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estimating concrete to fill 8" block

GCNC's picture

Hi all

Anyone have the formula to estimate the amount of concrete needed to fill a 8" block wall. I have heard that 1 yd for every 100 sq ft for 12 " block so I can ball park it but it would be nice to be sure.


(post #96616, reply #1 of 5)

just calculate it has a concrete wall. you will have some waste but depending on how much block you filling the. waste and minimum order is real close. Its not worth waiting on a half yard.

(post #96616, reply #2 of 5)

Depends on the blocl. Each manufacturer uses different wall thicknesses, web sizes/quantities, etc.  Get a hold of your supplier- they most likely have a figure for you.

Our block usually have two cores at 6" x 6 1/2" each. That's 78 sq in of the 128 sq in profile, or just over 60% hollow.  Given that 1 cy of concrete yields just about 40 SF of 8" concrete wall, 40/.6 = 66.7 SF/CY  for core fill.  So, I usually figure 1 CY per 60 SF of wall, to allow for waste.  As Brownbagg said- nothing like sitting around waiting for a 1/2 yard load at 5 pm.


Edited 11/13/2004 10:16 am ET by BobKovacs

"Brilliance!! That's all I can say- Sheer, unadulterated brilliance!!" Wile E. Coyote- Super Genius

(post #96616, reply #3 of 5)

hc.. also.. make sure you spec a "grout " mix.. it's pretty hard to get conc. to flow  and fill all of the voids..

 if you really want to fill all of the voids.. you might want to think about  batching it on site and filling each day's production

Mike Smith   Rhode Island : Design / Build / Repair / Restore

Mike Smith   Rhode Island : Design / Build / Repair / Restore

(post #96616, reply #5 of 5)

<spec a "grout " mix..>

Mike thanks for that tip, I never knew there was such

a thing, and I'm sure it would make things easier<G>!!!!

(post #96616, reply #4 of 5)

I would be a little more cautious before ordering my 'crete.

Some quick measurements on a typical block will tell you what fraction of the total block volume is air to be filled.  That one number of 60 percent, when applied against a foundation of dimensions 30' x 45' x 8' high, would tell you that the fill quantity is 18 cy against a total wall volume of 30 cy.

IMHO, the guys telling you to order the whole 30 against a net requirement of 18, must have convenient places to put the over ten cubic yards of leftover.  And sending it back in the truck is a very costly no-no.

My redimix supplier charges me almost $84/cy for delivery of the kind of mix you need.  The idea of paying an extra $840 plus 8% sales tax "just to be sure," sounds like "cost-plus economics" to me.  Ain't the way I do biz.


There are a lot of stocked building material items my suppliers will take back without restocking charges, and in the case of lumber, they will even pick it up.  Anything that is special order . . . fuhgeddaboudit.  I order carefully, making sure of my quantity, and add up as required.

Concrete the same.


Gene Davis, Davis Housewrights, Inc., Lake Placid, NY