Foundation Crack Monitoring Log Calculator

Inputs

Example Data Table

Formula Used

• Total width change: ΔW = W_last − W_first
• Absolute change: |ΔW| = |W_last − W_first|
• Average movement rate: R_avg = |ΔW| ÷ Days
• Segment rate: R_seg = |W_i − W_i−1| ÷ Days_i
• 90‑day projection: W₉₀ = W_last + (R_avg × 90)

How to Use This Calculator

1. Identify one crack and mark consistent measurement points.
2. Measure width with a crack gauge or feeler set.
3. Optional: record length and context notes each visit.
4. Add at least two dated readings in the log table.
5. Set optional alert thresholds to match your policy.
6. Click Calculate to see rates, classifications, and timing.
7. Export CSV/PDF for maintenance records or consultation.

Establishing a Reliable Baseline

Accurate monitoring starts with a baseline. Clean the crack, choose fixed reference points, and photograph the area with a scale. Measure width at the same station using a crack gauge or feeler set. Record the reading date, the unit used, and any adjacent distress such as spalling or dampness. A consistent baseline reduces noise and makes later comparisons meaningful for decisions, and note finishes or cracks.

Setting Reading Frequency and Context

Inspection frequency should match risk. For stable hairline cracks, monthly to quarterly checks can be enough. For wider cracks or active movement, weekly or biweekly readings capture short-term changes. Always log environmental context like heavy rain, freeze-thaw cycles, excavation, or plumbing leaks. These conditions often correlate with movement. Notes help separate seasonal expansion from progressive settlement trends. Include interior symptoms like sticking doors and drywall gaps.

Evaluating Movement Rates and Spikes

Movement rate is calculated from width change over time. Compare the average rate across the full window with segment rates between consecutive readings. Segment rates reveal bursts of movement that an overall average can hide. If a single interval shows rapid change, review site conditions and confirm measurement technique. Recheck within a few days, and verify tools are seated consistently at the same mark before logging.

Applying Thresholds and Escalation Rules

Thresholds convert measurements into actions. Use a width alert to flag cracks that reach a policy limit, and a rate alert to flag accelerating behavior. This calculator classifies width and movement with practical bands, then recommends a follow-up interval. Treat the projection as planning only, not prediction. When alerts trigger, document the location clearly, monitor drainage, and consult a qualified professional promptly to reduce water-related movement.

Producing Records Professionals Can Use

High-quality records reduce cost and delay when escalation is needed. Keep readings in chronological order, include the exact crack location, and attach photos from the same angle. Record repairs, drainage changes, nearby loading changes, and any observed leaks. Export CSV or PDF outputs for contractors, engineers, or insurers. A clean log supports diagnosis, prioritizes remediation, improves communication, and protects accountability for future owners during future evaluations.

FAQs

How often should I record crack readings?

Use monthly checks for stable hairline cracks. Use weekly or biweekly checks for wider cracks or active movement. Increase frequency after storms, freezes, plumbing leaks, or nearby excavation to capture short-term changes.

What tools are best for measuring crack width?

A crack gauge card, feeler gauges, or a microscope gauge can work. Pick one method and use it consistently. Mark a fixed station on the crack so each reading repeats the same point.

Why does the calculator use both average and segment rates?

Average rate summarizes long-term movement. Segment rates show bursts between two dates that the overall average can hide. If one segment spikes, recheck measurements and document site conditions.

What crack width or movement rate is considered serious?

Thresholds vary by material and context. As a practical guide, rapid widening or widths in the moderate-to-severe range deserve prompt review. Use your alert settings to match local standards or engineer guidance.

Can I use this log for insurance or engineering reports?

Yes. A dated log with photos, notes, and exported tables helps professionals review trends efficiently. Keep records of repairs and drainage changes so reviewers can link movement to site events.

Does the 90-day projection predict the future accurately?

No. It is a simple linear planning estimate based on your average rate. Use it to schedule inspections, not to forecast damage. If conditions change, update readings and recalculate.

Important Notes

• This tool supports documentation and trend awareness, not diagnosis.
• Use the same tools and lighting to reduce measurement noise.
• If cracks widen quickly, become offset, or leak, seek help.