Standing water is a drainage problem before it is a liner problem. Check three conditions, then decide what the crawl space actually needs.
Outside firstthen the liner questionA wet crawl space is often a yard and downspout problem showing up under the house. A liner over that is a bag over a leak.
This check reads three crawl space conditions: standing water, whether a vapor retarder covers the soil, and whether wood touches soil or stays damp. Standing water points to drainage and grading before any liner.
You can type an encapsulation price from a bid; we never supply one. It does not test for mold, assess radon, or tell you to encapsulate.
Standing water, vapor, wood
Conditions you ticked. Encapsulation only if you type a dollar. Nothing is emailed.
—Conditions
—Encapsulation line
—What this page will not do
What this assumed—
Conditions you ticked, plus an optional dollar you typed. Not a product pitch. Outside water first. HyreFoundation does not encapsulate crawls.
The mechanism
There are two correct crawl spaces. Most bad ones are neither
The model code describes a vented crawl space and an unvented one, each internally consistent. The failure mode almost nobody names is the crawl space that is half of each. If you are not certain the space under your house is a crawl space at all, the foundation type identifier settles that first.
Source fact — the vented design. IRC R408 sets the ventilation requirement: "The minimum net area of ventilation openings is to be not less than 1 square foot for each 150 square feet of under-floor area."
The logic is that outside air carries away ground moisture faster than the ground supplies it. The ratio may be reduced to 1 square foot per 1,500 square feet where the ground surface is covered with a Class I vapor retarder, subject to the conditions in the section.
Source fact — the unvented design. "Ventilation openings are not required where the exposed earth is covered with a continuous Class I vapor retarder and one of the listed conditioning methods is provided."
And one of those listed methods: "One listed method is continuously operated mechanical exhaust ventilation at a rate of 1 cubic foot per minute for each 50 square feet of crawl space floor area."
Here the logic is the opposite: seal the ground off entirely, bring the space inside the building envelope, and condition it.
Our analysis — why the halfway version fails. A vented crawl space and a sealed conditioned one are two coherent designs. Half of each is not.
Adding a vapor barrier and leaving the vents open is common and is neither. Sealing the vents without a continuous ground barrier and a conditioning method is the version that grows mold.
And there is a season in which venting actively backfires. A crawl space is cool. In a humid summer, warm outdoor air drawn through open vents meets cool surfaces — ductwork, joists, the ground cover, the piers — and condenses on them.
That is not a leak. It is the ventilation strategy delivering moisture rather than removing it, which is precisely why the unvented approach exists as a recognized alternative rather than as a shortcut.
The practical consequence. Before anyone quotes you anything, establish which design your crawl space is meant to be. Then ask whether it actually is that.
A great many crawl spaces have drifted: a vapor barrier was added at some point by someone, and the vents were left as they were, and now the space has neither the airflow of the first design nor the conditioning of the second.
What this is not. It is not an argument for encapsulation. Both designs work when built as designs. It is an argument against buying half of one, which is the commonest thing sold in this space.
The two designs
Vented, unvented, and the half-built version in between
The last column is the useful one. Read it before pricing anything: it is where each design fails, and one of these columns is describing your crawl space right now.
Design
What the code asks for
The logic it runs on
How it fails, and what its absence means
Vented
The minimum net area of ventilation openings is to be not less than 1 square foot for each 150 square feet of under-floor area. The ratio may be reduced to 1 square foot per 1,500 square feet where the ground surface is covered with a Class I vapor retarder, subject to the conditions in the section.
Outside air removes ground moisture faster than the ground releases it. Works well in dry climates and in cold weather.
Fails in humid summers, when incoming warm air condenses on cool surfaces below. Also fails when vents are blocked by landscaping, stuffed with insulation, or closed "for winter" and never reopened. If your vents are obstructed, the design you have is not the design your house was built with.
Unvented / conditioned
Ventilation openings are not required where the exposed earth is covered with a continuous Class I vapor retarder and one of the listed conditioning methods is provided. One listed method: "One listed method is continuously operated mechanical exhaust ventilation at a rate of 1 cubic foot per minute for each 50 square feet of crawl space floor area."
Seal the ground off completely and bring the space inside the thermal and moisture envelope of the house. No outside air, so no imported humidity.
Fails when the ground cover is not continuous, when the conditioning method is absent or was switched off, or when water is still entering from outside. A sealed space with a moisture source and no air change is the worst of the three outcomes on this table.
The half-built version
Nothing. It is not a design.
None. Usually the residue of two different decisions made years apart by different people.
The most common condition and the least often named. Symptoms: plastic on the ground that does not reach the walls or is torn; vents open with a barrier down; vents sealed with no dehumidifier or supply air; insulation between joists that is damp, sagging or face-stapled the wrong way. Its absence from a proposal — nobody saying which design you are moving toward — is the single most informative gap.
Model code figures. The IRC is a model code. It has force only in the edition your jurisdiction adopted, with the local amendments that jurisdiction made.
Foundation chapters get amended more than most, because frost depth and soil are local facts. Confirm with your building department before relying on any figure here.
Crawl space provisions are amended locally more than most, and some jurisdictions have their own conditioned-crawlspace rules.
The sequence that gets skipped
Standing water is a drainage problem. A liner over it is a pond with a lid
Lining over standing water is the most expensive mistake available in a crawl space, and it is easy to make because the finished job looks so convincing.
Illustrative weighting, not data. A diagram of an argument rather than a measurement.HyreFoundation analysis, structured on IRC R405 and R408
Source fact. IRC R405 requires drains around below-grade foundations that enclose usable space, and exempts them in exactly one case: "A drainage system is not required where the foundation is installed on well-drained ground or sand-gravel mixture soils according to the Unified Soil Classification System, Group I soils."
The exemption is granted for ground that already drains, which tells you what the requirement is for.
Our analysis. Drainage is the requirement that relieves pressure. Membranes resist water; drains remove the head that pushes it. This is why a waterproofing sale with no drainage line item is the wrong shape of job, and why the cheapest genuinely effective work on most houses is above ground, in gutters and grade.
Applied to a crawl space. If there is standing water under your house, something is delivering more water to that ground than the ground can take away.
Covering it changes what you can see and changes nothing about the supply.
Worse, a sealed space with a live water source and no air change is the exact condition the unvented design depends on not existing.
Where the water usually comes from, and it is rarely exotic. A downspout discharging at the corner. A gutter that has not worked in three years. Grade that settled and now falls toward the house.
Irrigation on a timer soaking one elevation. A crawl vent sited below the surrounding soil level so the yard drains into it. Each of those is cheap to fix and none of them is a product.
Recommendation — the order. Stop the water arriving. Then give any water that still arrives somewhere to go. Then decide between the two designs and build one of them properly.
Doing that third step first is how people pay twice, and it is the order the market pushes because the third step is the one with a product attached.
The one exception worth naming. If the crawl space is below the surrounding grade and water genuinely arrives from the water table rather than from the roof, no amount of gutter work will solve it and a sump with a real outfall is a legitimate part of the answer.
That is a site fact someone should demonstrate, not assert.
The product
What "encapsulation" has to include to be worth buying
Encapsulation is a real technique with a real basis in the code. It is also a word applied to work ranging from a designed conditioned crawl space to plastic sheeting thrown on dirt, at prices that do not distinguish between them.
What the code version actually requires
IRC R408 permits the unvented approach on conditions: "Ventilation openings are not required where the exposed earth is covered with a continuous Class I vapor retarder and one of the listed conditioning methods is provided."
The two halves are both load-bearing — a continuous Class I vapor retarder on the exposed earth, and a conditioning method.
One listed conditioning method is mechanical: "One listed method is continuously operated mechanical exhaust ventilation at a rate of 1 cubic foot per minute for each 50 square feet of crawl space floor area."
Others involve conditioned air supplied to the space. The principle in every case is that the space is now inside the building and has to be treated like it.
So the test for a proposal is simple. Does it name a continuous ground cover, sealed and extended up the walls and around the piers? And does it name a conditioning method that will still be running in five years? If it names only the first, it is half a system.
The line items to look for
Water handled first, as its own priced line: exterior drainage, grade, downspouts, and a sump with a stated outfall if one is needed.
A continuous ground cover, with the thickness stated, seams sealed, terminated and sealed at the walls and around every pier and penetration. Continuity is the entire specification; a barrier with gaps is a barrier that has not been installed.
A named conditioning method, with equipment, capacity, power supply, and where the condensate goes. A dehumidifier draining into the space it is drying is not a design.
What happens to the existing insulation, which in a conditioned crawl is usually relocated from between the joists to the perimeter walls. Leaving damp batts up in the floor of a newly sealed space is a common and avoidable failure.
Combustion safety, if any fuel-burning appliance or its venting sits in or draws from the crawl space. Sealing a space that supplies combustion air is a safety question, not a moisture one, and it belongs to a qualified professional. Do not resolve it yourself and do not accept a vague answer.
Access and inspectability afterwards, so you can still see the ground and check for water. A space you cannot enter is a space nobody will look at again.
What we will not tell you
Whether to encapsulate. That depends on your climate, your water, your existing design and your ducts, and none of those are on this page. Plenty of crawl spaces are fine vented, and the correct outcome for a great many is "fix the downspouts, replace the torn ground cover, clear the vents, look again next summer".
What it should cost. We hold no dataset of crawl space jobs, bids or invoices, and we will not reprint the per-square-foot figures that circulate on lead-generation sites in order to look authoritative.
HyreFoundation does not encapsulate crawl spaces, does not install liners or dehumidifiers, does not inspect, and takes no referral fee from anyone who does.
Before anyone quotes you
What to look at, in order, with a flashlight
Go in only if it is safe to do so — adequate access, no standing water near wiring, no reason to suspect a gas or sewage issue, and someone who knows you are down there. If any of that is in doubt, photograph from the hatch and stop.
1
Is there standing water, and is it there today or only after rain?
The single most important observation, and the one that reorders everything below it. Standing water means drainage work comes first, before any liner is discussed.
2
Is there a ground cover, and is it continuous?
Not "is there plastic". Does it cover all the exposed earth, are the seams lapped and sealed, does it terminate at the walls, is it sealed around the piers, is it torn where people have crawled over it. Continuity is the whole specification.
3
Are the vents open, blocked, or deliberately sealed?
This tells you which design the space is currently attempting. Open vents plus a ground cover is the half-built version. Sealed vents with no conditioning equipment is the other half-built version, and the more dangerous one.
4
Is there conditioning equipment, and is it actually running?
A dehumidifier with a full bucket, an unplugged unit, a condensate line discharging onto the ground cover. If the space is sealed, the equipment is not optional and its condition is the design.
5
What state is the insulation and the wood in?
Sagging or fallen batts, dark staining, visible growth on joists or subfloor, soft or crumbling wood, or evidence of insects. Note and photograph. Do not disturb suspected growth, and do not attempt to identify it — that is a different profession.
6
Where are the ducts and the pipes?
Disconnected or crushed ducts, sweating cold lines, a condensate line dripping onto soil. Ductwork in a humid crawl space is a condensing surface and sometimes the moisture source people spend a year looking for.
7
Then go outside and walk the water
Gutters, downspouts, grade, irrigation, and whether any vent sits below the surrounding soil level. The water intrusion diagnostic walks the same ground as questions. This is the step most likely to change what needs buying.
The questions
What to ask the company standing at your crawl hatch
Every one of these has a short, checkable answer, and the last two are the sentences that should slow the conversation down.
"Which design am I ending up with — vented or unvented?"
A proposal that cannot answer this is not proposing a design. Both answers are legitimate; no answer is not.
"What is the conditioning method, and what happens to the condensate?"
Only relevant if the answer above was unvented — in which case it is not optional. Equipment, capacity, power, drainage destination.
"What are you doing about the water before the liner goes in?"
Priced as its own line so you can see it. If the answer is nothing and there is standing water, you are being sold a lid.
"How does the barrier terminate at the walls and the piers?"
Sealed, mechanically fastened, extended up the wall by a stated height. This is where continuity is won or lost and it is easy to inspect afterwards if you know to ask now.
"What happens to the existing floor insulation?"
In a conditioned crawl it usually moves to the perimeter walls. Leaving damp batts in the joists of a newly sealed space is a known failure and a cheap thing to get right.
"Is there any combustion appliance or vent in or drawing from this space?"
If yes, sealing the space raises a safety question that must be answered by a qualified professional before anything is closed up. Accept a specific answer, not a reassurance.
"We include a free mold test with the inspection"
Ask who performs it, who reads it, and who is paid for the remediation. Testing and remediation sold by the same party is a conflict of interest, and two states legislate against it. We do not assess mold.
"This price is only good while I am here"
The FTC’s standing home-improvement advice is to get it in writing and get more than one bid. A price that expires when the salesperson leaves is a fact about the sales process, not about the work.
Vocabulary
The words, defined as this trade uses them
Vapor retarder (Class I)
A material of very low permeance laid over exposed earth. IRC R408 allows the unvented approach where the exposed earth is covered with a continuous Class I vapor retarder and a listed conditioning method is provided. The word doing the work is continuous.
Encapsulation
A trade term, not a code term. At its best it is the unvented design built properly — continuous ground and wall cover plus conditioning. At its worst it is sheeting on soil. The price range does not reliably distinguish them, so the specification has to.
Conditioned crawl space
A crawl space brought inside the building envelope, sealed from outside air and served by a conditioning method — one listed option being continuous mechanical exhaust at 1 cfm per 50 square feet of floor area.
Net free area
The actual open area of a vent after the screen and louvre are accounted for, which is what the 150-to-1 ratio is measured against. It is considerably less than the size of the hole in the wall.
Perimeter wall insulation
Insulation applied to the crawl space walls rather than between the floor joists. The normal arrangement once the space is conditioned, because the thermal boundary has moved from the floor to the walls.
Condensing surface
Any surface cool enough for humid air to reach dew point against it — ductwork, cold water lines, the ground cover, piers. The reason summer venting can add moisture rather than remove it.
Footing drain
IRC R405: "Drains shall be provided around concrete or masonry foundations that retain earth and enclose habitable or usable spaces located below grade." The stone extends at least 1 foot beyond the footing and 6 inches above it.
Dampproofing vs waterproofing
These are two different code requirements, not two words for the same product. Which one applies is decided by the ground water condition at your site, not by the coating on the truck. A contractor who uses the words interchangeably is telling you something about the estimate.
Efflorescence
White crystalline salt deposit left where water has passed through masonry or concrete and evaporated. Evidence of past water movement, readable on a dry day months later — useful in a crawl space, where you rarely visit during the event.
Frost line
The local depth of ground freezing, published by your jurisdiction in IRC Table R301.2.
Exterior footings are to be placed not less than 12 inches below the undisturbed ground surface, and, where applicable, below the frost line specified for the locality. Both conditions apply and the deeper one governs.
Twelve inches is a floor, not a target: in a locality with a 42-inch frost line, 12 inches is nowhere near legal.
Limits
What this tool cannot do
Named blind spots, not a boilerplate disclaimer. Each is a real thing three dropdowns cannot see.
It cannot see whether your ground cover is continuous. "Yes, there is a vapor retarder" and "yes, there is a continuous, sealed, wall-terminated vapor retarder" are different facts, and the difference is the entire specification. Only your flashlight settles it.
It cannot identify mold or assess a health risk. Not from a form, not from a photograph, not at all. We do not assess mold, do not interpret reports, and are not clinicians.
If growth is visible, do not disturb it and get advice from someone whose job that is — and preferably not from the party who would be paid to remove it.
It cannot see your climate. Whether venting helps or harms in July depends on where you are, and this page holds no climate lookup. The mechanism is described above so you can apply it; the local answer is local.
It knows nothing about your soil or water table. RETRIEVAL FAILED — the USGS publications warehouse returned HTTP 403 to automated retrieval on 5 September 2026.
The map is named here as the national reference that exists; we did not read it, and we publish no figure from it.
For a site-specific answer the correct lookup is the USDA NRCS Web Soil Survey, and even that is a general soil context rather than a reason a particular crack exists.
It cannot assess structure. Soft or crumbling wood, sagging girders, failed piers, insect damage: outside what this page evaluates, and all of them change the priority. Those are for a licensed engineer, paid by you.
It has no price data and will not produce a number. We hold no dataset of crawl space work, and per-square-foot figures circulating elsewhere are marketing rather than measurement.
It cannot resolve a combustion safety question, and nothing on this page should be read as clearing one. Sealing a space that contains or supplies air to a fuel-burning appliance is a matter for a qualified professional, on site.
HyreFoundation does not encapsulate crawl spaces, does not inspect them, does not perform any of this work, and takes no referral fee from anyone who does.
That is why this page can end at "clear the vents, replace the torn sheet, fix the downspout, look again next summer" — which is the correct answer for a great many houses.
How this calculator works
There is no score that means "encapsulate." Three conditions write sentences. An optional dollar is labeled as yours:
if standing water: drainage and grading before a liner product
if no vapor retarder: a documented condition, not encapsulate-everything
if wood wet or in soil: decay and termite as much as moisture
if none of those: no red-flag answers, which is not a dry crawl
enc = the dollar you typed, labeled as not a national average
or "no encapsulation dollar entered"
never = not a specification to encapsulate. Outside water first.
Empty flags do not become a clean bill. The engine says so: no red-flag answers is not a dry crawl. Look, measure humidity if you have a meter, and fix water outside first.
HyreFoundation does not encapsulate crawls, does not inspect them, and does not repair foundations.
What each input means
Inputs on this tool, in the order they appear on the form.
Input
What it is actually asking
Standing water
Did you see a pond or a film on the crawl floor. Yes means drainage and grading first. A liner over a pond is a bag over a leak.
Vapor retarder
A sheet on the soil. Unknown is valid. No is a documented condition, not an order to encapsulate the whole crawl. Yes is not proof the assembly is detailed at the piers.
Wood
Sill, joists, posts in the dirt or chronically damp. Unknown is valid. Yes is decay and termites as much as a moisture product. No is what you saw that day, not a warranty.
Encapsulation ($)
Optional. A number from a bid. 0 means we will not invent one. The label in the result says you typed it.
Worked examples
Including one where the naive answer misleads, which is the example most calculators leave out.
No standing water, vapor and wood unknown, no dollar
Read: no red-flag answers. That is not a dry crawl. Look, measure humidity, and fix water outside first. Encapsulation line: no encapsulation dollar entered, we will not invent one. Never: not a specification to encapsulate. The useful next step is a look with a flashlight and a walk of the downspouts, not a liner brochure.
Standing water, no vapor retarder, wood yes, $8,000 typed
Read stacks three sentences: standing water is drainage and grading before a liner; no vapor retarder is a documented condition, not encapsulate-everything; wood in contact with soil is decay and termites as much as moisture. Encapsulation line: $8,000, the line you typed, not a national average.
The honest order is: get the water out and keep it out, then decide whether a soil cover or a sealed assembly is even the job. The $8,000 is a data point, not a diagnosis.
The one where encapsulate-everything misleads
A company that only sells encapsulation quotes a sealed crawl on a house whose downspouts still dump at the wall, with standing water after every storm. The naive reading is that plastic is the method.
Tick standing water yes. The engine puts drainage and grading before the product.
Leave the dollar at 0 if the only number you have is that pitch, or type it and read the label: you typed it, we did not invent a national average. Outside water first.
A liner over an active pond is the example this page exists to catch.
What changes the result
Each of the three condition dropdowns only adds a sentence. They do not multiply. They do not output a product. All-unknown or all-clear still refuses a clean bill.
The dollar field is independent. It never changes the condition paragraph. It only labels a number you brought. Changing it from 0 to 12,000 does not make encapsulation the right method. It makes the invoice visible.
Nothing on the form asks about radon, termites as a species, or relative humidity. Those are real questions. Folding them into a liner SKU would be the misleading product again.
Local considerations
Whether a closed crawl is common, whether vents are required, and how radon is handled are local. EPA radon guidance is national as a health message (test, you cannot see it) and still not a crawl design for your house. ICC crawl provisions are model code, not your inspector until adopted.
Soil under the crawl is local. NRCS Web Soil Survey is a general lookup. Onsite investigation is needed for engineering applications. We will not pretend a map unit is a reason to encapsulate.
When not to use this
Do not use this as a specification to encapsulate, a bid, or a reason to skip outside drainage. It cannot see the crawl.
Do not use "no standing water" as a dry crawl. You looked on one day. Humidity, wood moisture and the next storm are not on this form.
Do not use a typed encapsulation dollar as a national average or as a radon mitigation design. EPA says test for radon. This page will not treat a liner invoice as that test.
Do not enter a crawl you cannot get out of. HyreFoundation does not inspect crawls.
HyreFoundation does not encapsulate crawls. Matching is still being built. The inquiry form is not a dispatch line.
Usually because water arrives from outside: grade sloping toward the house, downspouts at the wall, poor site drainage or a high water table. Sometimes it is a plumbing leak. Walk the lot in the rain. The water intrusion diagnostic helps trace the source.
Do I need to encapsulate my crawl space?
Not automatically. Encapsulation is a designed assembly: a sealed liner, usually a dehumidifier or conditioning, sealed details at piers and walls, and a plan for existing moisture. Many crawl spaces work fine vented. Fix outside water first. See crawl space repair for the options.
What is a vapor retarder in a crawl space?
It is a sheet covering the exposed soil so ground moisture cannot evaporate into the crawl space. It is not the same as full encapsulation. A missing sheet is a condition to note, not an order to encapsulate everything.
Is wood touching the soil a foundation problem?
It is mainly a decay and termite problem. Sill plates, joist ends and posts that stay wet fail as wood, not as soil, so a sagging floor can be rot rather than settlement. Fix the water, then have someone look at the wood, not only at a liner brochure.
Should I vent my crawl space or seal it?
It depends on climate and detailing. IRC R408 allows both: a vented crawl space, or a sealed one with a continuous ground cover and conditioning. Opening vents in a humid climate can pull damp air in. Either way, fix outside water first.
Does crawl space encapsulation fix radon?
Not by itself. EPA says you cannot see or smell radon and testing is the only way to know the level. A crawl space can be a pathway. Test first, then talk to someone who does radon mitigation. A liner price is not a mitigation design.
Can I put down a crawl space vapor barrier myself?
On dry, accessible soil, a ground cover is a simpler job. Sealing a wet crawl space with standing water and wood in the dirt is a different one. Fix the outside water first, and do not treat a DIY sheet as a reason to skip the grading.
Does a wet crawl space mean my house is settling?
Not necessarily. Moisture can rot wood supports so the floor sags, which looks like settlement. Moisture can also move expansive clay. An engineer who does not sell repairs tells those apart. See why foundations move.
What should I ask a crawl space encapsulation company?
Ask what they will do about outside water, what they will do about wood touching soil, and whether the bid is a simple ground cover or a fully sealed assembly. Those are very different invoices.
Does HyreFoundation encapsulate crawl spaces?
No. We do not encapsulate, repair, inspect or survey, and matching with companies is still being built.
Sources and methodology
Figures dated 26 August 2026. Last reviewed .
Under-floor space: ventilation and unvented crawl spaces (IRC R408) (International Code Council, read via UpCodes, retrieved 2026-09-05. The 1-per-150 vent ratio, the reduced ratio with a Class I vapor retarder, the unvented option and the 1 cfm per 50 sq ft exhaust method. Model code only; adoption is local.)
Foundation drainage (IRC R405) and dampproofing/waterproofing (IRC R406) (International Code Council, read via UpCodes, retrieved 2026-09-05. The drainage requirement, its washed-gravel envelope dimensions, and the single exemption for well-drained Group I soils — cited here for the position that standing water is a drainage problem before it is a liner problem.)
International Residential Code, Chapter 4 Foundations (International Code Council, retrieved 2026-08-26. Model code for foundation spaces, including moisture and crawl provisions as adopted locally. Not a liner specification and not your city until adopted.)
Building America program (U.S. Department of Energy, retrieved 2026-08-26. Moisture, durability and crawl assemblies as building science. Not a product pitch and not a national encapsulation price.)
Radon (U.S. Environmental Protection Agency, retrieved 2026-08-26. Cited because crawls can be a radon pathway. Testing is the measurement. A liner dollar on this form is not a mitigation design.)
A brief guide to mold, moisture and your home (U.S. Environmental Protection Agency, retrieved 2026-08-26. Fix moisture. Not a reason to skip outside drainage, and not a structural opinion.)
Web Soil Survey (USDA Natural Resources Conservation Service, retrieved 2026-08-26. General soil and drainage context at an address. Onsite investigation is needed for engineering applications. Not a crawl design.)