I'd say it was a bid from someone who really wanted the job & was
proabably going to skimp on the details.
I would suggest writing up (or obtaining) at least some sort of simple
specification for the prep, base, rebar (size & placement) & concrete
(w/c ratio, strength) . Also some words about the finishing & quality
of the result.
IMO 4" is was too thin & I'm not a huge fan of unreinforced thicker
I would go with #5" min with #4 @ 18" both ways ......I hate jagged,
uneven cracked slabs.
I like them to crack in the control cuts :)
I'll probably catch some flak from the guys who don't like rebar in
thin slabs (they insist it does no good)
My experience is that it holds the pieces together
You're getting ready to spend a fair chunk of $'s.........how do you
want the result to look in a few years?
3" is the current accepted minimum for concrete cover over/under rebar,
right? That's a 6.5" slab. You're really good at spending this guy's
I'm curious why he needs a 14' wide driveway. Maybe so two cars can
pass? I'd go with a narrower driveway for the bulk of it and a couple
bump outs* to allow passing. It'd be a lot cheaper.
* I got a laugh out of that one. Firefox's spell checker flagged
bumpouts as incorrect, and gave me the choice of bump outs or bum
pouts. Bum pouts?! Has anyone in the history of the English language
ever combined bum and pouts??? Methinks not.
I agree that 14' seemed a bit wide for a 300' driveway.....the house I
sold last year had a 15' driveway but it was only 65' long....more of
an extended parking area.
In this case maybe a narrower drive with "bum pouts" & an enlarged
parking area....the material saved could go thicken the slab
I believe that cover requirements (& have had success with) are 3" for
soil contact & 2" elsewhere. so that would be 5.5". Unless they've
Yeah, I'll admit I'm good at spending money BUT it all depends on what
the guy wants preformance wise. Is he going to be disappointed when
the slab cracks (not in the cuts) AND shifts levels? And he's got
cracked up mess
If not, go thin but otherwise the 5.5 to 6" ain't that much more
material cost over the suggested 5" min. The extra concrete & rebar
wiil add a few thousand $'s to the job & (IMO) greatly enhance the long
term performance of the slab.
Soil condtions & weather could have major effects on the slab (I don't
the local conditons in Eureka, TX) but in SoCal they're generally mild.
RIco did you get the post base photos, I sent last week?
A minor correction to your calculation:
3" clear for the soil + #4 each way (= 2*5/8 OD) + 2" clear from top
= 6-1/4". I would use a minimum slab thickness of 6-1/2"
And this assumes that no salt for de-icing is used on the driveway. If
salt is to be used, then the top cover should be increased to at least 3
inches and even that is going to rust eventually. So, if salt is to be
used then add the cost of epoxy coating the rebar to the cost of the
Boy, talk about spending other people's money! We sure can add it up fast.
Bob Morrison, PE, SE
R L Morrison Engineering Co
Wide loads maybe?
Another option to cut costs, though it's a bit of an older look, would be
to pour "strips" on each side of the driveway. Maybe 2 feet wide on each
side. Vehicle tires usually don't run down the middle of the driveway, so
you could save money by not filling the center with concrete. Pour the
strips, and place gravel or grass in the center and on each side. You could
always upgrade later and fill the center areas with concrete as time and
Just a thought...
What the hell are you saying, Bob?! Anthony _sucks_ at spending other
people's money. We're going to have to get the smoking jacket back and
change the secret handshake again... ;)
When I lived in New Orleans about ten years ago, they upgraded
Tchoupitoulas. Major truck route following the river. Obviously they
have problems being on silty sand with an extremely high water table,
so they couldn't prepare a BMOC (Bob Morrison Official Compacted) base.
They designed the concrete road bed as a beam. The amount of concrete
and rebar in that slab was astounding. I'd tease the guys working by
pointing out that retaining walls were supposed to be _vertical_.
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. ;)
I disagree. I've seen that done. The end result looks like a
patched up mess. If you can't do it right, I suggest you just put
down some gravel until you can do it right.
BTW, all driveways around here are 4" thick including mine and
though it be 30 years old, is not broken up. #4 rebar 24" ew oc
chaired on pour. Matter of fact, you won't find a crack in it.
At 14' wide, the concrete needs a saw joint down the center and
cross cuts every 7 to 10 feet. There will be a lot of lineal
expansion in 310', I would use expansion every 60'. The rebar is
OK, but 4" is minimal. There should be a minimum of 1 1/2" cover
on rebar, making 1/2" bar almost too big to cover with 4". Money
is better spent on subsoil preparation and drainage.
$3 would be low in central Oklahoma, but our stone is all
Keep the whole world singing. . . .
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
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.
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