Here's simpler, quicker way to erect concrete-block walls
Greenwood, Maine — During many years of varying work experiences, Fred Kennedy used just about every hand tool devised by man with one exception - the mason's trowel. That omission became significant only when he made plans to build his own home here in this rural Maine community. If he were to build the cellar walls of cement block, he would have to acquire some basic bricklaying skills in a hurry. Then someone suggested he look into surface bonding. He did. What he found is a much simpler and much faster way to go for the would-be builder with little or no experience in laying bricks or concrete blocks.
Surface bonding, according to the University of Georgia College of Agriculture (which began developing the concept in 1967), is ''both a material and a technique'' for erecting concrete-block walls without the use of mortar. In other words, no mortar is used to hold the blocks together. They are stacked dry, much the way a child stacks toy building blocks. After the wall is up, the bonding is done by troweling a layer of the bonding compound - a cement and fiber-glass mix - over both sides of the wall.
The compound dries to form a skin of remarkable strength which holds the blocks together more effectively than conventional mortar.
The surface-bonded wall, in fact, can resist lateral pressure several times more effectively than a mortar-laid wall. On the other hand, it is not so effective at withstanding vertical pressure. This is why current recomendations from the National Concrete Masonry Association limit the height of a surface-bonded building to two stories. Commercial buildings have been constructed as high as 14 feet in this manner.
Another advantage of surface bonding: It makes the wall highly waterproof.
On long walls, it is recommended that concrete pilasters (a double thickness of the blocks) be built in at intervals roughly 18 times the width of the wall. These pilasters are tied into the wall by laying alternate courses crosswise. Reinforcing rods are placed through the hollow cores of the outer thickness, which are then filled with concrete.
A skilled mason's productivity has been found to increase 70 percent when using the surface-bonding approach to building. But for the average home handyman, the simplicity of the method, more than its speed, is the important factor.
Many do-it-yourselfers who would not tackle conventional block-wall construction have the confidence to go the surface-bonding route. As Fred Kennedy put it: ''Who cannot stack one block on top of another?''
In surface-bonding, the first course of blocks is often laid in a bed of mortar. This is done simply to start with a level first course on the usually irregular poured-concrete base. After that, the walls go up in rapid order as the blocks are stacked dry. Because of some irregularities in the blocks, it may be necessary periodically to insert shims (or even a little mortar) under the blocks to keep them level. The surface-bonding compound goes on when the wall is complete.
Encouraged by the Kennedy experience, I recently erected two 20-foot-long walls on poured footings. The blocks were stacked one day and, with my son-in-law to help, the surface bonding was applied, using a mason's trowel, on another. It was as simple as that! We did find that the compound went on more smoothly when applied in a very wet, sloppy state.
Because of the fiber glass in the mix, a perfectly smooth finish is almost impossible to achieve. Where this is important, a conventional stucco or plaster finish can be applied over the surface bonding.
For more detailed information, send $1 to the United States Government Printing Office, Washington, D.C. 20402 and ask for: ''Construction With Surface Bonding,'' Bulletin No. 374.