| Structure | Perimeter (m) | Small gaps | Medium gaps | Large openings | Vents | Pipes | Clutter | Typical outcome |
|---|---|---|---|---|---|---|---|---|
| Tool shed | 34 | 6 | 2 | 1 | 2 | 1 | Medium | Medium risk, seal door sweep and vent mesh. |
| Greenhouse | 48 | 10 | 3 | 0 | 4 | 2 | Low | Medium risk, focus on frame joints and pipes. |
| Chicken coop | 28 | 8 | 4 | 2 | 1 | 0 | High | High risk, prioritize large openings and feed storage. |
Step 1: Convert observations into points.
- GapPoints = small×1.0 + medium×2.0 + large×4.0
- OpeningPoints = vents×1.5 + pipes×1.2 + doors×1.0 + drains×1.3
- SitePoints = wood×1.2 + compost×0.9 + feeders×1.6 + petFood×2.0 + vegetation×2.0
- ClutterPoints = clutterLevel(0–3)×1.5
- MoisturePoints = standingWater×1.0
Step 2: Normalize by inspected perimeter.
PerimeterFactor = √(perimeter ÷ 40). Reference perimeter is 40 meters.
Step 3: Calculate the index and risk.
Entry Point Index = (GapPoints + OpeningPoints + SitePoints + ClutterPoints + MoisturePoints) × PerimeterFactor.
- Walk the full perimeter at dusk with a flashlight.
- Count gaps by size band and note vents, pipes, drains.
- Record cover sources: clutter, wood piles, feeders, feed.
- Enter counts, then calculate your Entry Point Index.
- Fix top priorities first, then re-run after repairs.
- Use the target score to plan your next inspection.
Gap sizing and access thresholds
Most garden rodent issues start with measurable openings. Openings around 6–12 mm can admit small mice, while 13–25 mm gaps increase repeat entry and nesting likelihood. This calculator weights large openings highest because they usually indicate broken panels, missing bricks, or failed thresholds. Record counts by size band, then re-check after door-sweep replacement, timber shrinkage, or soil settling.
Vents, utilities, and drain routes
Vents, pipe penetrations, and floor drains form predictable corridors. Each vent or drain adds points because airflow and moisture often accompany these paths. Practical upgrades include metal mesh with tight fasteners, durable collars around pipes, and intact drain grates. For inspection, trace each utility line 0.5–1.0 m in every direction to find secondary gaps created by vibration or cracked mortar.
Garden pressure factors near structures
Food and cover raise entry pressure even when buildings are sound. Seed spill at bird feeders, accessible pet or poultry feed, and unmanaged compost can multiply nightly visitation. The model adds extra points for feed exposure and vegetation contact because climbing and bridging routes reduce the effort needed to test edges. Keep wood piles elevated and at least 1 m away, and reduce clutter within a 2 m perimeter strip.
Interpreting the Entry Point Index
The index converts observations into a single score, then adjusts by perimeter using a square-root factor. This avoids overstating risk for larger buildings while still reflecting more edge length. Use the risk label to prioritize: low means monitor, medium means systematic sealing, high means urgent exclusion plus sanitation. Re-run weekly; a 30–50% reduction typically indicates effective repairs.
Planning time, materials, and proof
Estimated hours and material quantities help you plan a realistic sealing session. Sealant tubes cover linear cracks, mesh covers openings, and steel wool helps pack tight gaps before sealing. Export the CSV or PDF after each inspection to document progress, share tasks, and compare seasons. Pair scores with simple evidence, such as droppings counts or chew marks, to validate improvements.
1) What perimeter should I enter?
Use the outer edge you can physically inspect: shed base, greenhouse frame, coop walls, or a continuous fence line. If you inspect multiple structures, calculate them separately for clearer priorities.
2) How do I count gaps accurately?
Walk slowly with a flashlight, then probe edges with a ruler or coin for size. Count distinct openings, not long cracks; long cracks can be recorded as multiple gaps if they vary in width.
3) Why are large openings weighted more?
Large openings usually permit easier entry, faster movement, and greater repeat use. They also signal structural failure that can expand quickly with weather and wear, so fixing them yields bigger score reductions.
4) Does a low score guarantee no rodents?
No. The score estimates access likelihood from visible conditions. Activity can still occur from temporary doors left open, nearby burrows, or seasonal food spikes. Use signs like droppings and gnawing to confirm.
5) How often should I re-run the calculator?
Run it after any repair, storm, pruning event, or layout change. Otherwise, weekly checks during peak seasons are useful. Track reductions; consistent drops usually mean exclusion work is effective.
6) What materials work best for exclusion?
Use metal mesh for vents and drains, durable sealant for cracks, and tight door sweeps for thresholds. Steel wool can pack small gaps before sealing. Avoid foam alone; it can be chewed through.