What Is Better: Poured Walls or Block Walls?

Solid vs. Mortar

• Both solid concrete and concrete block walls are set on solid footings of poured concrete. Solid walls are formed by building or erecting wood or metal forms, containers which will confine the concrete into the wall space until it hardens or cures into a single solid piece. Block walls are assembled by attaching rows of individual blocks with holes in them with mortar. A solid wall is built in one continuous action; block walls are built in many steps and require skilled masons for installation.

Blocks Have Weak Points

• All concrete has great compressive strength, the ability to withstand heavy pressure, like weight, directly on it. No concrete, solid or block, has great tensile strength, the ability to endure bending or twisting. Variations in force can exert these tensile pressures and cause cracking on either solid or block walls; but block walls have hundreds of built-in weak spots in the mortar joints, while a solid wall may be able to tolerate more slight flexing with only minor surface cracks.

Reinforcing Adds Strength

• Concrete block walls can be strengthened with the addition of reinforcing bars vertically in the holes in the blocks. A technique called dry-stacking does not use mortar, but binds blocks together with a surface bonding cement and reinforcing bars in gaps which then are filled with concrete. The result is a wall almost as solid as a poured concrete wall. Solid walls are poured with reinforcing bars set in the forms.

Blocks Offer Remote Alternative

• Blocks have one big advantage over poured concrete -- a block wall can be assembled in areas too remote to be serviced by a concrete mixer truck. Mixer trucks are filled at "batch" plants, which must be within 90 minutes of a job site. Some rural areas and other sites may be too distant to be serviced adequately by mixer trucks, so blocks are a good alternative.

Rock Makes a Difference

• A major difference between solid concrete and concrete block is the type of gravel or aggregate used. Poured concrete may have gravel up to 3/4-inch in diameter; blocks are usually made with gravel no more than 1/4-inch. That matters because the stones are what gives concrete much of its strength -- the cement is just a paste to hold the stones in place (sand is simply smaller stone to fill gaps). Larger stones may bear more pressure, especially when bonded tightly together. Blocks are made with hollow cores to reduce weight,