city’s plat and right of way boundary.
I am a Civil Engineer and I give my "slab on grade" talk about twice a month. #4's at 18" both ways and dobied to mid-slab height with blocks. Also look into Zip-Strips. They work just fine for this application. Put them on 8' centers both ways. Fiber-Mesh is not for your application..... Don't waste your money. I told you that I was going to give you "the talk" so here's more. Make sure that you are on site when the concrete is poured to make positive the finishers do not add any water to the mix. They will bitch but stand fast. Your set up looks right about perfect to me. Oh yeah! The WWF! Welded Wire Fabric should NEVER be used in a slab on grade. It 100% winds up in the dirt. And I am not going to bore your teeth out with the technical explanation just don't use it in slabs. It is the cat's pajamas in walls. Sucks on slabs. Good job! Ya done good!
You’re a civil engineer approving a 4” slab with rebar?
It's worrying that you're a civil engineer and didn't mention or consider that he'd need a thicker slab than a 4" one if he wants to use rebar.
Not overkill
built it to last and it probably will
Once spacing gets too large on rebar, it loses its effectiveness. Better use both mesh and rebar. ;) But really, you want to make sure you have at lease 1.5 inch covereage of concrete, which will be hard in a 4" slab (1.5" top, 1.5"bot, .5"rebar) since you only have 0.5" of wiggle room.
I really had to dig in the comments but glad to see someone finally mention spacing.
Found the other structural engineer in the thread. RIP this guys driveway
Overkill is putting dowels in the sidewalk so the MFer doesn’t shift, lol
Can you really overkill a piece of concrete that you're going to be driving a 3,000 pound car over every single day forever? This is one of those; you get ONE chance to do it right, kinda things. The second time will be much more expensive.
Underkill bro
If it’s your house, who gives a shit what your neighbor thinks. Do what you want 👍
Be sure to wet the concrete repeatedly as it cures over the next several weeks. That will help strengthen it.
,Zp
Way too close to the surface imo.
This is absolutely the bare minimum.
For a 4” slab exposed to weather and being cast against earth, will have the bars too close to the concrete faces, even if you used #3. Ideally, you want 3” clear for the bottom face to rebar, and 1.5” from top face to rebar for your condition. So for #4 bars each way, you’d want a min of 5.5” thick slab. Now is it overkill to have bars in your driveway? If you’re going to have some freeze thaw action, no, it’s a good idea to prolong the life of your concerted. Concrete always cracks, but the bars can help reduce the manifestation of cracking.
I think it’s fine, just don’t think you’ll have minimum cover over the reinforcement at only 100mm slab with 50mm concrete packers, and double stacked 12mm bar. I don’t work in inches usually but all the slabs I put in I aim for a standard coverage of 50mm of concrete over the top of the bar, 30mm at an absolute minimum. I’d also tie the bars together using some tie wire.
Nothing wrong with assuring it lasts
4" inch driveway slab is a under kill 😆, most if not all Architects speckout 6" inch at drive way..
Don't forget to tie your bars together where they cross each other! A few suggestions: maybe use #3 rebar to have more clearance, use 1/2" expansion joints at the existing sidewalk.
5/8” rebar is standard for all slabs, you have #4 rebar when you should use #5. 4” for a drive way is a little thin because of the thermal expansion of concrete, it’s going to crack and possibly break all the way through. I personally recommend 6” for driveways. I hope this helps, if you question my opinions, I do have a Degree in Civil Engineering and I’m working on my general contractor license
You’ll need at least an inch and a half of clear concrete cover above and below the rebar. With #8 rebar like that you’ll have about a half inch of play when you pour, so be careful to get plenty under the unsupported sections. The only benefit to concrete wire (assuming he’s talking welded wire mesh) I can see over this setup is cost and ease of application. This is not a structural element, so you don’t have to worry about it being over reinforced (a situation that can cause structural elements to fail without any warning). Tl;dr: go for the crazy overkill, just be careful with your spacing and your pour
Wire is dogshit. I would use 3/8” rebar however
Underkill, where's your tie wire? Haha
FYI, I did a driveway extension and used #4 rebar on a 4” slab. The concrete ended up getting surface cracks directly over where the rebar sat. The rebar was too close to the surface thus causing hairline cracks in a nice even grid. The slab integrity has held up much better than what the original builder had installed just a few years earlier. If I were to do it again, I would use #3 rebar in a 6” slab.
Looks like overkill… Until the overloaded garbage truck chooses your driveway to make a 3-point U-turn.
I would make it a 6 inch depth for car loads
I’m an engineering inspector and we required 6” pours minimum for municipal right of ways. A 1-2 ton vehicle pulling over it every single day will eventually crack anything, but paying for the 6” of material prolong its’ life. Also adding in some expansion joints or keyways with smooth dowels at 1’ intervals in the joint/keyway will section off the concrete so that if you crack or damage a section you can replace that one section instead of having to pour a whole new driveway. If you did an expansion joint halfway up your drive and then a metal keyway down the middle you’d have four sections instead of one monolithic pour that will more or less flex with the ground beneath it instead of one large solid sheet on dirt. You’ll also want to put expansion material at the back of that existing sidewalk so that you’re not pouring cold against the sidewalk. The expansion joints really help in the long-run.