Brick Veneer Crack Monitor Installation

Why this matters

A diagonal crack in brick veneer above a door or window is the most common diagnostic symptom a foundation contractor sees. The homeowner asks: is this getting worse? The contractor needs to answer with data, not gut feel, because the answer drives whether the next call is a structural assessment, a remediation quote, or a "the crack is stable, no action needed" closeout. The crack monitor (also called telltale, crack gauge, or movement monitor) is the cheapest, most defensible tool for that answer. Installed correctly, it measures crack movement to 1 mm precision over months. Installed wrong, it gives misleading readings and the contractor ends up either over-quoting unnecessary work or under-quoting a problem that goes catastrophic. The technique is simple; the discipline is in the protocol.

What a crack monitor measures

A crack monitor is a two-piece device, one piece anchored on each side of a crack. The two pieces overlap with a precision grid; as the crack opens, closes, or shears, the grid shifts and the new alignment reads directly in millimeters.

Three monitor types are common:

Avongard Standard Telltale: cross-grid plastic monitor, measures horizontal and vertical movement in 1 mm increments. The most-used model in residential structural monitoring. Range: 20 mm in each direction.

Avongard Corner Telltale: same principle, configured to monitor at 90-degree corners (interior or exterior).

Digital crack monitor (Geokon, Roctest): electronic readout, logging capability, sub-millimeter resolution. Used in commercial or litigation-grade monitoring.

For typical residential brick veneer diagnostics, the Avongard Standard telltale is the right tool. Cheap, simple, glassy-clear plastic that survives weather, easy to photograph.

When to install a monitor

Install monitors when:

Crack cause is uncertain. New crack discovered; could be active movement or aged settling.

Crack is in a location where movement matters. Above a door/window opening, at a corner of the building, at a foundation-to-veneer interface.

The homeowner is considering remediation but wants to see if the crack is stable before spending money.

Litigation or insurance documentation is needed. The monitor with date-stamped photos becomes evidence.

Time-budget for monitoring exists. Useful readings require minimum 3 months of observation; ideally a full year covering all seasons (wet, dry, freeze, thaw).

Do NOT install a monitor when:

Crack is obviously catastrophic (greater than 1/4 inch wide, mortar joint failure, visible structural displacement). Skip to engineering assessment; the monitor is not adding decision value.

Active leaking through the crack is visible (water staining, salt deposits, vegetation growing in the crack). The water itself is the diagnostic.

Homeowner wants immediate action. Monitoring takes months. If the homeowner needs an answer in two weeks, hire an engineer for a single-visit assessment instead.

Choosing monitor locations

Walk the building exterior and interior. Identify cracks by:

Direction: vertical, diagonal, stair-step through mortar joints, horizontal.

Width: hairline (under 1/32 inch), thin (1/32 to 1/8 inch), wide (over 1/8 inch).

Location: above/below openings, at corners, at the foundation line.

Pattern: single crack vs systematic pattern (multiple parallel cracks suggest racking; multiple radiating cracks suggest a point of settlement).

Install monitors at the cracks that will tell you the most:

The widest crack (most active).

A crack near a corner of the building (where settlement of one footing will show first).

A crack above the largest opening (door or large window; openings concentrate stress and reveal movement early).

A crack at a foundation-to-veneer interface (separation between rigid foundation and flexible veneer indicates relative movement).

For a typical residential job with multiple cracks, install 2 to 4 monitors at strategic locations rather than one per crack.

Surface preparation

The monitor adheres to the substrate. Adhesion failure invalidates the reading. Three substrate types in brick veneer:

Brick face: clean, dust-free, dry. Wire brush any loose paint, efflorescence, or surface contamination. Wipe with denatured alcohol; allow to dry.

Mortar joint: similar prep. Mortar provides slightly less reliable adhesion than brick face; preference is to anchor monitor pieces to brick faces on each side of the crack.

Painted brick: scrape any loose paint flakes. The monitor adheres to the paint surface; if the paint is sound, adhesion is acceptable. Inform the homeowner that monitor removal will leave a paint mark.

Stone veneer: clean as for brick. Smooth stone faces give better adhesion than rough rubble stone; on rough stone, find the flattest available surface near the crack.

Installation

Step 1: Mark the alignment. Position the monitor across the crack as it will be installed. Mark the four corner positions on the substrate with pencil or chalk. The monitor must be square to the crack (one axis of the grid parallel to the crack) for accurate movement reading.

Step 2: Mix the adhesive. Most installations use a two-part epoxy (Loctite 5-Minute Epoxy, Devcon 5 Minute Epoxy, or a structural-grade methyl methacrylate). Pre-mix small batches; do not mix more than will be used in 3 to 5 minutes of working time.

Step 3: Apply adhesive to the monitor backside. A small bead at each of the four corners of each monitor piece is sufficient. Avoid adhesive in the middle of the monitor (would interfere with monitor flexibility under movement).

Step 4: Position the monitor. Place the two pieces in their pre-marked positions. The grid pattern should align at the zero reference point: the cursor on one piece centered over the zero on the other piece's grid.

Step 5: Hold for cure. Tape the monitor in place with painter's tape if 5-minute epoxy is used; hold for 5 to 10 minutes minimum. Verify alignment before tape removal.

Step 6: Document the initial state. Photograph the monitor with a ruler in frame for scale, the date written on a piece of tape adjacent to the monitor, and the location of the monitor on the building (wide shot showing the monitor in context). The initial reading is the zero datum.

References

• IRC 2021 Section R403 Foundations (referenced for foundation design and movement context)
• ACI 224R Control of Cracking in Concrete Structures (referenced for crack interpretation in structural contexts)
• ICC ES Acceptance Criteria for Crack Monitoring Devices (referenced for monitor selection)
• ASTM D7012 Standard Test Methods for Compressive Strength and Elastic Moduli of Intact Rock Core Specimens (referenced for substrate evaluation)
• Avongard Technical Data Sheets for Standard Telltale and Corner Telltale current edition
• US Army Corps of Engineers EM 1110-2-1908 Instrumentation of Embankment Dams and Levees (crack monitoring methodology, transferable to building contexts)