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Seal the ground, dry the house, drop the heating bill

Crawl Space Encapsulation in Portland, OR

We seal your crawl space floor and walls with a 20-mil vapor barrier, insulate the rim joists, and hold humidity under 55%. A damp dirt crawl space becomes clean, dry space you can actually use.

  • Danielle Whitcomb
    2 months ago
    Eleven winters of moving boxes to higher ground, and this January the floor was bone dry through a week of steady rain. The crew laid plastic over everything, hauled the spoil out by bucket and swept up each evening. Marcus explained the cove joint problem in a way that finally made sense.
  • Ravi Chandrasekaran
    3 months ago
    Two other companies wanted to tear up my entire basement floor. These guys looked at it and said the water was coming through two cracks, injected both, and charged a fraction of what I was quoted elsewhere. Two wet seasons later, still dry. They diagnosed instead of selling.
  • Kathleen O’Ryan
    3 months ago
    The musty smell in our bedrooms is completely gone, that alone was worth it. Humidity went from 78% to 47%, the floors are noticeably warmer through the winter, and our PGE bill dropped. Honestly did not expect the energy difference.
  • Tomás Aguilar
    4 months ago
    Our kitchen floor had been bouncy for years and I assumed it was just an old house. Turned out three joists had rotted at the sill. They sistered them, set proper piers, and the floor is solid for the first time since we bought the place.
  • Bethany Kaur
    5 months ago
    Excellent work and the water intrusion is completely resolved. Only reason for four stars is scheduling slipped by about a week during the November rush, though they were upfront about it and knocked something off the invoice.
  • Gerald Pfeiffer
    5 months ago
    Called at 6am during an atmospheric river with water coming in. They had someone here before nine to look at it and did not gouge me on emergency pricing. The permanent fix went in the following week and I have not thought about the basement since.
  • Amara Nwosu
    6 months ago
    They did the structural work first and then sealed it, and explained exactly why that order mattered. Another company had quoted just the liner, over rotted joists. Glad I got a second opinion. The house sold without a single crawl space comment from the inspector.
  • Steven Halvorsen
    6 months ago
    They came out, spent forty minutes, and told me my problem was a downspout dumping straight against the foundation instead of into the drain line, a $40 fix I could do myself. Did not try to sell me a thing. When I do need real work done, there is no question who I am calling.
  • Lucia Bertolini
    7 months ago
    Ninety-year-old house that had never had anything done to it. They worked straight through January in the rain, which I did not think was even possible, and kept the site cleaner than I expected. Clear pricing and written moisture readings at the end.
  • Owen Fitzgerald
    2 weeks ago
    One corner of the house had been sinking for years and I kept putting it off. They found the cause during the inspection, explained push piers versus helical piers in a way I actually understood, and the door that never closed right now shuts like new. Wish I had called sooner.
Seal the ground, dry the house, drop the heating bill

How Crawl Space Encapsulation Protects Your Portland Home

Crawl space encapsulation seals the ground under your house so moisture stops entering the air you breathe upstairs. Bare soil gives off water all the time, and the stack effect (opens in a new tab) carries about 40% of that air into your ground floor rooms, the same path the EPA describes for indoor air quality (opens in a new tab).

Portland makes this worse in both directions. Warm summer air pulled through open foundation vents lands on cool surfaces and turns to water. Cold, wet winter air pulled through the same vents keeps every board under your floor damp for months, and wet fiberglass has already lost its R-value (opens in a new tab).

The ground under a Portland crawl space stays wet from October to May. Bare soil gives off water into the space all winter, which is why humidity readings under an unsealed floor here often sit above 70% for most of the year.

A 20-mil reinforced vapor barrier covers the floor and runs up the walls, sealed at every seam, pier and pipe. We air-seal and insulate the rim joists, then a dehumidifier holds relative humidity (opens in a new tab) under 55% through all 12 months. Where the framing above it has already softened, crawl space repair comes first, and the autumn walkthrough is how to tell.

  • We use a 20-mil reinforced liner, not thin 6-mil construction plastic
  • We seal the liner to the walls, piers and every pipe with butyl tape
  • We air-seal and insulate the rim joists to stop the stack effect
  • An ENERGY STAR rated dehumidifier holds humidity under 55% all year
  • We haul away old debris, fallen batts and vapor-damaged material
Crawl space wall inspected before encapsulation by Basement Waterproofing Portland
Self-Assessment

Signs You Need Crawl Space Encapsulation

These 5 signs tell you a Portland crawl space needs encapsulation. Four of them show up inside the house, so most owners never connect them to the space underneath.
  1. 1 A musty smell in bedrooms and hallways Your nose picks up mold growth long before your eyes do. That smell travels up from below through the stack effect.
  2. 2 Floors that stay cold all winter Bare rim joists and vented crawl spaces pull freezing air straight under your living space.
  3. 3 Insulation hanging down or lying in the dirt Fiberglass batts hold water, lose all R-value and become a mold substrate. They rarely stay up in a damp crawl space.
  4. 4 Condensation on ducts or pipes underneath Humid air meeting cool metal works the same way as a glass of ice water sweating. It drips onto everything below.
  5. 5 Supply lines that froze or burst in January An open foundation vent is the usual cause. Sealing the space fixes the pipe problem and the moisture problem at the same time.
The Ground Under Your House

Why Portland Crawl Spaces Get Damp

Portland’s Long Wet Season & Ground Moisture

Portland gets rain for about seven months of the year. Bare soil under a crawl space keeps giving off moisture the whole time, and that moisture has nowhere to go but up into the air under your floor.

Water Intrusion & Poor Drainage

Grading that slopes toward the house, or a downspout that empties too close to the foundation, sends rainwater straight under the crawl space. Once it gets in, there is often no drain to carry it back out.

Outside Air Entering Through Crawl Space Vents

Open foundation vents let humid summer air in to condense on cool surfaces. They also let cold, wet winter air sit under your floor for months. Either way, the vents feed the moisture problem instead of solving it.

How The Problem Gets Solved

What’s Included in Our Crawl Space Encapsulation System

Heavy-Duty Crawl Space Vapor Barrier

A 20-mil reinforced liner covers the floor, thick enough to survive a knee or a dropped tool. Six-mil construction plastic tears too easily to count as a real vapor barrier.

Sealed Foundation Walls, Piers & Penetrations

The liner runs up the walls and wraps every pier, taped and sealed at each seam and pipe. One unsealed edge turns the rest of the liner into decoration.

Crawl Space Vent Sealing

We seal foundation vents shut once the space is conditioned. An open vent undoes the rest of the system by feeding it outside air again.

Drainage & Sump Pump When Needed

Where the crawl space holds water, we add interior drainage and a sump pump before anything gets sealed. We never encapsulate over standing water.

Crawl Space Insulation

We air-seal and insulate the rim joists, closing the biggest air-leak path in most Portland homes and stopping cold floors above.

Humidity Control & Dehumidification

A dedicated, ENERGY STAR rated dehumidifier holds relative humidity under 55% year-round and drains on its own, so the space stays dry after the crew leaves.

Know The Difference

Crawl Space Encapsulation vs. Vapor Barrier: What’s the Difference?

A vapor barrier is one part of encapsulation, not the whole system. It is a plastic sheet laid over the dirt floor that blocks ground moisture from evaporating upward. On its own, it does nothing about the walls, the vents or the humidity already in the air.

Encapsulation seals the entire crawl space: the floor, the walls, every pier and pipe, the vents, and the air itself through a dehumidifier. A vapor barrier is only the first layer of that system. Laid down alone, it slows one problem while leaving the other three untouched.

Time Is Not On Your Side Here

Why Crawl Space Moisture Shouldn’t Be Ignored

Mold, Musty Odors & Moisture Problems

Relative humidity above 60% lets mold and mildew take hold on joists and subfloor. The smell reaches your bedrooms through the stack effect long before you see anything.

Wood Rot & Damaged Insulation

Steady moisture rots joist ends at the sill, which turns a sealing job into a structural one. Wet fiberglass insulation loses all its R-value and becomes part of the problem instead of solving it.

High Humidity & Poor Home Comfort

Damp air rising into the house means cold floors in winter and a heating system working harder than it should. Comfort and moisture come from the same place, so fixing one fixes the other.

Benefits of Crawl Space Encapsulation

  • Relative humidity held under 55% year-round, below the level mold needs to grow
  • Musty smell in the rooms above clears within days of the liner going down
  • Ground floor rooms measure 4 to 6°F (2 to 3°C) warmer through a Portland winter
  • Heating and cooling costs drop 10 to 18% once the space stops leaking conditioned air
  • Clean, lit, dry space you can actually store things in, backed by a 25-year liner warranty
Straight Numbers, No Guessing

Crawl Space Encapsulation Cost in Portland, OR

Crawl space encapsulation in Portland costs $5.75 to $8.50 per square foot ($61.90 to $91.50 per square meter), and most jobs finish in 2 to 4 days.

What Affects Crawl Space Encapsulation Cost?

  • Total square footage of the crawl space floor
  • Whether structural repair is needed before the liner goes down
  • Whether the space already has standing water or needs new drainage
  • Access, including crawl space height and how far materials have to be carried in

What’s Included in Your Estimate?

  • The 20-mil liner, sealed to walls, piers and every pipe
  • Rim joist air sealing and insulation
  • A dehumidifier sized for your square footage
  • Haul-away of old plastic, batts and debris

Free Crawl Space Inspection & Written Quote

The inspection that gives you a price is free. The proposal after it is a fixed price in writing, not an estimate that grows once the crew shows up. 0% financing runs for 18 months on any project.

Get My Free Written Estimate
How It Works

Our Crawl Space Encapsulation Process

Four steps sit between your first call and finished work. You will know what happens, who does it, what it costs and when it finishes before a single tool comes off the truck.

Step 1: Inspect, Clear & Prepare

We check the crawl space, then clear out old plastic, collapsed insulation and debris. We grade the floor smooth so the new liner lies flat against it.

Step 2: Correct Water & Drainage Problems

If the crawl space holds water, we solve that first, with drainage and a sump pump if needed. We never seal over an active leak.

Step 3: Install & Seal the Vapor Barrier

The 20-mil reinforced liner covers the floor and runs up the walls, fastened and taped at every seam, pier and pipe.

Step 4: Seal, Insulate & Control Humidity

We seal the vents, insulate the rim joists, and set a dedicated dehumidifier to hold humidity below 55% year-round, draining on its own.

32 Years Under Portland Homes

Why Portland Homeowners Trust Us

Choosing a contractor for crawl space encapsulation comes down to 2 questions: is the problem still solved in 10 years, and is the company that promised it still answering the phone. We have been answering since 1994. Portland homeowners pick us for 4 reasons, listed below.

Oregon CCB Licensed, Bonded & Insured

We carry an active Oregon contractor license, bond and insurance, so you can check us out before you let a crew into your basement. Since 1994 we have waterproofed 9,800 properties across the city of Portland.

Locally Owned & Operated

We are a Portland business, not a national franchise. We know this ground, from flood silt on the east side to hillside seepage above Burnside, because we have already dug into it.

No Subcontractors or High-Pressure Sales

Every technician is our own employee, background-checked and trained on our own systems. We test, measure and diagnose before we quote, and we cancel proposals regularly once the real fix turns out to be a downspout extension.

Transferable Warranty

Every system carries a lifetime warranty that covers labor and materials, not just parts. It transfers once to the next owner at no cost, which turns a wet-basement history into a selling point instead of a repair bill.

What Portland Homeowners Say About Us

4.9 out of 5 stars

  • Danielle Whitcomb
    2 months ago
    Eleven winters of moving boxes to higher ground, and this January the floor was bone dry through a week of steady rain. The crew laid plastic over everything, hauled the spoil out by bucket and swept up each evening. Marcus explained the cove joint problem in a way that finally made sense.
  • Ravi Chandrasekaran
    3 months ago
    Two other companies wanted to tear up my entire basement floor. These guys looked at it and said the water was coming through two cracks, injected both, and charged a fraction of what I was quoted elsewhere. Two wet seasons later, still dry. They diagnosed instead of selling.
  • Kathleen O’Ryan
    3 months ago
    The musty smell in our bedrooms is completely gone, that alone was worth it. Humidity went from 78% to 47%, the floors are noticeably warmer through the winter, and our PGE bill dropped. Honestly did not expect the energy difference.
  • Tomás Aguilar
    4 months ago
    Our kitchen floor had been bouncy for years and I assumed it was just an old house. Turned out three joists had rotted at the sill. They sistered them, set proper piers, and the floor is solid for the first time since we bought the place.
  • Bethany Kaur
    5 months ago
    Excellent work and the water intrusion is completely resolved. Only reason for four stars is scheduling slipped by about a week during the November rush, though they were upfront about it and knocked something off the invoice.
  • Gerald Pfeiffer
    5 months ago
    Called at 6am during an atmospheric river with water coming in. They had someone here before nine to look at it and did not gouge me on emergency pricing. The permanent fix went in the following week and I have not thought about the basement since.
Answers First

Frequently Asked Questions

Straight answers about cost, timing, warranty and what actually causes water in a Portland basement. Still unsure? Ask us directly, we would rather talk it through than have you guess.

Closed, in this climate, in both directions. In a Portland summer, an open vent pulls humid outside air onto cool surfaces where it turns to water. From October on, it dumps saturated air under your floor, holds the framing damp for seven months and drives up your heating bill. Sealed and conditioned outperforms vented in every test we run here.

A vapor barrier (opens in a new tab) is one layer of encapsulation, the plastic sheet over the dirt floor. Encapsulation adds sealed walls and pipes, vent sealing, insulation and a dehumidifier on top of it. A vapor barrier alone slows ground moisture. Encapsulation controls the whole space.

Yes. Sealing the ground stops new moisture from evaporating in, but it does not remove the moisture already trapped in the air and the framing. A dedicated dehumidifier (opens in a new tab) is what actually lowers humidity and keeps it there.

Yes, usually. About 40% of the air on your ground floor comes up from the crawl space, so sealing it typically shows up as a 10 to 18% drop in heating and cooling costs, plus floors that no longer feel cold in January.

Yes, and it is one of the more popular side effects. A clean, dry, lit crawl space becomes real storage instead of somewhere nobody wants to go.

Yes. That smell is the stack effect carrying crawl space air into your living space. Once the ground is sealed and humidity is under control, it clears within days, one of the few repairs people can actually smell working.

Not directly over it, no. We solve standing water first, usually with interior drainage and a sump pump, before any liner goes down. If the framing above it has already gone soft, that is crawl space repair first, and sealing over active water traps it exactly where you do not want it.

The 20-mil liner carries a 25-year material warranty, and the seals and workmanship are covered separately. The dehumidifier is the one mechanical part, and like any appliance it has a service life, which is why we check it during your free annual system service.

2 to 4 days for most homes, depending on square footage and whether structural repair is needed first.

Need Crawl Space Encapsulation? We Are Always Ready

Our crew is one call away. We know how stressful this gets, so we run 24/7 emergency dispatch across Portland and give you a fixed price before any work starts.

Call (877) 569-0306
Areas We Service

Covering Every Basement Across Portland

Basement Waterproofing Portland works inside the city limits only, covering 12 Portland neighborhoods and all 33 city ZIP codes. Soil changes from one street to the next here, so our crews work from what actually sits under each address rather than a single template.
Downtown Sellwood-Moreland Hawthorne Laurelhurst Alberta Arts St. Johns Multnomah Village Irvington Woodstock Montavilla Kenton Beaumont-Wilshire

Portland ZIP codes we cover

97201 97202 97203 97204 97205 97206 97208 97209 97210 97211 97212 97213 97214 97215 97216 97217 97218 97219 97220 97221 97222 97223 97224 97225 97227 97229 97230 97232 97233 97236 97239 97266 97267
Contact Us

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Water in the basement, a foundation crack you have been watching, or a crawl space nobody wants to open. Get a straight diagnosis from Basement Waterproofing Portland, with fast response, fixed pricing and workmanship guaranteed for life across the city of Portland.

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