Flemish Bond

Part of Brick Making

Alternating headers and stretchers for strong, attractive walls.

Why This Matters

When you lay bricks, the pattern in which you arrange them determines both the strength and appearance of the wall. A random stack of bricks with aligned vertical joints will crack and separate under even moderate loads. A well-chosen bond pattern distributes weight evenly, ties the wall together across its full thickness, and resists lateral forces from wind, earth pressure, and seismic movement.

Flemish bond is one of the strongest and most economical patterns for solid walls. By alternating headers (bricks laid end-on, spanning the wall’s thickness) and stretchers (bricks laid lengthwise along the wall face) in every course, you create an interlocking structure where no vertical joint aligns with the one above or below it. Every header acts as a tie, binding the front face to the back face of the wall.

Beyond strength, Flemish bond produces a visually distinctive pattern that has been used for centuries in buildings meant to last. In a rebuilding context, this matters because structures built with proper bonding patterns require less material, less mortar, and less maintenance than poorly bonded walls — and they survive earthquakes, storms, and settling far better.

Brick Terminology and Dimensions

Before laying Flemish bond, you need to understand the basic brick vocabulary:

• Stretcher — A brick laid flat with its long face showing on the wall surface. Length runs parallel to the wall.
• Header — A brick laid flat with its short end showing on the wall surface. Length runs perpendicular to the wall, tying front and back faces together.
• Queen closer — A brick cut in half lengthwise. Used at corners to maintain the bond pattern offset.
• Bat — A brick cut to a shorter length. A “three-quarter bat” is 75% of a full brick.
• Course — A single horizontal row of bricks.
• Bed joint — The horizontal mortar joint between courses.
• Perpend — The vertical mortar joint between bricks in the same course.

For Flemish bond to work correctly, the brick width must be exactly half the brick length minus one mortar joint. Standard proportions are approximately 2:1 in length to width. If your bricks are 220mm long and 105mm wide with 10mm joints, a header (105mm) plus a perpend (10mm) equals half a stretcher-plus-perpend (115mm). This dimensional relationship is what makes the offset pattern possible.

Check Your Mold Dimensions

Before making thousands of bricks, lay out a test pattern dry (without mortar). Place a stretcher next to a header with a finger-width gap for mortar. If the header-plus-gap does not equal exactly half the stretcher-plus-gap, adjust your mold dimensions. Getting this wrong makes Flemish bond impossible.

The Flemish Bond Pattern

Basic Layout

In Flemish bond, every course follows the same rule: alternate one header and one stretcher across the entire length of the wall. The key is that each course is offset by half a brick from the one below, so that every header sits centered on the stretcher below it, and vice versa.

Course 1: Stretcher — Header — Stretcher — Header — Stretcher… Course 2: Header — Stretcher — Header — Stretcher — Header… Course 3: Same as Course 1 Course 4: Same as Course 2

When viewed from the front, this creates a distinctive checkerboard-like pattern where headers and stretchers alternate both horizontally and vertically.

Starting a Corner

Corners are where Flemish bond gets tricky. To maintain the alternating pattern around a 90-degree corner:

1. Start Course 1 with a header at the corner on one face and a stretcher on the adjacent face
2. Immediately after the corner header, place a queen closer (half-width brick cut lengthwise) — this creates the half-brick offset needed
3. Continue with the normal header-stretcher alternation along both faces
4. On Course 2, reverse: start with a stretcher at the corner on the first face, header on the adjacent face
5. Again place a queen closer after the corner piece

The queen closer is essential. Without it, the vertical joints in consecutive courses would align, creating a continuous crack line — the very thing bond patterns exist to prevent.

Step-by-Step Corner Sequence

1. Lay a header brick at the exact corner, faces flush with both wall planes
2. On the return face, butt a stretcher against the header’s side
3. Place a queen closer tight against the header on the main face
4. Continue alternating header-stretcher along the main face
5. Continue alternating stretcher-header along the return face
6. Next course: swap the starting brick — stretcher at corner on the main face, header on the return
7. Place queen closer on the return face this time
8. Continue the alternation

Laying Flemish Bond Step by Step

Preparation

1. Set up string lines along the wall face at the height of each course. Use a spirit level or water level to ensure the line is perfectly horizontal.
2. Mix mortar to a workable consistency — it should hold its shape when squeezed but spread easily under the brick’s weight.
3. Lay out a dry course first to check spacing and identify where cuts are needed.

Laying Each Brick

1. Spread the bed. Trowel mortar onto the top of the previous course (or foundation), about 12-15mm thick and slightly wider than the brick. Furrow the center with the trowel tip to help the brick settle evenly.

2. Butter the end. Apply mortar to the end of the brick that will form the perpend joint. For headers, butter one short end. For stretchers, butter one short end.

3. Place and press. Set the brick on the mortar bed and press it down firmly until it sits at the string line height. Push it sideways against the previously laid brick to compress the perpend joint.

4. Check alignment. Use a straightedge along the wall face to ensure the brick is flush. Check with a level that it is not tilting forward or backward.

5. Strike the joint. Once the mortar is “thumbprint firm” (holds an impression but does not stick to your thumb), tool the joint to compress and smooth it. This seals the surface against water penetration.

6. Repeat the alternation. If you just laid a stretcher, the next brick is a header. If you just laid a header, the next is a stretcher.

Maintaining Level and Plumb

Every 3-4 courses, check:

• Level — Place a level across the top of the course. Adjust by tapping high bricks down with the trowel handle.
• Plumb — Hold a plumb bob or level against the wall face. The face must be perfectly vertical.
• Gauge — Measure from the foundation to the top of the current course. Each course (brick plus mortar joint) should be a consistent height. Use a gauge rod — a straight stick marked at course intervals — to check quickly.

Flemish Bond vs. Other Common Bonds

Feature	Flemish Bond	English Bond	Stretcher Bond
Pattern	Alternating H-S every course	Alternating full header and full stretcher courses	All stretchers (half-brick thick wall)
Wall thickness	One brick (full header depth)	One brick (full header depth)	Half brick only
Strength	Excellent — ties on every course	Very strong — full header courses	Weak — no cross-ties
Brick economy	Good — fewer headers than English bond	Uses more headers	Best economy but thin wall
Appearance	Decorative checkerboard pattern	Plainer, regular bands	Simple, modern look
Difficulty	Moderate — queen closers needed	Easier — no mixing in courses	Easiest
Best use	Load-bearing walls, visible facades	Foundations, retaining walls	Partition walls, veneers

Common Mistakes and How to Avoid Them

Aligned perpends. The most serious error. If vertical joints line up across two or more courses, the wall has a structural weakness. After every course, step back and sight down the wall — perpends should stagger in a clear zigzag pattern.

Forgetting the queen closer. At corners, it is tempting to skip the queen closer and just shift bricks. This inevitably throws off the pattern within a few courses. Always cut and place closers at every corner, every course.

Inconsistent mortar joints. Thick joints at one end and thin joints at the other cause the wall to lean or curve. Use a gauge rod and string line religiously. If joints are drifting, stop and correct before continuing.

Headers not spanning full wall thickness. A header must run completely through the wall, with its face flush on both the front and back. If headers are short of the back face, they provide no structural tie. Check by sighting along the back face periodically.

Mortar too wet or too dry. Soupy mortar squishes out under the brick’s weight and creates weak joints. Stiff mortar will not bond to the brick surface. The mortar should hold a trowel-cut cleanly without slumping.

Variations of Flemish Bond

Monk Bond (Flying Flemish)

Each course has two stretchers followed by one header, repeating. Easier to lay than true Flemish, uses fewer headers, but slightly weaker because ties are less frequent.

Sussex Bond

Three stretchers to one header in each course. Even more economical with headers but provides less cross-tying. Suitable for less critical walls.

Double Flemish Bond

True Flemish bond on both the front and back faces of the wall. This is the standard described above and provides the strongest interlocking.

Single Flemish Bond

Flemish pattern on the front face only, with the back face laid in a simpler pattern (usually English bond). Used when only one face needs to look decorative. Slightly weaker than double Flemish.

Structural Considerations

Load-Bearing Capacity

A one-brick-thick wall in Flemish bond (approximately 230mm or 9 inches including mortar) can support:

• Single-story buildings with timber roof — comfortably
• Two-story buildings — with adequate foundation and careful construction
• Three or more stories — requires thickening at lower levels (1.5 or 2 brick thickness)

For walls thicker than one brick, Flemish bond is applied to each face, with the interior filled with headers or rubble. The key principle remains: every course must include cross-ties that bind the full wall thickness.

Openings

Around windows and doors, the bond pattern is interrupted. Use soldier courses (bricks stood on end) or arches as lintels above openings. At the jambs (sides of openings), maintain the bond pattern right up to the opening, using cut bricks as needed to keep the alternation correct.

Weather Resistance

Flemish bond’s frequent perpend joints create more potential water entry points than stretcher bond. In wet climates, ensure all joints are well-tooled (concave or weathered profile) and consider applying a lime wash to the exterior face to seal the surface.