The masonry trade is like no other.

It seems that "masonry bond" and "masonry dimensions" are two of the hardest terms for people in the design stage of our business to understand. Modular masonry is designed to work in 8-inch increments with a joint, which is why a typical block is 7 5/8 inches x 7 5/8 inches x 15 5/8 inches.

This basic information is seemingly something that is not well known in the design stage of our industry. When the contractor gets a set of plans that have dimensions of 4-feet 2-inches for pilasters and columns, he knows the designer has not done his homework.

When understood, this concept is one of the simplest in the masonry trade. There are two questions to consider. Do 1 add a joint to the dimension or take it away? When should it be one or the other? There are typically only three situations encompassing these two questions.

The first situation is coming from an inside angle to an outside right-angle corner. This scenario is the only situation that works exactly to even inches (two and one half 16-inch units are exactly 3-feet 4 inches-long). The calculation is tree because you have exactly the same number of joints as you have units.

The rule also is true in determining coursings because there is always the same number of joints as units. For example, three courses high is exactly 2-feet high because there are three units and three mortar joints, which is another reason why measurements are always taken at the top of the unit in coursing. The bed joint and one head joint are always thought of as one with the masonry unit and they cannot be separated from the unit.

The second situation is coming from an outside coiner to an opposite outside right-angle corner, as in a column. The measurement is 3/8-inch shorter than even inches because there is one less joint than units.

The third case is coming from an inside angle and going to an opposite inside angle. You must add 3/8 inch to the dimension because there is one more joint than units.

That said, notice that all 8-inch x 8-inch x 16-inch CMUs work to just three dimensions: even feet, even feet 8 inches, and odd foot 4 inches. These principles work throughout the masonry trade, with no exceptions.

If the dimension is shorter than typical by less than 1/2 of the bond dimension, or 1/4 of the entire unit if using half bond, the unit can be cut to dimension. Cutting achieves a desired bond for eye appeal and the only loss is the cost of the work and the waste left over from the action. Figure in the loss of the entire unit for pricing, as well as the sawing of the unit. This approach is not always the best, but possible.

However, if the dimension is longer than typical by no more than 1/2 of the bond dimension, or no more than 1/4 of the entire unit, there is a problem. For example: 1 foot 4 5/8 inches from an outside corner to an outside corner does not work at all because you can't make a unit longer. This dimension should be 1 toot 3 5/8 inches.

Actually, you can make anything work with a lot of cuts, but the final appearance is not good. Plus, it costs twice the money because of the wasted material and labor with the extra cuts. Situations like this is why the price of masonry can be so high and look so bad.

The statement, "The bed joint and one head joint are always thought of as one with the masonry unit and they cannot be separated from the unit" comes into play again when there is a change in mortar color, such as a recessed panel from the rest of the wall. The situation occurs when the top bed joint of the panel is to be a different color from the course of brick above it.

Architects often can't understand why there is an extra cost involved. Again, a brick is laid with mortar of the same color and type in the bed joint and one head joint. That cannot be changed.

In order to achieve a different type or color of mortar in one joint or the other of the same unit, you have to lay it with the same mortar and rake out the joint that is intended to be different. After the wall is cleaned, go back and point up the raked joint with the different desired color. The wall must then be cleaned again. This plan is the only way to achieve the desired result.

Hypothetically, if an architect wanted all the bed joints one color and all the head joints another in a project, the cost would be enormous. Unfortunately, similar requests are asked of masons everyday by thoughtless designers.

The masonry trade is like no other. The recognition of a few simple rules would make it a lot easier for everyone.

Ron Willis comes from a family of bricklayers and masonry contractors, working as an estimator/project manager and vice president. His software program for estimating and management--"The Masonry Estimating Wiz"--is a series of Excel spreadsheet-templates tied together into one workbook designed to work as a unit. Willis owns Masonry Estimating and Consulting Sere, ices. He can be reached at www.meacs.com.