Results 1 to 19 of 19
  1. #1
    Join Date
    Jun 2008
    Location
    Maryland
    Posts
    1,049

    Default radon mitigation

    Consider a house with sloped lot. The lot is sloped front to rear. At the front, the grade is just below the 1st floor level. The grade slopes to the rear where there's a walk out sliding door on the back of the house.

    The front 1/2 is on a crawl space that is closer to grade. The rear half is a basement with a concrete salb. The crawl space floor on the front half is 4-5 feet above the level of the slab of the rear 1/2.

    When mitigating radon in a house like this, would you do the crawl first, or the the sub slab first? I understand its possible that both might be needed but if you were going to do one first, which would be more effective?

    Similar Threads:
    2018 ASHI InspectionWorld

  2. #2
    Join Date
    Mar 2007
    Location
    Succasunna NJ
    Posts
    574

    Default Re: radon mitigation

    I would do the basement first.
    If the crawlspace is vented, the air exchange will help reduce radon build-up. In the basement, the radon is already in the house.

    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

  3. #3
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: radon mitigation

    Basement first, but most likely both will need to be done. What was the pCi/L reading?

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  4. #4
    Join Date
    Jun 2008
    Location
    Maryland
    Posts
    1,049

    Default Re: radon mitigation

    The house in question is a family members. We've had one of my 1027's over there for extended periods in the past. Highs in the basement were in the 19's for short term averages. 1st floor erratic depending on conditions such as open or closed house conditions. The reading spike significantly during bad weather, mainly rain.

    We're running a long term test with an alpha track now.


  5. #5
    Join Date
    Mar 2007
    Location
    Spring Hill (Nashville), TN
    Posts
    5,847

    Default Re: radon mitigation

    Quote Originally Posted by John Dirks Jr View Post
    The house in question is a family members. We've had one of my 1027's over there for extended periods in the past. Highs in the basement were in the 19's for short term averages. 1st floor erratic depending on conditions such as open or closed house conditions. The reading spike significantly during bad weather, mainly rain.
    That is normal during bad weather, rain, snow , etc....

    We're running a long term test with an alpha track now.
    That will give you the best reading.

    Scott Patterson, ACI
    Spring Hill, TN
    www.traceinspections.com

  6. #6
    Paul Ybarra's Avatar
    Paul Ybarra Guest

    Default Re: radon mitigation

    Is the crawlspace concrete, gravel or dirt? Is the basement walls poured concrete of block walls? Do you have sump pit anywhere? + more questions.

    Normally a mitigator will treat both area's (required here in IL) unless you can justify why it is not done. Justification is a radon diagnostic test which can be with a short term radon tests (both need to be < 4.0 pCI/L come one in basement and one above the crawl) and pressure extension readings with a micro manometer. In every proposal we require our design to be followed to warranty our service. Out designs treat all areas.
    If a customer insists to treat only one area at a time the price goes up because we are wasting more time ... Time is money..

    Just my 2 cents


  7. #7
    Join Date
    Mar 2007
    Location
    Succasunna NJ
    Posts
    574

    Default Re: radon mitigation

    And it really may not be that hard to do both. It all depends if you can put the basement radon pipe close to the crawlspace, all you would then need is some extra pipe and a 'Y'.

    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

  8. #8
    Join Date
    Mar 2007
    Location
    Cape Cod, Massachusetts
    Posts
    574

    Default Re: radon mitigation

    Darren,

    If the basement and crawl have common air space you will need to do both.

    If they are totally separate you can do the area that you took the reading in first, but I suspect you'll need to do both areas. Besides, you would want to get the long term average below 2.0 as recommended by EPA.


  9. #9
    Join Date
    Jun 2008
    Location
    Maryland
    Posts
    1,049

    Default Re: radon mitigation

    Quote Originally Posted by Paul Ybarra View Post
    Is the crawlspace concrete, gravel or dirt? Is the basement walls poured concrete of block walls? Do you have sump pit anywhere? + more questions.

    Normally a mitigator will treat both area's (required here in IL) unless you can justify why it is not done. Justification is a radon diagnostic test which can be with a short term radon tests (both need to be < 4.0 pCI/L come one in basement and one above the crawl) and pressure extension readings with a micro manometer. In every proposal we require our design to be followed to warranty our service. Out designs treat all areas.
    If a customer insists to treat only one area at a time the price goes up because we are wasting more time ... Time is money..

    Just my 2 cents
    Crawl is dirt with a plastic barrier that has openings that need sealing. Poured concrete basement walls. No sump pit.


  10. #10
    Join Date
    Mar 2007
    Location
    Succasunna NJ
    Posts
    574

    Default Re: radon mitigation

    John,

    Are there ducts running through the crawl?
    Sealing all the duct joints in a crawlspace with the probability of radon is a requirement here in NJ.

    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

  11. #11
    Join Date
    Mar 2007
    Location
    Colorado Springs, CO
    Posts
    1,217

    Default Re: radon mitigation

    Quote Originally Posted by Darren Miller View Post
    Are there ducts running through the crawl?
    Sealing all the duct joints in a crawlspace with the probability of radon is a requirement here in NJ.
    Are you also required to seal duct joints in a basement with a probability of radon?

    "Baseball is like church. Many attend but few understand." Leo Durocher
    Bruce Breedlove
    www.avaloninspection.com

  12. #12
    Join Date
    Jun 2008
    Location
    Maryland
    Posts
    1,049

    Default Re: radon mitigation

    Quote Originally Posted by Darren Miller View Post
    John,

    Are there ducts running through the crawl?
    Sealing all the duct joints in a crawlspace with the probability of radon is a requirement here in NJ.
    Yeah, ducts are in the crawl. At the following page from my site, that's me checking out one of them in the very crawl that we're discussing.

    Maryland-Home-Inspectors-Licensed-Annapolis-Baltimore-Anne Arundel-Prince Georges


  13. #13
    Join Date
    Mar 2007
    Location
    Succasunna NJ
    Posts
    574

    Default Re: radon mitigation

    Quote Originally Posted by Bruce Breedlove View Post
    Are you also required to seal duct joints in a basement with a probability of radon?
    No. Here's what it says:

    9) Any ductwork that is routed through a crawlspace or beneath a slab shall be properly taped or sealed.

    Darren www.aboutthehouseinspections.com
    'Whizzing & pasting & pooting through the day (Ronnie helping Kenny helping burn his poots away!) (FZ)

  14. #14
    Join Date
    Dec 2008
    Location
    Maryland
    Posts
    2,778

    Default Re: radon mitigation

    John,
    Since the crawl space is dirt with plastic is it ventilated? If so, what type?
    You say it has opening that need sealing. Are they partial sealed now?
    What were the readings in the crawl space?


  15. #15
    Join Date
    Mar 2008
    Location
    Rocky Mountains of Boulder, CO
    Posts
    158

    Default Re: radon mitigation

    Quote Originally Posted by John Dirks Jr View Post
    Crawl is dirt with a plastic barrier that has openings that need sealing. Poured concrete basement walls. No sump pit.
    John,
    I installed radon mitigation systems for many years (back in the 90's). Based upon experience, the crawlspace is the source.

    We'd seal it up with thick mil plastic and create a sub-membrane depressurization system. Liquid Nails on the foundation perimeter and at seams and penetrations. We credit that work towards a full system if needed after testing just that crawlspace seal. Just sealing the crawlspace will affect the Rn levels tremendously, but will not likely get it down to 'safe.' So before sealing the crawlspace over, we'd install branched perforated PVC, and pipe a penetration up through the plastic and cap it for future. Now if you stick a fan on that crawlspace system, that would probably take care of the entire house. The low pressure on the crawl will draw a ton.

    A sub-membrane depressurization system for a crawlspace is the most effective method.

    But just to make it legit, pop a hole in the basement floor too. Connect that basement point to the crawlspace system and blow it out.

    Crawlspaces are actually an ideal thing for mitigators, because it's typical THE source. We typically love hitting the crawlspace first, because it's highly effective and working the crawlspace is cosmetically appealing to the homeowner (who was likely trying to sell the property and keep things pretty.)

    For inspecting radon mitigation systems, I wrote a Standards of Practice for Inspecting Radon Mitigation Systems International Standards of Practice for Inspecting Commercial Properties - InterNACHI

    Hope that helps.

    Last edited by Benjamin Gromicko; 12-10-2010 at 09:48 AM.

  16. #16
    Join Date
    Nov 2009
    Location
    Winston-Salem, NC
    Posts
    89

    Default Re: radon mitigation

    I would do the slab. If that takes care of it fine if not I would install a Temp Vent fan in the crawl space. If that didn't do it I would then place the barrier in the crawl and hook into the system.


  17. #17
    Join Date
    Mar 2009
    Location
    Winfield, IL
    Posts
    37

    Default Re: radon mitigation

    I do radon testing in Chicago and suburbs and I cannot remember ever performing a post mitigation radon test on a house where the both basement and crawl were not mitigated as a unit. Can't imagine there are any real savings by choosing to mitigate one foundation type over another.

    Last edited by Eric Williams; 12-10-2010 at 09:56 AM. Reason: typo

  18. #18
    Join Date
    Mar 2007
    Location
    Anacortes, Washington
    Posts
    395

    Default Re: radon mitigation

    John,

    I agree with Ben and this can be a "do it yourself" project for the family member. I would add some PVC drain pipes (depending on size) under the vapor barrier, seal the barrier seams and attach to foundation walls. Add your fan system and then re-test. Most likely this will bring the readings under 4.0


    //Rick


    Lopez Home Inspections; San Juan Island Home Inspections By Pacific Crest Inspections
    Orcas Village and East Sound Home Inspections; Orcas Island Home Inspections By Pacific Crest Inspections

    Rick Bunzel
    WWW.PacCrestInspections.com
    360-588-6956

  19. #19
    Join Date
    Jun 2008
    Location
    Maryland
    Posts
    1,049

    Default Re: radon mitigation

    Since the possibility is that both will be needed and the crawl portion is more DIY friendly, we'll have the contractor install a sub slab de-pressurization for the basement. He'll be installing a capped T in the up pipe so we can tie in a sub membrane from the crawl if needed.

    Thanks everyone for your input. I'll keep you posted on the proceedings.


Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •