Cost of concrete driveway

[carolyn]

I would definitely include the subgrade and crack control joints. Except maybe for a home made concrete patio stone. :)

Thanks for the information. I appreciate the knowledge.

Carolyn

[HerHusband]

Rico,

:) OK, well how about a 6" compacted gravel base, and a layer of concrete pavers? That's bound to cost more than just concreting the whole drive? It would look nice too...

Anthony

[RicodJour]

Better. If you'd said a compacted base, concrete slab on top, some tumbled travertine pavers, and radiant snowmelting (bonus points if the driveway is in Florida) I'd forgive you and email you the new secret handshake instructions. It's a wee bit more complicated than the one you knew. It'll help if you're double-jointed. Take some pain meds while you're learning it. ;)

R

[Matt Whiting]

Yes, but I'm still surprised the rebar adds so little additional strength. I guess being nearly on the neutral axis is probably the killer.

Matt

[RicodJour]

That's the whole point about rebar in driveway and other slabs. People view rebar as a panacea - that it's a simple way to make a slab far stronger, and it's not. At least not the way it's usually done, and not the way it can be done in thin slabs on grade.

R

[Jonny]

Central Texas. Non union laborers. Suspect some were not documented non-native American workers. Small commercial company that normally does roadwork and such for commercial parking lots and slabs, and county roadwork.

Driveway is same 14' wide. 159' long. Also included adding a graduated entry from garage doorway tied to garage slab, personnel entry door landing tied to garage slab, a small sidewalk from that to the driveway some 10' long. 3/8 rebar every 12". No chairs. Beams on edge were 12" thick. 7" thick remainder. 3" of roadbase over stable Texas Hill country soil (gravel/rock/gray clay). Full apron at street tie-in. Apron drainage horizontally aligned with road frontage drainage, no culvert. Expansion joints every 10' made from #1 cedar 1X4s. All boundary edges were rounded. Included all flatwork. Surface is provided with purposely placed lines across the driveway for traction and drainage. Natural water course is across the driveway. Cost was a hair over 5K. The driveway was meant a roadway to the garage, not the house.

The remainder of driveway is strictly compacted roadbase, which forms a circle in front of the house. The center of the circle contains the septic tank. The septic boundary is in large rock surface man-made (me) formation. My sons compacted the roadbase with their loaded pickup trucks while it was wet last summer. Had to wet it down twice. They went over the course for over and hour. Had to get another load of roadbase as they mashed it down so well the first time. 3" PVC-UV under one area 5' from concrete driveway edge termination to allow drainage under straight roadbase area. Bermuda grass seems to like the roadbase, weeds don't. I'll get over it.

[HerHusband]

I'm no engineer, but wouldn't the rebar help control cracking and just hold things together when it does crack?

I'm probably wrong, but I would think the slab could settle unevenly if it cracked without the rebar, whereas it might stay a little more stable with the rebar?

In any case, rebar is cheap, so I've always added a couple of bars in the sidewalks and stuff we've poured. It usually only added an extra $10 or so to the total cost, so why not?

Anthony

[Bobk207]

I agree with you about rebar holding things together when it does crack but this drivway is pretty big

If it has rebar @ 18" oc (both ways) we're talking about 6000 ft of rebar....... so buying & placing the stuff would take some $'s.

IMO worth it, but others disagree

cheers Bob

[butwhat]

I put rebar in everything. Did anybody recommend a mix? I'm also curious as to what effect a driveway mat under the concrete would have. A friend of mine uses them to drive semis over. He swears by the road mats. I usually try to put down 12" of clean rock covered with visqueen for a drainage base.

[Bob Morrison]

You got it. The effective "d" for a 6-1/2 inch slab on grade is only

3-1/4". Not to mention that #4 @ 18" o/c is a pretty small amount of steel.

[Bob Morrison]

Anthony:

Yes the rebar does hold things together when they crack (and it will crack). However, if there is no where for the slab to deflect then the cracked sections will stay together just fine.

However, the point of proper subgrade preparation is to prevent differential settlement by making the base consistent so the slab does not have to span any distance.

As I said before I regularly specify unreinforced slabs: no rebar, no welded wire fabric, no fibermesh, just plain concrete. These slabs perform just fine if the contractor takes the time to properly prepare the gravel base and subgrade. And as for gravel base I specify 3/4" minus compacted crushed rock, not pea gravel.

Elevated slabs are another matter and are not what is being discussed here.

[Bob Morrison]

12" of rock is a pretty substantial base. Unless you are on very soft ground I think you could eliminate any visqueen or geotextile fabric and still get excellent slab performance.

Remember that no matter what you do the slab will crack. so, put in crack control joints. At least then it will crack in a straight line.

[Bobk207]

Bob-

For the 14' driveway under discussion, if you spe'd 5" unreinforced.... what spacing would you spec for crack control joints?

Would you go the full 14' width with no joint? A spacing of 7' (across th4e width) is kinda short but 14' seems a little far.,

cheers Bob

[Bobk207]

Bob-

Agreed the "d" is really small but i think other factors are at work & the rebar wards them off......kinda like a rabbit's foot. :)

cheers Bob

[Bob Morrison]

My spec for crack control joints reads:

Crack control at max 150 sq ft and max aspect ratio of 1.5:1

So, a joint pattern of 10x14 (140 SF) with an aspect ratio of 1.4 fits within the parameters. You could probably get away with 12x14, but that may be pushing it a bit. This is one of those things where more is better.

The joint is a 1" min deep sawcut or tooled joint. Some people like to use vinyl strips, but it is hard to get them straight. Sawing of joints should be done as soon as the slab is hard enough to walk on with out leaving a mark. The new lightweight joint saws are waterless and look something like a gas powered lawn edger.