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Crawl Space Inspection Checklist: Moisture Structure and Vents (Free Printable PDF)

Fillable under-floor crawl inspection: access, vapor barrier, vents, framing, insulation, pests and ducts. Print blank or save a filled PDF.

Inspections Fillable form · 9 sections · 46 checks Download filled or blank PDF and CSV Cross-checked against IRC R408, InterNACHI SOP, and ASHI SOP · Last verified Sep 16, 2026

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Fill this on screen, then download a PDF or CSV. Download a blank copy to complete by hand. Answers stay in this tab only. The next visitor sees a blank form. This is a visual under-floor crawl inspection of a US house: access, ground vapor cover, vents or sealed-space conditioning, joists and piers, insulation, visible pests and debris, plumbing, and ducts. It is not a full foundation, slab, or basement walk. Mark N/A on items the house does not have.

  • 9 sections
  • 46 checks
  • Blank for each visitor

Form details

Property

This is a visual template, not a licensed home inspection report and not a municipal code inspection. Adopted residential codes vary by state and city. InterNACHI asks you to state the crawl access location. ASHI asks you to state the methods used to inspect the under-floor space.

11 fields
Property

IRC R408.1: the under-floor space must follow vented R408.2 or unvented R408.3. Identify which system you are looking at before you mark vents or a sealed-space fan.

A concrete crawl floor has no dirt-cover lines. Exposed earth without a cover is a moisture item, not an automatic code fail on every older house.

InterNACHI 3.3: describe the location of the access to the under-floor crawl space. Interior hatch, exterior door, or more than one opening.

ASHI current text: not required to enter with less than 24 inches of vertical clearance or an opening smaller than 16 by 24 inches. ASHI 2026 approved text (not yet in force): 30 inches vertical and 30 inches horizontal, or an opening smaller than 18 by 24 inches. InterNACHI: do not enter if it is not readily accessible or looks unsafe. Record the method even when you stay out.

Optional. Useful if you later count vents. IRC R408.2 uses under-floor area for net vent area. Leave blank if you did not estimate.

Dry, raining, or recent heavy rain. Wet soil after a storm is not the same as standing water on a dry week.

Inspection station

Access and entry

Record the opening location and method in Property even if you do not enter. InterNACHI and ASHI are not required to enter a blocked, unsafe, or not readily accessible crawl.

7 items
Access and entry

Crawl access opening present and not blocked

IRC R408.4: access shall be provided to all under-floor spaces. Stored items, a locked hatch you cannot open, or a buried exterior door means you cannot complete the rest of this form. Write what blocked you in Notes.

Crawl access opening present and not blocked: OK, Defect, or N/A

Opening size recorded; floor or wall minimum checked if you measured

IRC R408.4: floor access not smaller than 18 by 24 inches; perimeter-wall access not less than 16 by 24 inches. Write the measured size in Notes. Do not invent a fail if you did not measure. ASHI current entry limit uses 16 by 24 inches; the 2026 approved text uses 18 by 24 inches.

Opening size recorded; floor or wall minimum checked if you measured: OK, Defect, or N/A

Below-grade wall access has an areaway, with the bottom below the threshold

IRC R408.4: where any portion of through-wall access is below grade, an areaway not less than 16 by 24 inches is required, and the bottom of the areaway shall be below the threshold. Mark N/A on an interior floor hatch or an above-grade wall door.

Below-grade wall access has an areaway, with the bottom below the threshold: OK, Defect, or N/A

Exterior wall access is not located under a door to the residence

IRC R408.4: through-wall access openings shall not be located under a door to the residence. Mark N/A if the only access is an interior hatch.

Exterior wall access is not located under a door to the residence: OK, Defect, or N/A

Hatch or door usable: opens, latches, and is not badly decayed or rusted through

InterNACHI 3.9: do not break the weather seal on an access cover you do not need to open. A missing door, a collapsed hatch, or a cover that will not stay closed is a defect. Weatherstripping and insulation on the door are good notes, not a visual Pass/Fail in InterNACHI or ASHI.

Hatch or door usable: opens, latches, and is not badly decayed or rusted through: OK, Defect, or N/A

Crawl entered, or the reason for viewing from the opening only is recorded

ASHI current: not required to enter with less than 24 inches of vertical clearance or an opening smaller than 16 by 24 inches. ASHI 2026 approved text: 30 inches vertical and 30 inches horizontal, or smaller than 18 by 24 inches. InterNACHI: do not enter if entry could cause damage or pose a hazard. Standing water, sewage, or exposed live wiring is a stay-out reason.

Crawl entered, or the reason for viewing from the opening only is recorded: OK, Defect, or N/A

Access provided to each separate under-floor bay you could reach

IRC R408.4: access shall be provided to all under-floor spaces. A blocked mid-span wall or a second crawl you could not enter belongs in Notes. InterNACHI is not required to move stored items or debris.

Access provided to each separate under-floor bay you could reach: OK, Defect, or N/A

Inspection station

Moisture and vapor barrier

Look at soil, the plastic cover, stem walls, and the underside of the floor. Do not fail a house on one overlap number. Model IRC unvented text uses 6 inches; DOE weatherization uses at least 12 inches; DOE Building Science Education uses 6 to 12 inches.

8 items
Moisture and vapor barrier

No standing water, active seepage, or wet soil in the crawl

InterNACHI 3.3: report observed indications of active water penetration. Damp earth after a storm is a note. Puddles, a wet cove, or rust at the base of a pier on a dry day is a defect.

No standing water, active seepage, or wet soil in the crawl: OK, Defect, or N/A

No signs that groundwater or trapped surface water sits near the crawl floor

IRC R408.6: if the groundwater table can rise within 6 inches of the finished floor at the perimeter, or the site does not drain, raise the interior grade or provide an approved drain. Water stains, silt lines, and efflorescence are clues. This is visual only.

No signs that groundwater or trapped surface water sits near the crawl floor: OK, Defect, or N/A

Dirt floor has a ground cover (plastic or Class I vapor retarder) if the earth is exposed

DOE: cover exposed dirt with at least 6-mil polyethylene. IRC R408.3 (unvented): continuous Class I retarder over exposed earth. A missing cover on bare soil is a defect on a modern sealed crawl and a moisture note on an older vented crawl. Mark N/A on a concrete crawl floor.

Dirt floor has a ground cover (plastic or Class I vapor retarder) if the earth is exposed: OK, Defect, or N/A

Ground cover reaches most of the exposed earth you could see

DOE weatherization: coverage as close to 100 percent as is reasonably possible. Report large bare patches, rolled-up sheets, or a cover that stops short of walls. InterNACHI is not required to move or disturb vapor retarders.

Ground cover reaches most of the exposed earth you could see: OK, Defect, or N/A

Cover not torn, pulled off piers, or left in a pile

Holes, missing pieces around pipes, and sheets that have blown off the soil let ground moisture in. Patch notes belong here. Do not lift the plastic to look under it.

Cover not torn, pulled off piers, or left in a pile: OK, Defect, or N/A

Edges turned up at stem walls and piers; seam laps noted, not failed on one number

IRC R408.3 (unvented): joints overlap 6 inches and are sealed or taped; edges not less than 6 inches up the stem wall. DOE weatherization: overlap at least 12 inches and extend 6 inches up walls, piers, and columns. DOE Building Science Education: lap 6 to 12 inches. Those numbers disagree. Report missing turn-up, open seams, or a cover that stops at the soil. Do not mark Defect only because a lap is 6 inches instead of 12.

Edges turned up at stem walls and piers; seam laps noted, not failed on one number: OK, Defect, or N/A

No ponded water sitting on top of the vapor cover

Water on the plastic can be condensation, a leak, or poor site drainage. IRC R408.3 asks unvented seams to be sealed; DOE weatherization asks you not to block established drainage. Describe what you see. A small dry stain can stay a note.

No ponded water sitting on top of the vapor cover: OK, Defect, or N/A

No widespread condensation, wet insulation, or musty decay on the floor underside

InterNACHI 3.3: report active water penetration and wood in contact with or near soil. Wet batts, beads of water on pipes or ducts, and white fungus on joists belong here. InterNACHI is not required to determine the presence of mold.

No widespread condensation, wet insulation, or musty decay on the floor underside: OK, Defect, or N/A

Inspection station

Vents and sealed-space air

Mark vent lines N/A on a sealed unvented crawl. Mark sealed-space equipment N/A on a vented crawl. InterNACHI and ASHI are not required to determine the adequacy of ventilation.

7 items
Vents and sealed-space air

Moisture system matches what you marked in Property (vented or unvented)

Open foundation vents mean a vented crawl unless they have been sealed on purpose. Closed-cell foam on the walls plus a continuous ground cover plus a fan or dehumidifier is usually unvented R408.3. Mixed systems belong in Notes.

Moisture system matches what you marked in Property (vented or unvented): OK, Defect, or N/A

Foundation vents present, open to the crawl, and not buried or blocked

Mark N/A on an unvented crawl built to R408.3. Look for soil, insulation, or storage covering the opening. A vent that has been spray-foamed shut belongs on the unvented station, not here.

Foundation vents present, open to the crawl, and not buried or blocked: OK, Defect, or N/A

Vents near corners or placed for cross-ventilation, if you could see the layout

IRC R408.2: one ventilation opening within 3 feet of each external corner, unless a Class I ground cover is present and openings are placed for cross-ventilation. Do not invent a vent-count Pass/Fail unless you measured net-free area.

Vents near corners or placed for cross-ventilation, if you could see the layout: OK, Defect, or N/A

Net vent area not judged unless you measured it

IRC R408.2: not less than 1 square foot of net vent area per 150 square feet of under-floor area. With an approved Class I ground cover, the model allows 1 per 1,500. Coverings reduce net-free area. Mark OK if vents look open and you did not measure. Use Notes if you did the math. Mark Defect only if vents are missing or clearly sealed on a crawl that still depends on them.

Net vent area not judged unless you measured it: OK, Defect, or N/A

Vent screens or covers in place; openings not larger than 1/4 inch if you can see them

IRC R408.2: coverings with a least dimension not more than 1/4 inch. Missing screens, broken slats, or a hole that lets animals in is a defect. Operational louvers are allowed. InterNACHI is not required to determine ventilation adequacy.

Vent screens or covers in place; openings not larger than 1/4 inch if you can see them: OK, Defect, or N/A

Unvented crawl has a working exhaust, supply-air, or dehumidifier path if that is the system

IRC R408.3 also requires one of: continuous exhaust at 1 cfm per 50 square feet, conditioned supply at the same rate with a return path, an existing-structure plenum, or a dehumidifier sized to the manufacturer's specifications. Do not invent a pint or cfm fail unless the nameplate and area were both recorded. Mark N/A on a vented crawl.

Unvented crawl has a working exhaust, supply-air, or dehumidifier path if that is the system: OK, Defect, or N/A

Bathroom, kitchen, or dryer exhaust does not terminate in the crawl

ASHI inspects kitchen, bathroom, laundry, and clothes-dryer exhaust. InterNACHI 3.9 inspects those mechanical exhaust systems. A dryer or bath fan that dumps into the crawl wets the space. Mark N/A if no exhaust duct is in the crawl.

Bathroom, kitchen, or dryer exhaust does not terminate in the crawl: OK, Defect, or N/A

Inspection station

Under-floor structure

This station is joists, beams, piers, and the mudsill from below. It is not an exterior foundation-wall or slab walk. InterNACHI is not required to size or span-check the support system. ASHI is not required to offer an opinion on structural adequacy.

7 items
Under-floor structure

Joists and the underside of the subfloor: no heavy decay, collapse, or missing members

ASHI section 3 includes subfloor and floor joists. Look for soft wood, fungus, and holes under baths. A stain that is dry and firm can stay a note. This is visual only.

Joists and the underside of the subfloor: no heavy decay, collapse, or missing members: OK, Defect, or N/A

Beams and girders bearing at ends and not heavily decayed or split

ASHI lists beams and girders under floor structure. Check bearing pockets and midspan supports you can reach. Do not calculate span.

Beams and girders bearing at ends and not heavily decayed or split: OK, Defect, or N/A

Piers, posts, and columns bearing, reasonably plumb, and not decayed at the base

ASHI includes columns and piers. Look for a post off its pad, a crushed shim, or wood sitting in soil. InterNACHI is not required to identify spacing or adequacy of the support system.

Piers, posts, and columns bearing, reasonably plumb, and not decayed at the base: OK, Defect, or N/A

Mudsill or rim visible from the crawl: in place and not decayed

Report a missing plate where you expected one, insect galleries, or soft wood at the rim. InterNACHI is not required to identify size, spacing, or adequacy of foundation bolting. Mark N/A if the plate is hidden.

Mudsill or rim visible from the crawl: in place and not decayed: OK, Defect, or N/A

No wood-to-soil contact under the floor (form boards, debris, or settled grade)

InterNACHI 3.3: report wood in contact with or near soil. IRC R408.5: remove vegetation, organic material, leftover wood forms, and construction materials from the under-floor grade. A joist in dirt is a defect even if vents are open.

No wood-to-soil contact under the floor (form boards, debris, or settled grade): OK, Defect, or N/A

No cut, notched, or bored framing that looks like a structural or safety concern

InterNACHI 3.3: report cutting, notching, and boring that may present a structural or safety concern. Typical place: a joist under a bath or HVAC opening. Mark N/A if no framing is visible.

No cut, notched, or bored framing that looks like a structural or safety concern: OK, Defect, or N/A

No obvious sag or dropped bearing at a support you can see from below

A beam off its pocket, a pier that has punched into soil, or a bay that droops belongs here. Do not invent a slope Pass/Fail. No SOP states inches per foot for this visual form.

No obvious sag or dropped bearing at a support you can see from below: OK, Defect, or N/A

Inspection station

Insulation

InterNACHI 3.9 and ASHI insulation sections ask you to look at insulation in unfinished crawl spaces. Neither requires you to move, touch, or disturb insulation, or to state R-value.

5 items
Insulation

Insulation present at the floor or at the perimeter walls, as this crawl uses

Vented crawls usually insulate the floor. Unvented R408.3 crawls that use exhaust or supply air also insulate the perimeter walls. InterNACHI: report the general absence of insulation in unfinished spaces. Mark N/A only if the space is not meant to be insulated (rare). Write the type in Notes.

Insulation present at the floor or at the perimeter walls, as this crawl uses: OK, Defect, or N/A

Batts or rigid insulation still in place, not fallen over vents or onto the ground

Fallen fiberglass that blocks a vent or lies on wet soil is a defect. Gaps at the rim are a note. Do not pull insulation to look behind it.

Batts or rigid insulation still in place, not fallen over vents or onto the ground: OK, Defect, or N/A

Insulation not soaked, compressed into mud, or covered with debris

Wet batts do not dry in a closed bay. Compressed or filthy insulation is a condition note even if some R-value remains. InterNACHI is not required to identify composition or R-value.

Insulation not soaked, compressed into mud, or covered with debris: OK, Defect, or N/A

Type of insulation observed (write it in Notes)

InterNACHI 3.9: describe the type of insulation observed. Fiberglass batts, foam board, spray foam, or none. Do not guess R-value. ASHI is not required to identify composition or R-value.

Type of insulation observed (write it in Notes): OK, Defect, or N/A

If this is a vented crawl in a warm-humid climate, a facing or retarder on the insulation is noted, not failed from memory

IRC R408.8: in Climate Zones 1A, 2A, and 3A below the warm-humid line, a continuous Class I or II vapor retarder (max 1.5 perms) belongs on the exposed face of air-permeable floor insulation. Exception: unvented crawls under R408.3. If you do not know the climate zone, describe what you see and mark N/A or OK with a note. Do not invent a facing Pass/Fail.

If this is a vented crawl in a warm-humid climate, a facing or retarder on the insulation is noted, not failed from memory: OK, Defect, or N/A

Inspection station

Pests, debris, and wood contact

This is not a licensed pest or WDO inspection. InterNACHI is not required to determine the presence of rodents, insects, or mold. ASHI is not required to determine the presence of wood-destroying organisms. Report what is in plain view, plus debris the model code wants removed.

5 items
Pests, debris, and wood contact

Vegetation, organic debris, leftover wood forms, and construction trash removed from the grade

IRC R408.5: clean the under-floor grade of vegetation and organic material; remove wood forms and construction materials before occupancy. Stumps, cardboard, and scrap lumber hold moisture and insects.

Vegetation, organic debris, leftover wood forms, and construction trash removed from the grade: OK, Defect, or N/A

No stored lumber or debris acting as a wood-to-soil bridge

InterNACHI 3.3: report wood in contact with or near soil. A firewood pile or leftover form board that touches both soil and a joist is a defect. InterNACHI is not required to move stored items.

No stored lumber or debris acting as a wood-to-soil bridge: OK, Defect, or N/A

No visible mud tubes, frass, or galleries on framing you passed

Termite tubes on a pier, powder under a joist, or honeycomb galleries are reportable if you see them. This is not a pest inspection and not a treatment recommendation. Mark OK if none were in view. Mark N/A only if you never entered and could not see framing.

No visible mud tubes, frass, or galleries on framing you passed: OK, Defect, or N/A

No obvious nests, droppings, or chewed insulation at the path you crawled

A nest in a batt, droppings on the vapor cover, or a chewed dryer duct is a condition note. InterNACHI is not required to determine the presence of rodents. Do not handle droppings.

No obvious nests, droppings, or chewed insulation at the path you crawled: OK, Defect, or N/A

Vent and access openings reasonably screened against animals

Missing vent screens (also on the Vents station) and an unlatched exterior door are common entry points. A 1/4-inch covering is the IRC R408.2 model for vents. This line is about animals getting in, not net-free area math.

Vent and access openings reasonably screened against animals: OK, Defect, or N/A

Inspection station

Plumbing, ducts, and under-floor equipment

InterNACHI 3.6 reports active plumbing leaks. ASHI inspects supply, drain-waste-vent, sumps, heating and cooling distribution, and dryer exhaust. Mark N/A on equipment that is not in the crawl.

7 items
Plumbing, ducts, and under-floor equipment

Supply piping: no active leaks, heavy corrosion, or pipes sitting in soil

InterNACHI 3.6: report active plumbing water leaks observed during the inspection. Look at joints, valves, and the water heater if it is in the crawl. Do not operate shut-off valves.

Supply piping: no active leaks, heavy corrosion, or pipes sitting in soil: OK, Defect, or N/A

Waste and vent piping: no active leaks, sag into soil, or disconnected joints

ASHI inspects interior drain, waste, and vent systems. A belly in a waste line or a joint that has pulled apart is a defect. Do not run water unless you already did so from fixtures above and came down to look.

Waste and vent piping: no active leaks, sag into soil, or disconnected joints: OK, Defect, or N/A

HVAC ducts connected, not crushed, with insulation still on if the ducts are insulated

ASHI heating and cooling sections include distribution systems. A disconnected flex duct dumps conditioned air into the crawl and pulls crawl air back. InterNACHI is not required to determine the types of materials used in duct wrapping.

HVAC ducts connected, not crushed, with insulation still on if the ducts are insulated: OK, Defect, or N/A

Condensate, TPR, or appliance drains do not dump onto the soil or the vapor cover

A water-heater relief tube or an air-handler drain that ends on the crawl floor wets the space. Route notes belong here. Mark N/A if no such equipment is in the crawl.

Condensate, TPR, or appliance drains do not dump onto the soil or the vapor cover: OK, Defect, or N/A

Visible cables protected; junction boxes have covers; no open splices

Look only at what you pass. An open splice, a missing box cover, or a cable hanging in standing water is a defect. This is not a panel or service inspection. Do not touch energized parts.

Visible cables protected; junction boxes have covers; no open splices: OK, Defect, or N/A

Crawl sump or interior drain, if present: cover in place, no sewage or standing flood

Mark N/A if none. InterNACHI is not required to operate a sump with an inaccessible float. ASHI includes sump pumps and related piping. A missing lid or a pit full of waste is a defect.

Crawl sump or interior drain, if present: cover in place, no sewage or standing flood: OK, Defect, or N/A

Fuel piping in the crawl, if present: supported, not rusted through, no obvious leak smell

ASHI inspects fuel distribution systems. InterNACHI is not required to inspect or test for gas or fuel leaks. If you smell gas, leave and treat it as unsafe. Mark N/A if there is no fuel pipe in the crawl.

Fuel piping in the crawl, if present: supported, not rusted through, no obvious leak smell: OK, Defect, or N/A

Form details

Findings and sign-off

List every Defect line here. This worksheet is not a licensed inspection report, not a structural-engineer letter, and not an official code inspection.

5 fields
Findings and sign-off

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References

  1. InterNACHI Home Inspection Standards of Practice, sections 3.3 crawl space and structure, 3.6 plumbing, and 3.9 insulation and ventilation
  2. InterNACHI, Inspecting Under-Floor Crawl Spaces (2024 IRC Section R408 access, vents, vapor retarder, debris, and grade)
  3. ASHI Standard of Practice (current page): structure, plumbing, insulation, ventilation, dryer exhaust, and crawl entry limits
  4. ASHI Standard of Practice 2026 approved text (not yet in force): 30-inch crawl clearance and 18 by 24 inch opening
  5. International Residential Code 2024, Chapter 4 Foundations, Section R408 Under-Floor Space (GSA viewer)
  6. U.S. Department of Energy, Install or Repair a Crawl Space Vapor Retarder (6-mil cover, 12-inch seam lap, 6 inches up walls)
  7. DOE Building Science Education, Crawlspace Capillary Break at Crawlspace Floors (6-mil poly, 6 to 12 inch laps)

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