Waterproofing comparison
Crawl Space Encapsulation vs Vapor Barrier: Cost Comparison
These two get quoted against each other and they are not the same scope. A vapor barrier is plastic on the ground. Encapsulation is a sealed system with the walls covered, vents closed and humidity controlled.
Full encapsulation
$5,000 to $15,000
Vapor barrier only
$1,200 to $4,000
| Feature | Full encapsulation | Vapor barrier only |
|---|---|---|
| Typical cost | $5,000 to $15,000 | $1,200 to $4,000 |
| Ground covered | Yes | Yes |
| Walls covered | Yes | No |
| Vents sealed | Yes | No |
| Humidity control included | Usually a dehumidifier | No |
| Liner thickness | Heavy, reinforced | Often thin sheeting |
| Effect on floor comfort | Noticeable | Small |
| Addresses standing water | No, drainage does | No |
Full encapsulation
- Controls humidity year-round rather than only reducing soil evaporation
- Warmer floors above and often lower energy use
- Discourages mold, pests and wood decay
- Heavy reinforced liner survives being walked on
- Several times the cost of a barrier
- Sealing vents is a code question in some jurisdictions
- Combustion appliances in the crawl space need careful assessment
- The dehumidifier is an appliance that needs power and servicing
Vapor barrier only
- Far cheaper
- Meaningfully reduces moisture rising from soil
- Simple, with nothing to maintain
- A reasonable first step in a dry crawl space
- Does nothing about humid outside air entering through vents
- Thin sheeting tears when anyone works in the space
- Walls stay exposed
- Often quoted as if it were encapsulation
The verdict
Fix water first. Standing water, a failing gutter or ground sloping toward the house make both of these a waste of money until corrected. If the crawl space is dry and the problem is soil moisture, a proper vapor barrier is a sensible and cheap improvement. If humidity stays high through summer, if there is musty odor reaching the house, or if there is wood decay or mold, full encapsulation with humidity control is the appropriate scope. If any fuel-burning appliance is located in the crawl space, sealing it is a combustion air and carbon monoxide question for a professional.
Sealing a crawl space changes the pressure regime under the house, which is also the mechanism radon mitigation relies on: our RadonAway RP145C radon fan review explains why fan sizing needs a professional diagnostic rather than a catalogue.
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View on AmazonFrequently asked questions
Is crawl space encapsulation worth the cost?
In humid climates with a persistently damp crawl space it often is, because it addresses moisture that is otherwise feeding mold, wood decay and pests, and it usually improves floor comfort and energy use above. In a dry crawl space in an arid climate it is a much weaker case, and a vapor barrier may be all that is needed. The deciding evidence is measured humidity over a season, not a sales visit.
Should crawl space vents be sealed?
Sealing vents is standard in a proper encapsulation, on the reasoning that in humid weather outside air entering a cool crawl space condenses and makes things worse. It is also a code question that varies by jurisdiction, and it interacts with any combustion appliance located in the space, which needs air. Do not seal vents in isolation without addressing humidity control and combustion air.
What thickness vapor barrier do I need?
Thin sheeting tears the first time anyone crawls on it, which is why encapsulation systems use heavy reinforced liners. If you are having a barrier installed as a standalone job, ask what thickness is quoted and whether seams are taped and the liner is fastened at the walls. A loose sheet of thin plastic laid on the soil is not the same product as a properly detailed barrier.
I have mold in my crawl space. What should I do first?
Find the moisture source, because mold is a symptom. That usually means gutters, grading, plumbing leaks or groundwater. Remediation without fixing the water simply postpones the problem. Where the affected area is significant, use a remediation contractor who follows recognised industry guidance, and be wary of anyone who inspects, diagnoses and sells the remediation without an independent assessment.