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3/2/2020
1
Addressing Radon in the Home
Dick Kornbluth
(315)391‐6886
Better Buildings: Better BusinessWisconsin Conference
March 9-10, 2020
What This Session Covers
• Part 1:Intoduction to radon– What it is
– Where its found
– How it’s measured
– The health risks of exposure to radon
• Part 2:Mechanisms of radon entry
• Part 3: A survey of radon entry routes
• Part 4: Sealing procedures
Part 1About Radon
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What is Radon?
•Gas
•Colorless
•Odorless
•Tasteless
•Chemically inert
•Radioactive
• Radioactive half-life = 3.8 days
Where it Comes From
• Generated by the natural, spontaneous radioactive decay of Uranium
• Found where there are deposits of uranium in specific rock formations:– Mostly shales, limestones and granites
Radon Measurement Units
• In the United States, radon levels are measured in pico curies per liter (pCi/l) which is a measurement of radiation
• According to the EPA, the average outdoor level of radon is 0.4 pCi/l
• Average indoor level is 1.3 pCi/l
• Radon should be mitigated if average indoor level is 4 pCi/l or greater
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EPA Radon Map
Zone 1 = >4 pCi/l
Zone 2 = 2-4 pCi/l
Zone 3 = < 2 pCi/l
What Does Radon Do?
Long time exposure to radon is considered to be the second leading environmental cause of lung cancer after cigarette smoking
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Health Risks from Radon Exposure
Source: EPA’s A Citizen’s Guide to Radon
Radioactive Half‐Life
• Time it takes for one‐half of a given amount of a radioactive element to transform into another radioactive element
– For Uranium = 4.5 billion years
– For Radon =3.8 days
Uranium 2lb
Radon 1 lb
4.5 billion yrs
Uranium 1lb
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Radon Measurement Units
• Radon – pCi/l
• Pico curies/liter of air in US
• Progeny – WL – Working Level
• Working level – For residential applications = pCi/l x .5
• Used for measuring worker exposure in certain industries
Testing Radon
• Testing for Radon in Air• Short‐Term Tests – 2‐90 days ‐ Integrated
• Charcoal test kit – most common– Provides single overall average radon level over test period
– Must be sent to lab for analysis
– Cost: $15‐$30/kit
• Liquid Scintillation
• Electronic Monitors – Provides hourly radon levels and/or average radon level over test period
• E‐perm– Electret Ion Chamber
• Long‐term Tests – 90 days to 1 year• Alpha track – most common
• Electronic Monitors
• E‐perm
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– Long‐term Tests – 30 days to 1 year
• Alpha‐Track– Provides single overall average radon level over test period
– Must be sent to lab for analysis
• Testing for Radon in Water
– Only applies to well water
Type of Test Short‐term Long‐term DIY
Charcoal 2‐7 Days Yes
Liquid scintillation 2‐7 days Yes
E‐Perm – electret ion chamber
2‐90 days 91‐360 days No
Continuous radon monitor (CRM)
2‐90 days 91‐360 days Yes/No
Alpha‐track 30‐90 days 91‐360 days Yes
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Short‐Term Radon Testing Devices
Charcoal Test Kit
Charcoal Test KitEperm Test
Continuous Radon Monitor
Liquid Scintillation
Alpha-track
DIY Continuous Radon MonitorsDon’t do hourly readings
Airthings CorentiumHome $179-$199
Safety Siren Pro $149.99
Radon in Water
• Radon gas is less soluble in hot water than in cold water
• Known health risk from water‐borne radon is due to radon released into air and breathed in as a result of:
– Cooking
– Showering
– Clothes and dish washing
• Approx 10,000 pCi/l in water = 1 pCi/l in air
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• EPA has proposed to require community water suppliers to provide water with radon levels no higher than 4,000 pCi/L, which contributes about 0.4 pCi/L of radon to the air in your home.
• Easily tested
Short‐Term Tests
• EPA Protocols– Real Estate Transaction related
• Test in lowest level of house suitable for living space– E.g. Modern house with unfinished basement which could be converted to living space
– Don’t test in crawlspaces
– Don’t test in basements not suitable for living space
» E.g. 19th century house with dirt floor basement with less than 6’ in head room
– Not real estate transaction related• Test in lowest level of house used for living space
Short‐Term Test ProtocolFor CC, LS and CRM for 2‐7 dys
• House must be in “winter” condition
– All windows closed at least 12 hrs before test starts
– All windows closed during test
– All exterior doors closed except for normal going out and coming in for 12 hrs before test and during test
• Test must be kept away from sources of heat, moisture and moving air during test
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Can’t measure radon with a single point reading
• Radon levels fluctuate constantly in any building
• All the factors that can change the pressure in a house will affect interior radon levels:– Exhaust fan operation
– Wind
– HVAC operation
– Barometric pressure changes
– Rain
– Outside temperature changes
– Stack effect
Actual Continuous Radon Monitor Traces
Avg23.1pCi/l
3.1 pCi/l
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Alpha Track Test
Alpha‐Track• Can do short‐term (30‐90 dys) or long‐term (90 dys‐1 yr)
• No special living condition requirements– Windows don’t have to be kept closed (Test period is 1 mo to 1 yr!)
– Test not affected by moisture or humidity
• Detector must be sent away to manufacturer for analysis
• Results reported as average radon level over test period
Part 1 Summary
• Radon: colorless, odorless, tasteless, chemically inert, radioactive gas
• Generated by spontaneous decay of Uranium
• Found in deposits of shale, limestone and granite
• Uranium half‐life = 4 billion yrs
• Radon half‐life = 3.8 days
• Second leading cause of lung cancer after cigarette smoking
• Radon is easily measured in buildings with either short‐term or long‐term tests
– Short‐term tests = 2‐30 days
– Long‐term tests = 31 days – 1 year
• Need closed house conditions for short‐term tests, unless doing 30‐day test
• Karst geology makes reliable testing difficult
• According to the EPA, Radon action level is 4 pCi/l
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Part 2Mechanisms of Radon Transport
Into Buildings
What Determines Radon Level in Building?
Uranium
Source Strength
Soil Porosity
Radon Soil Concentrations and Transport Mechanisms
• Radon level in a house is influenced by two factors in the soil:
– Its source concentration – Uranium
–How easily it moves through the soil• Soil particle size: gravel loam sand clay
• Soil moisture content: dry wet
• Dry, gravelly soil Radon moves more quickly
• Wet, clay soil Radon moves more slowly
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Radon Transport into Buildings
Radon levels in a building fluctuate continually. There are many factors influencing rate of radon transport into building:
General Mechanisms of Radon Transport
• Diffusion
• Pressure driven flow
• Radon in water
Diffusion
• Relatively slow process
– Not major mechanism for radon entry
– Concrete is porous, so diffusion accounts for some radon entry
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Radon Entry is a Pressure‐Driven Flow
Environmental Factors
• Barometric pressure
• Rain
• Wind
Barometric Pressure Effects
• Small
• Radon levels in soil increase as barometric pressure decreases
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Rain Effects
• Temporary
• Rain spike – as soil becomes saturated radon levels in building increase
Wind Effect
Building System Factors
• Stack Effect
• Mechanical ventilation
• Duct leakage
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Stack Effect
Stack Effect
• Can be complex interaction
• Air sealing reduces exfiltration at top and infiltration at bottom
– Less radon coming in
• But air sealing reduces natural ventilation, building tighter
– Radon levels can increase
Mitigating RadonSub‐Slab Depressurization
In-Line Fan
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Non‐Heating Season Stack Effect
Effect of opening up second floor window at 9:30pm
Window opening effect – Stack
Effects of Mechanical Ventilation
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RETURN LEAK EFFECTS
SUPPLYRETURN
Basement
1ST Floor
Chimney
Radon and House TightnessNo correlation established between indoor radon levels and building tightness
Data from studies in the 1990’s showed a scatter plot when radon levels were plotted against building air leakage measurements
But that’s a different question than the one that asks “What happens to radon levels when we increase building tightness?”
Oak Ridge IAQ Study2010‐2011
• Effect of weatherization on radon levels inconclusive:
– Some houses, radon increases
– Some houses, radon decreases
– Some houses, radon stays the same
• Can be issue with measuring techniques and weather‐related effects
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Radon in Water
Radon in Water
• Source: Wells, can be individual or community
• Health risk is not from drinking; it’s from breathing radon released into the air when water is heated: showering, cooking, washing
Radon in Water
• Water/Air equivalent:
– 10,000 pCi/l in water = 1 pCi/l in air
• Testing for radon in water
– Test kits are available
• Radon in water problems can be fixed with plumbing aeration systems that release radon before it gets into house
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Part 2 Summary
• Soil factors that influence rate of radon entry into buildings
– Concentration of uranium in ground
– Porosity and wetness of soil
• Dry, gravelly soil – radon moves more easily
• Wet, clay soil – radon moves more slowly
• Diffusion vs pressure‐driven flow
• Environmental factors
– Barometric pressure
– Rain
– Wind
• Building system factors
– Stack effect
– Mechanical effect
– Duct leakage
• Radon in water
Part 3: Radon Entry Points
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Radon Entry Points
Locations of Radon Entry in Slab
Radon
Floor cracksPerimeter drain
Sump
Floor/wall joint
Floor penetrations
Wall penetrations
Block wall core
Floor drain
Crawlspaces
Crawlspace
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Block Wall Core
Radon
Block wall core
Rubble Stone Walls
• Can be source of radon
• Difficult to determine if wall is source
• Can do short term radon test called Flux Test
– 2‐day exposure sufficient
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Charcoal test kit
Radon Flux Test
Floor Cracks
Radon
Floor cracks
Floor Cracks
Cracks come in different sizes!
Large
Medium
Hairline
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Expansion joints
Can floor crack sealing eliminate radon entry?
Diameter of Radon atom = .000000008 inches
Diameter of human hair = .0030 inches
Diameter of hairline crack = .003 inches
Hairline crack = 375,000 x diameter of Radon atom
No, but you can reduce rate of radon entry into the living space
Floor and Wall Penetrations
Radon
Floor penetrations
Wall penetrations
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Floor and Wall Penetrations
Floor Drains
Radon
Floor drain
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Floor Drains• Floor drains are a sub‐set of floor penetrations.
• They can be connected to the ground (A) or connected to the waste system (B)
A B
Radon entry for sure
No radon entry if no leaks in pipe
Floor Drains
Condensate Drains
• For condensate lines from furnaces and central air conditioners
• Can empty into floor drains and sumps, but sometimes just a hole in the floor.
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French (perimeter) Drains
Radon
Perimeter drain
French (perimeter) Drains
• Most commonly installed as part of a water management system
• Frequently associated with a sub‐slab drain tile system and sump pump
• Occasionally connected to a drain to daylight, with no sump
Drain tile
Open French (perimeter) Drain
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Drain to Daylight
French Drain with Weep Holes in Block
Weep hole
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French Drain Covered by Framing
French Drain Behind Framing
Floor/Wall Joint
Radon
Floor/wall joint
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Floor/Wall Joint
• Can be as narrow as a floor crack and as wide as a French (perimeter) drain
– Some builders have installed the slab as a “floating slab” not anchored to the foundation walls
– If there is a water management system there will be either a sump or a gravity drain to daylight. There may even be a sump with no pump and with a drain to daylight.
Sumps
• Can be part of a water management system
• Consists of a:
– sump pit
– sump basin or liner
– sump pump to remove water
– check or backflow prevention valve to prevent water from coming back into the sump basin
– discharge line to deliver the water to the exterior of the building
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https://home.howstuffworks.com/home-improvement/plumbing/sump-pump1.htm
Sump Pumps
• Two Types:
– Submersible – totally contained in the basin
– Pedestal – pump motor housed in a shaft that extends above the basin
Submersible pump Pedestal pump
How the Sump Pump Works
• All sump pumps have a float switch
• As the water in the basin rises to a certain level, the float rises and triggers the pump to remove the water
Float and rod move
Untethered Float Vertical Float –rides on rigid rod
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Sump Basins
• Most commonly plastic prefabricated
But Sump Pits Can be Any Hole
Are All Sump Pits Connected to the Ground?
No, if used for gray water from washing machines
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If a sump pit is connected to the ground, it must be sealed!
Crawlspaces
Crawlspace
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Crawlspaces
• Major entry point for radon
• Can be accessible or inaccessible
• Can be used for storage and/or required for access or not – sealing strategy will differ
Other Holes
Part 3 Summary
Radon entry points
• Block walls – not always
• Rubble stone walls – not always
• Floor cracks
• Floor/Wall penetrations
• Floor drains
• Condensate drains
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• French (perimeter) drains
• Floor/wall joint
• Sumps
• Crawlspaces
• Other holes
Part 4 – Sealing Procedures
Goals
• All accessible soil gas entry points are sealed using appropriate sealing materials and methods
• There is no entry of soil gases into basement or living space (slab on grade) from the holes that are sealed
• Work is done in compliance with nationally recognized radon mitigation industry standards
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National Radon Mitigation Standards
There are two standards which govern the radon mitigation industry:
An ASTM standard:
And an American Association of Radon Scientists and Technologists standard:
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Radon Reduction Procedures
• Procedures divided into 2 groups
– Basic procedures
• Should be done on every house
• Reasonable cost to do in terms of labor and materials
– Advanced procedures – Shown in red
• Should be done if time and budget permits
• I will cover basic procedures first, then talk about Advanced Procedures
Basic Procedures
• Block wall core sealing
• Rubble stone wall sealing
• Floor crack sealing
• Drain sealing
– Floor drains
– Condensate drains
• Wall penetration sealing
• Floor penetration sealing
• Floor/wall joints
– Accessible floor/wall joints
– Floor/wall joints behind finished walls
• Framing over joint
• Joint behind framing
• French drains
– Accessible French drains
– French drains with weep holes
– French drain behind finished walls
• Framing over drain
• Drain behind framing
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• Other holes
– Holes in concrete slab
– Holes under bathtubs
– Holes under furnaces
Basic Procedures
Block wall cores
• Can use communication test to check for block wall connection to ground
• Connection to soil usually not an issue for exterior block walls due to waterproofing
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May be an issue for interior block walls
Living spaceGarageCrawlspace
Internal kneewall –no waterproofing
Waterproofing
Sealing block wall cores
Stuff w fiberglass and fill with mortar
Fill w spray polyurethane foam
QA: No smoke enters block wall core when shop vac is on
Spray foam
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Fiberglass
Mortar
Rigid foam boardCaulk
Rubble Stone Walls
• Sealing is problematic
• Research indicates that rubble walls need to allow moisture migration through wall to maintain structural integrity if lime‐based mortar used
• If sealing, necessary to maintain drainage plane
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Membrane
Floor drainage
Sealing Rubble Stone Walls
Floor Cracks
• For cracks less than ½” width, seal with urethane gunnable caulk
• For cracks ½” wide or greater, insert backer rod in crack and then seal with gunnable or self‐leveling urethane caulk– Polyethylene Backer rod
• Include expansion joints
Recommended Types of Urethane caulk Type NP‐1 = Gunnable non‐saggingType SL ‐1 = Self‐leveling (best for wide cracks)
Floor Crack Sealing
Floor Crack
Expansion Joint
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Floor/Wall Penetrations
• For joints less than ½”, seal with NP‐1 caulk
• For joints between ½” and 1”, plug with backer rod and then seal with NP‐1 caulk
• For joints greater than 1”, seal with spray foam insulation
• QA: No smoke enters joint when shop vac is on
Floor Drains
• Floor Drains
• Condensate drains
• QA: When drain top is temporarily sealed with duct tape, no smoke enters joint with floor when shop vac is on
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Retrofit One Way Drains
Dranjer FR-2
Good for drains 2” to 8” diameter
From instruction sheet
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Condensate Drains
• If condensate drain is a floor drain, replace with a one‐way drain, which allows water to enter but prevents soil gases from coming into basement or living space (for slab on grade houses)
One-way Drain
• If condensate line is inserted into a hole in the slab, seal the line in the hole with caulk.
• Use silicone caulk which will allow line to be removed from drain
QA: For regular drains, see floor drain aboveFor drilled hole in floor, no smoke enters drain
when shop vac is on
Make sure there is a trap in the condensate line to prevent soil gases from entering the room.
The trap should have at least 3” of water on each side
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French (perimeter) Drains
• Necessary to seal drains without interfering with their water processing function
Drain tile
French Drain Procedure
• Cut backer rod to fit tightly into top half of French drain channel leaving at least 1/2 “ of space between top of backer rod and floor
• If filling with mortar, fill remaining channel with mortar
• If filling with SL‐1 self‐leveling caulk, make sure that there are no gaps between the backer rod and the sides of the channel
• If there are, fill them with NP‐1 caulk first
Backer rod installed
Backer rod
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French drain sealed
French Drain with Weep Holes or Drainage Channels
• When sealing French drain, need to incorporate weep holes or drainage channels into seal
• One option is to use a heavy duty membrane to cover both the drain and the weep hole
– Polyethylene sheeting, 10 mil thick or greater
– 45 mil EPDM roofing
• Secure to wall and to floor with NP‐1 caulk and reinforce with pressure‐treated 1”x2” secured with mechanical fasteners.
• If there is evidence of water entry through the wall, extend membrane above the water entry point
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Floor/Wall Joint
Floor/Wall joint
Floor/Wall Joint
• For joints less than ½”, seal with NP‐1 caulk
• For joints between ½” and 1”, plug with backer rod and then seal with NP‐1 caulk
• For joints greater than 1” plug with backer rod and fill with mortar or SL‐1 caulk
• QA: No smoke enters joint when shop vac is on
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Floor/Wall Joint
Narrow joint Wide joint
Backer rod
Sump Sealing
• First determine if sump pit is connected to the ground; yes, if
– the bottom of the pit is open to the ground and not concrete
– There are drain tile openings in the basin
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Concrete sump w concrete floor
Concrete sump w dirt floor
Sump pit with drain tile Sump pit with drain tile
Sump Cover Installation
• Submersible pumps
– Cover can be fabricated or purchased commercially
– Cover must be material that is rigid and water resistant
• 1/4 polycarbonate sheet – Lexan, e.g.
• 1/2” or greater pressure‐treated plywood
• Cover should be cut to fit inside top of basin
• Install a one‐way drain in the cover
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Sump Sealing
• Cut holes for any piping that must penetrate the cover
• Put a notch in one of the holes for the power cord
• Disconnect the piping from the sump
• Run a bead of silicone caulk around the edge of the sump basin
• Install the sump cover
Sealed Submersible Pumps
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Sealed Submersible Pumps
Pedestal Pumps
• Cannot use flat cover because motor for pump sits on rigid stalk and cannot be disassembled.
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Two Options
• Replace pedestal pump with submersible pump
– Install sump pump with equal or greater horse power to the pedestal pump.
• Install a commercially obtainable HiRise cover
HiRise Cover
Special case: Backup Systems
• Some sumps have electrical or water‐drivennsump backup systems.
• Difficult to install flat cover
• Can use HiRise cover
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Crawlspace sealingNational Radon Mitigation Standards
• Membrane for sealing crawlspaces must be a minimum of 3‐mil cross‐laminated polyethylene sheeting or 6‐mil polyethylene sheeting
• Heavier gauge sheeting (10‐mil or thicker) must be used if crawlspace is used for storage or accessed for
maintenance
• The membrane must be sealed around all posts
– Conflicts with NREL SWS’s which do not allow wood posts below membrane
• Membrane must be sealed to foundation walls with NP‐1 caulk as long as walls are flat
– Can use spray polyurethane foam for irregular surfaces such as rubble stone walls
• All penetrations through the membrane must be sealed
• All joints in the membrane must be lapped at least 12”
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• If heavier membrane is used, reinforce attachment to foundation wall and posts with 1”x2” pressure‐treated furring strips, caulked in place.
• Install floor drain in lowest part of crawlspace
• Install sump pit and sump pump if water entry is an issue
– Note: If evidence on foundation walls of water entry, secure membrane to foundation walls above this point.
Install one way drain in crawlspace membrane
PT PlywoodMembrane
For standard membranes For heavier membranes
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Rubble Stone Walls
Before
After
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Other Holes
• Any hole through the slab should be sealed with appropriate material, e.g. concrete.
Fill with concrete Cover with Lexan
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