not a lot. but assuming 9"x3" and using this brick calculator it works out at 0.0003 cubic meters of mortar or 0.91kg of sand and 0.25kg of cement per brick.
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For every block, you will use approximately 1.2 pounds of mortar
.48 per brick
a brick costs about $1.50 per brick so a wall of 5 bricks would be $7.50.
That depends on where you are building the house, the size of the house and the type of bricks used. The larger the house, the more labor and materials it requires. Also, the type of bricks used vary in costs, so it would depend on what kind you choose.
one cubic meter is equivalent to 1000 cubic decimeters or 1000 liters. assuming the amount of mortar used has a volume of 2/3 of 1 brick (figuring on standard red brick of 2.5 x 5 x 10 inch bricks) per brick, then the amount of mortar used will be about 333 1/3 liters. if 1/3 of the volume of the mortar is water then the dry ingredients are equal to 222.222 liters. of that: 1/6 of the dry ingredients are portland cement if you are using a 3:2:1 (sand, lime, cement) or 37.04 liters.
65 BLOCKS PER 74 POUND OF MORTAR (THAT YOU ADD SAND TO) 80 POUND PREMIX MORTAR JUST ADD WATER 27 BLOCK 8X8X16
An average north American housebrick weighs about 5 1/2 pounds. - Asking things such as "per square foot" depend on unstated factors like -which way are they laying, and with mortar or not.
Brick retaining walls are usually 2 walls with a brick row on top. Since you did not include the size of your brick take the size of your wall 25 x 3 = 75 x 2 (the back wall) = 150 sq feel x (how many of your brick per sq foot) + 100 bricks for top row = total brick x 10% waste factor 3.54 bricks per foot would be - 150 x 3.54 = 531 + 100 = 631 + 63 = 694 Note - you may have to fill the void with mortar or concrete if this is to be a "retaining wall" holding back fill dirt or the wall will crack. You also will have to backfill with gravel and provide drainage thru the wall. Study up, you don't want to do this twice.
On a per-foot basis, it would be the thickness of the wall in feet multiplied by the height in feet multiplied by the combined density of the brick and mortar. My AISC manual has 120 lbs per cubic foot for a normal brick wall, so a typical single wythe wall (4" thick) would weigh 40 lbs square foot of face area.
are these concrete blocks and allowing for mortar. 12.5 per square metre, 62.5 per cubic metre with mortar