Crawl Space Calculator Project Checklist

Introduction

The most expensive time to discover a crawl space defect is after the access is closed — every fix then means re-entry, re-work, and often re-buying material. This checklist is the final verification pass before close-up: walk it with a headlamp and a hygrometer, check every item, and fix what’s wrong while it’s still easy to reach.

Run it against the quantities from the Crawl Space Calculator — the barrier coverage, vent count, insulation area, and dehumidifier sizing you planned with are the standards you verify against. Use it yourself for DIY work, or walk it with the crew leader before releasing final payment on pro work.

Moisture and Water

• No standing water. After the next rain (or a hose test), the floor is damp at most — no puddles. If water stands, drainage isn’t solved; nothing else on this list matters yet. See the pro tips guide.
• Exterior water managed: downspouts discharge 6+ ft (1.8 m) from the foundation; grade slopes away; gutters clear.
• Sump (if installed): basin at the low point, pump cycles on test, discharge routed to daylight or storm, sealed lid in encapsulated spaces.
• Vapor barrier complete: full floor coverage with no exposed soil — check corners, behind piers, and under equipment.
• Seams lapped and taped: 6–12 in (150–300 mm) laps (12 in on traffic paths), every seam taped with poly-rated tape, no lifted edges.
• Wall turn-up: barrier runs 6–12 in (150–300 mm) up the foundation walls, fastened — the wall-floor joint sealed.
• Piers and penetrations wrapped: every pier wrapped and taped; every pipe gets a taped collar with no raw cut edges.
• No tears or punctures: walk every traffic path; patch any damage with a poly patch lapped 12 in (300 mm) all around.

Ventilation or Sealing (Strategy-Dependent)

If vented:

• Vent count matches the plan: net free area ≥ floor area ÷ 150 — for 1,200 ft² (111.5 m²), 8 ft² (0.74 m²) net free. Count installed vents × each vent’s net free rating.
• Vents distributed around the perimeter, within ~3 ft (0.9 m) of each corner — no dead-air pockets.
• Screens intact on every vent (pest entry check).

If sealed:

• Every vent closed and sealed — mechanically with foam board + sealant, not stuffed with batts. Shine a light from outside at night; no light leaks in.
• Rim joists sealed and insulated — caulked joints, insulation in place, the most common air-leak path closed.
• Dehumidifier running: correctly sized to volume (70–90 pint/day for ~3,600 ft³ / 102 m³), humidistat set, condensate draining (verify water actually flowing), not sitting in a pan.
• Hygrometer installed and reading — baseline logged before close-up.

The vent math is derived in the formula guide; the strategy trade-offs in the complete guide.

Insulation

• Vented — floor batts: full contact with the subfloor everywhere (no gaps, no sagging), supported every 18–24 in (450–600 mm), correct R-value for the climate zone, not compressed.
• Sealed — wall foam: continuous coverage of the planned wall area (perimeter × height — 420 ft² / 39 m² for the 140 ft × 3 ft example), mechanically fastened, joints tight, termite inspection gap left per local requirements.
• Rim joist: insulated in both strategies — this junction is too often skipped.
• No insulation over water stains or damp framing — if it’s wet, the moisture problem isn’t solved; stop and diagnose.

R-value targets by zone are in the material guide.

Pests and Access

• All penetrations sealed: plumbing, electrical, ducts — no gaps a mouse can use (if a pencil fits, a mouse fits).
• Access opening: meets the ~18×24 in (450×600 mm) minimum (confirm locally), opens freely, closable and — in sealed spaces — sealed and insulated when closed.
• No stored organic material: no cardboard, no scrap lumber left behind — food and harborage for pests.
• Debris cleared: construction offcuts, old insulation, and trash removed — inspectors and future service techs need clear paths.

Documentation Before You Close Up

• Photos: barrier seams, pier wraps, insulation, dehumidifier setup, sump — dated photos prove the work for resale, warranty, and insurance.
• Product records: liner thickness, foam R-value, dehumidifier model and capacity — keep data sheets with the house files.
• Baseline hygrometer reading logged with the date.
• Contractor sign-off (pro work): walk the checklist with the crew leader; hold final payment until every item passes. Warranty terms in writing.

Worked Example: Checking the 30 × 40 ft Space

For the 30 ft × 40 ft × 3 ft (9.144 m × 12.192 m × 0.914 m) sealed encapsulation — 1,200 ft² (111.5 m²) floor, 1,380 ft² (128.2 m²) of 20-mil poly ordered, 420 ft² (39 m²) of wall foam, 90-pint dehumidifier:

1. Barrier: 1,380 ft² installed with 12 in laps — measure two or three laps with the tape; verify the wall turn-up runs a full 12 in (300 mm) and is fastened.
2. Seams: every seam taped — run a hand along each one feeling for lifted edges.
3. Vents: all sealed — night light-leak test from outside.
4. Foam: 420 ft² of wall covered — pace the perimeter (140 ft / 42.7 m) confirming no bare stretches; termite gap visible at the top.
5. Dehumidifier: running, draining, humidistat at 55%; hygrometer placed centrally, reading logged.
6. Photos + paperwork filed before the access closes.

Related Guides

• Pro Tips — the installation techniques this checklist verifies.
• Common Mistakes — what the checklist catches.
• Code Compliance — the inspection version of this pass.
• Material Guide — the specs being verified.
• DIY vs. Pro — using the checklist at contractor handoff.

Frequently Asked Questions

When should I run this checklist?

After all work is installed but before the access opening is closed for the last time — and before releasing final payment on contractor work. Schedule it as its own task, not squeezed into the end of install day.

What humidity reading should I see at close-up?

There’s no instant pass/fail — log the baseline reading and date, then check seasonally. Sustained readings under 60% relative humidity indicate the strategy is working; rising readings mean something needs attention.

How do I check vent seals from outside?

At night, have someone shine a bright light at each sealed vent from outside while you watch from inside — any light leak is an air leak. Seal it with foam board and sealant, not insulation stuffing.

Should I photograph the work?

Yes — dated photos of seams, wraps, insulation, and equipment prove the work for future buyers, warranty claims, and insurance. Once the access closes, photos are the only record.

What if the checklist finds standing water?

Stop — nothing else on the list matters until drainage is solved. Water intrusion overrides barrier, insulation, and dehumidifier plans alike. Diagnose the source (exterior first) and fix it before proceeding.

Can I use this checklist for a contractor’s work?

That’s one of its main purposes — walk it with the crew leader before final payment. Every item is observable and specific, which makes it a fair, concrete basis for sign-off or punch-list items.

Get Your Number

A checklist is only as good as the numbers behind it — verify your quantities in the Crawl Space Calculator, walk every item above with a headlamp before close-up, and file the photos and product records with the house files. The crawl space you never have to re-enter is the one that was verified before it closed.

Disclaimer: This checklist is general planning guidance, not a substitute for professional inspection. Calculator results are planning estimates based on the dimensions you enter. Consult a licensed professional or your local building authority for moisture, structural, pest, or code-related decisions.