A sealed liner and dry air under the house
Crawl space encapsulation in Tigard
Encapsulation separates your house from the ground it sits on. Done in the right order it ends the damp smell and keeps the floor framing dry. Done over standing water it hides a problem.
Why the space under a Tigard house gets damp
Bare soil gives off moisture all year. In the rainy months the ground under the house is wet even when no water is visible, and the air above it is close to saturated.
Foundation vents were meant to carry that moisture away. On a mild, wet day they bring in air that is already damp, and it leaves its moisture on the coolest surfaces it finds: ducts, pipes and the underside of the floor.
The first signs are indoors. A musty smell after the heating comes on, cupped floorboards, or insulation that has dropped from between the joists.
What an encapsulated crawl space has in it
The parts, and what to check on each
The liner
Thick reinforced plastic, far heavier than the thin black sheet builders lay. Ask for the thickness in writing and whether it is rated for foot traffic.
Seams and edges
Every overlap is taped and the top edge is fastened and sealed to the wall. Loose edges are how damp air gets back in.
Piers and pipes
Each pier is wrapped and taped. Pipes and wires that pass through the liner are sealed around.
Vents and the hatch
Vents are closed from inside and the access hatch gets a gasket. A space that is sealed on the ground but open at the vents is only half done.
Drying the air
A crawl space dehumidifier, or a small supply of heated air from the house. It needs a power outlet and a drain for the water it collects.
Wall insulation
Often the old insulation between the joists comes down and rigid board goes on the walls instead. Ask which approach is proposed and why.
The order matters more than the product
Find and stop liquid water
If water stands under the house after rain, drainage and usually a pump come first. Crawl space repair covers that stage.
Clear out
Old plastic, fallen insulation, wood scraps and debris are removed. Sharp stones are raked level so they do not puncture the new sheet.
Deal with damaged wood
Framing is checked with a moisture meter. Anything decayed is dealt with before it is sealed in.
Lay, seal and close
Liner down and up the walls, seams taped, piers wrapped, vents shut.
Dry and measure
The dehumidifier goes in with a humidity gauge you can read without crawling inside.
Things to settle before the liner goes down
Closing the vents changes how the crawl space is ventilated under the building code. Ask how the design meets Oregon's residential code and whether the work needs a permit from the city.
A sealed liner covers the soil that a pest inspector normally looks at. Ask whether a strip at the top of the wall is left clear for inspection.
Gas appliances that draw air from the crawl space, and any radon system, have to be allowed for. Tell the company what is down there.
Questions that sort a careful bid from a quick one
- What humidity will the space be held at, and how will I see the reading?
- Where does the dehumidifier drain, and who services it?
- What did the moisture meter read on my joists and beams?
- If water appears on top of the liner next winter, what is the plan?
Encapsulation questions
Is a vapor barrier the same as encapsulation?
No. A vapor barrier is a sheet laid loose over the soil. Encapsulation seals that sheet to the walls and piers, closes the vents and dries the air.
Can I store things on the liner?
Light, clean items on a liner rated for it, yes. Ask the company, because sharp or heavy objects can puncture thinner sheets.
How long does the work take?
It depends on the size of the house, the headroom and how much has to be cleared out first. The company can tell you once it has been under the house.
Damp smell coming up through the floor?
Call and say what you found under the house. The company will tell you whether it needs drainage, a liner or both.
Get a waterproofing company on the phone
For homeowners with water coming into a basement or crawl space, or a yard that drains toward the house.
Call (503) 555-0120Calls can be recorded. Read how the referral is paid for and what happens to your details.