Building a block wall can be a major undertaking, whether it is a retaining wall, a freestanding wall, or part of a larger structure. Before embarking on the build you'll need to know the project cost. Estimating the cost is mostly a matter of estimating your total material needs. Once you have those down, you can determine the cost of those materials based on the prices in your area.
Things You'll Need
 Local building codes
 Materials list
 Block and mortar estimate table
 Calculator
 Measuring tape

Determine the type of blocks required for the specific job. Consult with the retailer where you'll be buying the blocks for recommendations on block type and size. Many walls use standard 8inch blocks for building.

Calculate the square footage of the block wall to determine number of blocks and amount of mortar needed. Multiply the wall length by its height, both in feet, to determine the square footage of the wall.

Determine the concrete footing size needed for your wall. All footings should reach below the frost line for your area. Check with the local building inspector for footing size needed in your area to meet the building codes. Determine the total volume of concrete needed for the footer by multiplying the depth of the footer by the width and then multiplying that number by the length to determine the volume in cubic feet.

Consult a block and mortar estimate table to determine the number of blocks of your chosen type that you need to build a wall of a particular size. You can find block and mortar estimate tables at most home improvement and hardware stores, or online at their retail websites. Typically, the estimates are for every 100 square feet of wall surface, so divide your wall size by 100 to determine the number of 100 square foot units needed. Find the block type on the table and locate the number of blocks per 100 square feet. Multiply this block number by the number of 100 square foot units in your wall and you'll have the estimate of the total number of blocks necessary to build your wall type. Use the same process to find the amount of mortar needed in cubic feet.

Price the material costs for your wall of block, mortar and concrete. Multiply the cost of each block by the total number needed for your wall to determine the total block costs. Divide the total mortar amount needed by the amount of mortar provided per bag of the mortar type you're using for your wall to determine the total number of bags required. Multiply the number of bags required by the per bag cost to determine the total cost of the mortar needed. Use the same process used to calculate mortar needs to determine concrete needs. If building codes determined the need for rebar in the footings, or height of the walls demand the use of reinforcing rods within the blocks then multiply the length of bars or rods needed by the cost per foot.

Add all of the separate material costs to determine the total material cost necessary for building your block wall. If hiring labor to aid in the wall construction, consult with the personnel involved to estimate their block laying speeds, divide the total number of blocks by the number they estimate laying per hour, to determine total hours of labor necessary. Multiply this by their rate per hour for total estimated labor costs and add to the total material costs to get the estimated costs including labor of building your block wall.
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