To interlock or not to interlock
by Dan Powell
I take issue with three of the alleged advantages of the interlocking block system which are the following:
Earthquake resistance and
Ease of construction because they are self aligning.
Ability to produce thinner walls
There are some big liabilities that go with the interlocking system that I can see. First is the dependence on cement to make them strong enough to not break the overlapping flange in the event of lateral wall movement, but the cement and shape also makes them subject to shattering under the same circumstances. With the loss of flexibility and the shattering induced there is also introduced the potential for catastrophic failure where a section of block blow out causing a wall collapse. Obviously this hasn’t yet been proven but with the increase of earth block construction worldwide we will soon see the actual performance characteristics empirically. The vertical compaction also introduces problems with the need for mortar increasing cost as well as failure potential due to differential materials fatigue. I assume that the block are vertically pressed which would be the only way to make an interlocking block, (see my explanation at www.adobemachine.com/vervshor.htm )
Another liability to interlocking block is the difficulty in making corners, intersections, buttresses, and arches. Not to mention domes and vaults which are very important to earthquake resistant architecture as well as aesthetics.
questionable advantage to interlocking block is the ability to construct thinner,
steel reinforced earth block walls. Although this would appear to be an
advantage you would be in the same league as either a fired brick or concrete
masonry unit. The embodied energy, energy inefficiency and CO2 emissions in any
cement or steel intensive product is too high to justify a thinner wall for any
My dad, W.C Powell, designed an interlocking block press for Reickerman