Bricks, Masonry, Asphalt and Concrete - driveway addition

I am trying to figure out how many yards of concrete i would need to widen my driveway. the shape is like a triangle. the top area is 21ft wide the bottom is 11ft wide and the lenght is 56ft long.

also do you think a 4" deep slab will be good enough for a driveway???

You have a trapezioid shape. Average the 11' and 21' dimensions, multiply by the 56' and 0.3333' for the 4" slab and divide by 27 cubic feet per cubic yard, or

(11' + 21')/2 x 56' x 0.3333'/27 = 11.06 cy

With the right subbase, design mix and rebar, depending on ground conditions, 4" should be fine for a driveway.

Originally posted by bungalow jeff
You have a trapezioid shape. Average the 11' and 21' dimensions, multiply by the 56' and 0.3333' for the 4" slab and divide by 27 cubic feet per cubic yard, or

(11' + 21')/2 x 56' x 0.3333'/27 = 11.06 cy

With the right subbase, design mix and rebar, depending on ground conditions, 4" should be fine for a driveway.


and remember to order an extra yard (just cus). Our driveways are done with 2X4's so they are 3.5 inches. it seems to work fine. Just order 12 yards and you should be good to go

4" is a standard dimension for sidewalks and light duty pavements, however 3.5" for a driveway should be fine too, unless you are driving home in the company tank.

Originally posted by bungalow jeff
4" is a standard dimension for sidewalks and light duty pavements, however 3.5" for a driveway should be fine too, unless you are driving home in the company tank.

so what do you use for forms?

Usually planks are used, so slab depth is not a factor. Driveway curb cuts in NYC use 7" slabs to allow for trucks.