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Safety Cue
Task-specific safety guidance for ordinary corner and intersection work.
Chapter 6
Build Block Wall Corners and Intersections
Build one stepped block corner and one T-intersection practice assembly, controlling course height, bond, plumb, rack-back, ties or anchors, and wall-line transfer to intersecting work.
Field Cue System
These cues appear at the point of work. They identify safety, code, manufacturer, and measurement issues before they become rework, structural risk, or moisture damage.
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Critical Safety Cue
Serious injury, structural failure, or major damage is possible.
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Field Safety Cue
Practical work-area safety: access, footing, lighting, and housekeeping.
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Code Alert
Local requirements vary. Verify permit, inspection, and jurisdictional rules.
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Manufacturer Cue
Follow product-specific instructions for units, mortar, ties, and reinforcement.
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Measurement Cue
Square, plumb, rack-back, and course-height guidance.
Job Overview
This chapter qualifies you to build a plumb, square, bonded concrete-masonry corner lead and a T-intersection practice assembly. The finished work product is one stepped corner lead and one intersecting-wall assembly, each built to the approved bond pattern, rack-back detail, course elevations, and tie or reinforcement schedule, and each inspected before mortar hardens.
Chapter 5 taught you to build a straight nonstructural block practice wall using bed joints, head joints, and a story pole. This chapter extends that skill to the point where two walls meet — a corner, where one wall turns a angle, and an intersection, where a second wall joins the first as a T. Corners and intersecting walls control the line and course elevation for every unit laid between them; a corner lead built out of square or out of level carries that error into every wall section that follows it.
Nothing in this chapter authorizes structural or load-bearing corner and intersection work beyond the approved practice-assembly detail supplied for this project. This is nonstructural practice work built to demonstrate bond, plumb, square, rack-back, and tie placement.
Skills You Will Demonstrate
- RM-031 — Lay block corners, setting the first-course corner unit to level, square, and elevation and building the lead one course at a time.
- RM-032 — Rack back courses, stepping each successive course of the lead in the approved pattern while maintaining bond and overlap.
- RM-033 — Tie intersecting walls, installing intersecting-wall ties, bond units, reinforcement, or anchors exactly as specified at the T-intersection.
- RM-034 — Maintain plumb, checking both wall faces and the corner arris at each course using the level.
- RM-035 — Maintain bond pattern, preserving the specified overlap and joint alignment through the corner and intersection.
- RM-036 — Inspect corner strength and alignment, verifying square, plumb, bond, rack-back, ties, and course height before continuing adjacent wall work.
Where This Skill Fits
Chapter 4 established the layout, corner references, and story pole for a masonry wall. Chapter 5 applied bed joints, head joints, and course control to a straight run. This chapter applies that same course control to the two conditions every real block wall eventually reaches: a turned corner and an intersecting wall. The lead you build here is what a mason's line is stretched from in every subsequent wall section, so its square, plumb, and elevation control the accuracy of everything built between leads.
Chapter 7 depends on the reinforcement and grouting skills you demonstrate placing ties and anchors at the intersection in this chapter. Chapter 9 repeats this corner-and-lead logic in brick. The Chapter 20 capstone assumes the learner can build and check a corner lead without supervision.
Scope and Intended Use
This chapter covers:
- laying out and squaring both wall baselines for a corner or T-intersection
- setting the first-course corner unit to level, square, and elevation
- building a stepped corner lead one course at a time with the approved rack-back pattern
- maintaining bond, overlap, and course height using the story pole through the lead
- checking plumb on both wall faces and the corner arris at each course
- installing intersecting-wall ties, bond units, reinforcement, or anchors exactly as specified at a T-intersection
- stretching mason's lines from the completed lead for adjoining wall work
- inspecting corner square, plumb, bond, rack-back, ties, and course height before mortar hardens
This chapter does not authorize the learner to:
- build a load-bearing corner, retaining-wall corner, foundation-wall corner, or any structural intersection without the exact engineered design and inspection sequence supplied by a qualified professional
- create an unapproved tooth or unsupported intersection not shown in the approved corner or intersection detail
- build the lead more than the permitted number of courses above adjacent wall work before that adjacent work is brought up to match
- place grout, vertical reinforcement, or embedded anchors beyond what the approved detail for this practice assembly specifies; structural reinforcement and grouting are covered in Chapter 7
Any corner or intersection that fails square, plumb, bond, or tie inspection during this chapter must be corrected before the mortar hardens, or removed and rebuilt.
Reference Conventions
Establish these references before laying the first corner unit, and use them consistently through the lead and intersection.
| Term | Definition |
|---|---|
| Lead | The corner or end section of a wall built up several courses ahead of the intervening wall, used to establish line and course elevation |
| Rack-back | The stepped pattern in which each successive course of a lead is set back from the course below it, following the approved bond |
| Corner arris | The vertical outside edge formed where the two wall faces meet at the corner |
| Intersecting-wall tie | A metal tie, bond unit, or anchor connecting an intersecting wall to the primary wall at a T-intersection, per the approved detail |
| Tooth | An unapproved, unsupported step or interlock at an intersection not shown in the approved detail; not permitted in this chapter |
Corner and Intersection Identification Record
Before beginning layout, record the assembly identity and controlling documents directly on the work order:
Assembly name: ______ Corner angle: ______ Intersection type: ______ (T-intersection / other, per approved detail)
Approved corner/intersection detail on hand: ______ (Y/N) Tie or anchor product specified: ____________ Wall thickness: ______ Height limit for this practice assembly: ______
Date built: ____________ Mason name: ____________
Prerequisites
- Completed Chapter 1 readiness plan for the selected corner/intersection practice project, with an Approved or Conditional-cleared decision
- Completed Chapter 2 work-area setup, including mixing area, scaffold if required, silica controls, and washout containment
- Completed Chapter 3 mortar mixed and staged to the specified type and workability
- Completed Chapter 4 layout for both wall baselines, including corner reference points, story pole, and mason's-line setup
- Approved corner and intersection detail specifying bond pattern, rack-back sequence, wall thickness, height limit, and tie or anchor schedule
- A level, dry, and inspected base for both wall directions
Common Field Fundamentals
A corner lead is built to establish two things that the rest of the wall depends on: the corner angle and the course elevation. Every unit laid in the intervening wall is checked against the line stretched from the lead, so an error in the lead is transferred into the entire wall run. An intersection adds a third requirement — a tie or anchor connection between two walls that must accommodate differential movement while transferring the specified load or restraint, exactly as the approved detail requires.
BaselinesBoth wall lines marked and verified square before laying begins
First-course corner unitSet to level, square, and elevation before the lead continues
Rack-backEach course stepped back per the approved bond pattern
PlumbBoth wall faces and the corner arris checked at each course
Ties or anchorsInstalled at the T-intersection exactly as specified
Story poleControls course elevation through the lead and intersection
Mason's lineStretched from the checked lead for adjoining wall work
Final inspectionSquare, plumb, bond, rack-back, ties, and course height verified before mortar hardens
Corner and Intersection Judgment
Do not create an unapproved tooth or unsupported intersection. If the approved detail does not show a specific tie, anchor, bond-unit, or rack-back arrangement for a condition encountered in the field, stop and obtain the missing detail rather than improvising an interlock. Do not build the lead more than the number of courses above adjacent wall work permitted by the approved detail; an overextended lead is unsupported and unstable.
RM-031 – RM-036
Layout / Construction / Inspection
Block Wall Corner and Intersection Assembly
A. Finished-Project Specification
Deliverable: one stepped concrete-masonry corner lead built to the approved corner detail, and one T-intersection built to the approved intersection detail, each with verified square, plumb on both faces and the corner arris, correct bond and rack-back, specified ties or anchors installed at the intersection, verified course elevations against the story pole, and a completed inspection record.
B. Component Schedule
| Component | Quantity | Material | Finished Size | Preparation |
|---|---|---|---|---|
| Corner-lead units | Per approved detail component count | Concrete masonry unit as specified | Per specified unit dimensions | Dry-laid and adjusted before mortar is spread |
| Intersection units | Per approved detail component count | Concrete masonry unit as specified | Per specified unit dimensions | Dry-laid and adjusted before mortar is spread |
| Intersecting-wall ties or bond units | Per approved tie schedule and spacing | Corrosion-resistant tie, bond unit, or anchor as specified | Per manufacturer instructions | Installed at the specified course and embedment |
| Joint reinforcement (if specified) | Per approved detail | As specified in the approved detail | Per specified width and length | Placed in the bed joint at the specified courses |
C. Fastener and Hardware Schedule
| Joint / Location | Fastener or Hardware | Spacing / Embedment | Installation Direction | Seating Condition |
|---|---|---|---|---|
| T-intersection tie course(s) | Intersecting-wall tie or bond unit as specified in the approved detail | Per the approved course spacing and manufacturer embedment depth | Per manufacturer instructions; do not reverse or invert the specified orientation | Fully embedded in the mortar joint with no exposed unbedded length |
Do not treat "tie" or "anchor" as a complete specification. Identify the exact product, spacing, and embedment from the approved detail and manufacturer instructions before installation.
D. Reference Conventions
- Reference baseline: the primary wall's marked baseline, established in Chapter 4 and verified before the corner lead begins.
- Corner arris: the outside vertical edge of the corner, checked for plumb at every course.
- Lead face: each of the two wall faces meeting at the corner, checked independently for plumb and alignment.
- Intersection face: the face of the intersecting wall where it meets the primary wall, aligned per the approved detail.
E. Acceptance Standards
| Check | Standard |
|---|---|
| Corner angle / square | Diagonal measurements match within the tolerance stated in the approved detail; if none is stated, record the measured deviation and correct before continuing rather than estimating a tolerance |
| Plumb | Both wall faces and the corner arris plumb within the tolerance stated in the approved detail, checked at every course |
| Bond and rack-back | Bond pattern and rack-back step match the approved detail at every course; no aligned vertical joints across courses unless the design permits them |
| Course elevation | Each course height matches the story pole mark for that course |
| Intersecting-wall ties | Installed at the specified course, spacing, and embedment, fully bedded in mortar, with no substitution of product or orientation |
| Lead height above adjacent work | Does not exceed the number of courses stated in the approved detail before adjacent wall work is brought up to match |
| Tooth or unsupported intersection | Not present; every intersection detail matches the approved drawing exactly |
F. Layout and Base Verification
- Review corner or intersection detail, bond pattern, reinforcement, anchors, wall thickness, and height. Confirm the detail is the current approved version and matches the assembly being built.
- Verify base dimensions and square. Measure both wall baselines and check the included angle with a framing square or diagonal measurement before laying any unit.
- Mark both wall baselines. Chalk-line both baselines from the Chapter 4 reference points.
- Dry-lay the first-course corner units. Position units without mortar to confirm module and joint width in both wall directions.
- Adjust layout for correct overlap and modular dimensions. Shift the dry-laid units as needed to minimize cuts while preserving the specified joint width.
G. Corner Lead Construction
- Spread mortar for the corner lead. Spread and furrow a bed sized for the first two or three units at the corner.
- Set the first corner block to level, square, and elevation. Tap the unit to the story-pole mark, check level in both directions, and verify square against the second baseline before continuing.
- Lay units extending in both wall directions. Butter and set units along each baseline from the corner unit.
- Check the corner angle with square or diagonal controls. Recheck the diagonal measurement before laying the second course.
- Build the lead one course at a time. Complete and check each course before beginning the next.
- Rack back each course using the approved stepped pattern. Step each successive course back from the one below per the approved bond and rack-back detail.
- Maintain bond and overlap. Confirm head-joint offset matches the specified bond pattern at every course.
- Use the story pole to control course elevation. Mark and verify each course against the story-pole reference.
- Check plumb on both faces and the corner arris. Use the 4-foot level on each wall face and along the corner arris at every course.
H. Intersection Construction and Tie Installation
- Install intersecting-wall ties, bond units, reinforcement, or anchors as specified. Place the specified tie or anchor at the exact course and spacing shown in the approved detail, following manufacturer embedment and orientation instructions.
- Do not create an unapproved tooth or unsupported intersection. Build only the interlock or tie condition shown in the approved detail; stop and obtain the missing detail if a field condition is not covered.
- Stretch mason's lines from the lead for connecting wall work. Set line blocks or pins at the completed lead and stretch the line to the corresponding point at the far end of the intervening wall.
- Keep the lead only the permitted number of courses above adjacent work. Confirm the course count above adjacent work against the approved detail before continuing the lead higher.
- Tool joints at the proper time. Tool exposed bed and head joints when the mortar is thumbprint-hard, matching the specified profile.
I. Inspection and Correction
- Inspect corner square, plumb, bond, rack-back, ties, and course height. Complete the Acceptance Standards checks for every course of the lead and the intersection.
- Correct drift before mortar hardens. Reset any unit that fails square, plumb, bond, or elevation checks while the mortar remains workable.
- Document the completed intersection. Record final measurements, tie locations, and inspection results on the work order.
Common Readiness Inspection
Inspect every corner and intersection assembly using the same checks regardless of the specific bond pattern specified.
- Square check: confirm the corner angle was verified before the second course and rechecked at intervals through the lead.
- Plumb check: confirm both wall faces and the corner arris were checked with the level at every course, not only at the top of the completed lead.
- Bond and rack-back check: confirm the bond pattern and rack-back step match the approved detail at every course, with no unapproved aligned vertical joints.
- Tie check: confirm every intersecting-wall tie, bond unit, or anchor is installed at the specified course, spacing, and embedment, with no substituted product.
- Course-height check: confirm every course matches the story-pole mark for that course.
- Lead-height check: confirm the lead does not exceed the permitted number of courses above adjacent wall work.
Complete the Corner and Intersection Inspection Record below before stretching a mason's line to intervening wall sections.
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Failure Points and Troubleshooting
Cleanup
This chapter ends with an inspected, cured corner lead and intersection, not an assembly left to cure unchecked.
- Remove excess mortar from both wall faces and the corner arris without smearing
- Confirm every tooled joint is clean and free of loose mortar crumbs
- Protect the completed lead and intersection from rain, freezing, and impact during cure
- Store mason's line, line blocks, level, and story pole for the next work session
- File the completed inspection record with the Chapter 4 layout documentation for this project
Field Terms
- Lead
- The corner or end section of a wall built ahead of the intervening wall to establish line and course elevation.
- Rack-Back
- The stepped pattern in which each successive course of a lead is set back from the course below it.
- Corner Arris
- The vertical outside edge formed where two wall faces meet at a corner.
- Tooth
- An unapproved, unsupported step or interlock at an intersection not shown in the approved detail.
- Intersecting-Wall Tie
- A metal tie, bond unit, or anchor connecting an intersecting wall to a primary wall at a T-intersection.
- Diagonal Check
- A measurement of the diagonal distance across a laid-out rectangle or corner, used to verify square.
- Story Pole
- A reference pole marked with course heights, used to control elevation through a lead or wall section.
- Mason's Line
- A taut line stretched between leads or reference points to guide the alignment of intervening courses.
Skill Check
- Why must the corner angle be checked with a diagonal measurement before the second course is laid, rather than after the lead is several courses high?
- What is a rack-back, and why must each course be stepped back according to the approved detail rather than estimated by eye?
- Why must plumb be checked on both wall faces and the corner arris at every course, not only at the top of the completed lead?
- What must the mason do when a field condition at an intersection is not covered by the approved detail?
- Why must an intersecting-wall tie's product, course, spacing, and embedment be verified against both the approved detail and manufacturer instructions?
- Why is a corner lead built more than the permitted number of courses above adjacent wall work considered a safety and stability concern?
- What must be true of a corner lead before a mason's line is stretched from it to guide intervening wall work?
- Why must drift in square, plumb, or bond be corrected before mortar hardens rather than at the end of the lead?
- What is the difference between an approved intersection detail and an unapproved tooth, and why is the second one prohibited?
- Why does the story pole remain the controlling reference for course elevation through a corner and intersection, rather than measuring each course independently from the base?
Competency Rubric
| Competency | Independent Pass Standard | Not Demonstrated | With Assistance | Independently |
|---|---|---|---|---|
| RM-031 | Sets the first-course corner unit to level, square, and elevation and builds the lead one course at a time | |||
| RM-032 | Racks back each successive course of the lead in the approved stepped pattern while maintaining bond and overlap | |||
| RM-033 | Installs intersecting-wall ties, bond units, reinforcement, or anchors exactly as specified at the correct course, spacing, and embedment | |||
| RM-034 | Checks and maintains plumb on both wall faces and the corner arris at every course | |||
| RM-035 | Maintains the specified bond pattern and overlap through the corner and intersection | |||
| RM-036 | Inspects corner square, plumb, bond, rack-back, ties, and course height and corrects drift before mortar hardens |
Mark one column per competency. Only Demonstrated Independently awards the competency; Demonstrated with Assistance authorizes additional supervised practice but does not complete the requirement.
Corner and Intersection Inspection Record
| Item | Finding | Deficient | Correction | Reinspected (Date) |
|---|---|---|---|---|
| Corner angle / square | ||||
| Plumb — face 1 | ||||
| Plumb — face 2 | ||||
| Plumb — corner arris | ||||
| Bond and rack-back | ||||
| Intersecting-wall ties | ||||
| Course elevation | ||||
| Lead height above adjacent work |
Final result: ______ (Pass / Corrected and Repassed / Rebuild Required) Date: ____________ Mason name: ____________
Performance Check
With the corner lead and intersection complete, review the Corner and Intersection Inspection Record against the Acceptance Standards table and confirm every course has a recorded square, plumb, bond, and elevation result. Confirm every installed intersecting-wall tie matches the approved product, course, spacing, and embedment. Correct any recorded deficiency while the mortar remains workable, or remove and rebuild the affected courses. Do not stretch a mason's line from the lead to guide intervening wall work until the final result is recorded as Pass or Corrected and Repassed.
Project Closeout
You have completed the sixth chapter in the residential masonry sequence: building block wall corners and intersections. This chapter required you to lay block corners (RM-031), rack back courses (RM-032), tie intersecting walls (RM-033), maintain plumb (RM-034), maintain bond pattern (RM-035), and inspect corner strength and alignment (RM-036).
You now have a plumb, square, bonded corner lead and a correctly tied T-intersection, each verified against the approved detail and documented on the inspection record. This lead is the reference every intervening wall course depends on, and the tie installation practiced here carries directly into Chapter 7, where you place reinforcement and grout in a concrete-masonry wall section.
File your completed Corner and Intersection Inspection Record with the Chapter 4 layout documentation for this project. You will reference this exact lead and intersection throughout the remaining block-masonry chapters.