Building Up: Story Pole, Coursing, and Multi-Course Walls

Why Multi-Course Walls Demand Precision from the Start

A single crooked course multiplies into a leaning, out-of-plumb wall by the time you reach course eight. Masonry has no rewind button—mortar sets, blocks are heavy, and tearing out work costs time and material. The story pole, the level, and the mason's line are the tools that keep every course honest before the next one goes on.

The Story Pole: Your Vertical Ruler

A story pole is a straight length of wood—typically a 1×2 or 1×3 furring strip—marked with the exact height of every course in a wall. For standard 8-inch CMU construction, each course height equals the unit height plus the mortar joint:

• Unit height: 7-5/8 inch
• Mortar joint: 3/8 inch
• Total per course: 8 inches exactly

You mark the pole starting at the bottom (course 1 top = 8 inches, course 2 top = 16 inches, and so on up to course 8 = 64 inches). Mark each line clearly with a pencil and label it: C1, C2 … C8. A correctly graduated story pole lets you confirm in seconds whether your wall is gaining or losing height, and by exactly how much. Hold it plumb against the corner lead after each course and read the gap or overlap against your mark. Record both the target and actual measurements in your lab log at courses 2, 4, 6, and 8.

Building Corner Leads

Corner leads are the stepped pyramid shapes you build at each end of the wall first. They act as guides for every course of block that fills between them. A lead typically steps back one block per course so that it rises like stairs. Leads must be:

• Plumb on both exposed faces
• Level from front to back across the block
• On-course height-wise, matching the story-pole marks

Check plumb with a 4-foot level held against the face of the blocks, not the mortar. Apply light, even pressure; do not force the level. Check both faces of every course before you set the next. If a block is out, tap it with the trowel handle while the mortar is still workable. Once the mortar begins to stiffen, the block position is fixed.

Pulling the Line and Filling the Wall

Once both leads are built, you pull a mason's line between them using line blocks hooked to the top outside edge of each lead block. The line sits flush with the top outside face of the course you are laying—this is your height and alignment guide for every block in the fill courses.

Lay blocks so their top outside edge just touches the line without pushing it. A line pushed outward will throw every block in the course off alignment. Keep the line taut; a sagging line produces a bowed wall.

Closure Block Technique

The last block set to complete any course is the closure block. It fills a gap from both sides, so you cannot slide it in from one end. Proper closure technique:

1. Butter both head joints of the opening (both block faces already in the wall).

2. Butter both ends of the closure block itself.

3. Lower the block straight down into the opening without dragging it sideways, which would wipe the butter off.

4. Check that all four buttered faces have full mortar contact with no voids.

Tooling Joints

Tool joints when the mortar reaches thumbprint hardness—when you press your thumb into the joint and it leaves a clean print without mortar sticking to your thumb or crumbling out. Too early and the joint smears; too late and tooling cracks the mortar. Use a 5/8-inch convex jointing tool (also called a sled runner for long bed joints) to produce a concave profile. This profile sheds water and compresses the mortar surface for better durability. Tool all bed joints first, then head joints.

Running Bond Pattern

In running bond each course offsets by half a block from the course below—typically a 4-inch offset for 8-inch CMU. This overlap transfers load across head joints and is the most common CMU bond pattern. Use half blocks at corners and at the ends of alternate courses to maintain the pattern.

Safety in the Lab

• Eye protection (safety glasses or goggles): required at all times around cutting, mixing, and laying operations. Mortar and block chips are unpredictable.
• Gloves: mortar is caustic (high pH) and prolonged skin contact causes burns. Wear chemical-resistant gloves or wash hands frequently.
• Back safety: CMU blocks are heavy—standard 8-inch stretchers can weigh 28–35 lb. Use a straight back and leg lift; get help or use a block cart for large quantities.
• Foot protection: steel-toed boots protect against dropped blocks.
• Housekeeping: keep the work area clear of mortar droppings and block scraps to prevent trips and falls.
• Mixer safety: keep hands and tools away from the mixer drum when it is running. Follow the manufacturer's lockout procedure before clearing a jam.

Plumb Tolerance

The standard tolerance for a plumb CMU wall in most specifications is 1/8 inch per 4 feet of height. Check plumb at both the inside face and the outside face of the wall—a block can be plumb on one face and tilted on the other if it is not uniform in thickness. Record any deviation and correct it before laying the next course.