Caulking basement wall to slab seam

Posted by hobbes on June 11, 2007, 6:58 am

Hi,

I detected some Radon exposure in my basement and am trying to seal it
up to stop the Radon gas seeping in.

I have a concrete basement, walls and slab floor. What I am trying to
seal up is the gap between the slab-floor and the concrete walls. The
gap's width is about 1/16th to 1/4 of a inch and varies depending on
where you look in the basement.

This is probablly a dump question but what is the best way to plug
that gap? I tried using SikaFlex SL (Self Leveling) concrete caulk.
But it just seems to pour into a bottomless void. I guess it must be
the crush rock beneath the slab. I thought I would use this because I
think if would give me the best air tight seal.

Questions:

1) Am I using the wrong Caulk? I.E. Should I be using a non self
leveling one. That way it would not drip into that bottomless pit. Any
caulk recomendations

2) Foam backing rod. Could not find one thin enough, so ended up using
window foam insulation. This does work, but it takes ages to slip into
that crack and I have like 300 feet perimiter to do.

3) Should I be trying to fill the crack with some concrete first? If
so is that a bad idea because you want some give in your basement to
allow for thermal expansion etc.

4) How would a professional Radon company seal a basment? Can I
replicate what they would do? i.e. am I doing this all wrong?

Thank you for your kind help.

Warmest regards, Mike.

Posted by ransley on June 11, 2007, 7:43 am

> Hi,
> I detected some Radon exposure in my basement and am trying to seal it
> up to stop the Radon gas seeping in.
> I have a concrete basement, walls and slab floor. What I am trying to
> seal up is the gap between the slab-floor and the concrete walls. The
> gap's width is about 1/16th to 1/4 of a inch and varies depending on
> where you look in the basement.
> This is probablly a dump question but what is the best way to plug
> that gap? I tried using SikaFlex SL (Self Leveling) concrete caulk.
> But it just seems to pour into a bottomless void. I guess it must be
> the crush rock beneath the slab. I thought I would use this because I
> think if would give me the best air tight seal.
> Questions:
> 1) Am I using the wrong Caulk? I.E. Should I be using a non self
> leveling one. That way it would not drip into that bottomless pit. Any
> caulk recomendations
> 2) Foam backing rod. Could not find one thin enough, so ended up using
> window foam insulation. This does work, but it takes ages to slip into
> that crack and I have like 300 feet perimiter to do.
> 3) Should I be trying to fill the crack with some concrete first? If
> so is that a bad idea because you want some give in your basement to
> allow for thermal expansion etc.
> 4) How would a professional Radon company seal a basment? Can I
> replicate what they would do? i.e. am I doing this all wrong?
> Thank you for your kind help.
> Warmest regards, Mike.

I would fill it with mortar mix.

Posted by hallerb@aol.com on June 11, 2007, 8:07 am

> > Hi,
> > I detected some Radon exposure in my basement and am trying to seal it
> > up to stop the Radon gas seeping in.
> > I have a concrete basement, walls and slab floor. What I am trying to
> > seal up is the gap between the slab-floor and the concrete walls. The
> > gap's width is about 1/16th to 1/4 of a inch and varies depending on
> > where you look in the basement.
> > This is probablly a dump question but what is the best way to plug
> > that gap? I tried using SikaFlex SL (Self Leveling) concrete caulk.
> > But it just seems to pour into a bottomless void. I guess it must be
> > the crush rock beneath the slab. I thought I would use this because I
> > think if would give me the best air tight seal.
> > Questions:
> > 1) Am I using the wrong Caulk? I.E. Should I be using a non self
> > leveling one. That way it would not drip into that bottomless pit. Any
> > caulk recomendations
> > 2) Foam backing rod. Could not find one thin enough, so ended up using
> > window foam insulation. This does work, but it takes ages to slip into
> > that crack and I have like 300 feet perimiter to do.
> > 3) Should I be trying to fill the crack with some concrete first? If
> > so is that a bad idea because you want some give in your basement to
> > allow for thermal expansion etc.
> > 4) How would a professional Radon company seal a basment? Can I
> > replicate what they would do? i.e. am I doing this all wrong?
> > Thank you for your kind help.
> > Warmest regards, Mike.

> I would fill it with mortar mix.- Hide quoted text -
> - Show quoted text -

mortar mix then caulking..... mrtar mix prevents caulking from falling
in.

caulk the sills on all walls even interior ones. and any floor
openings like bolts or boards bolted to floor.

you preping the home for sale? this usually comes up then.

radon mitigation companies seal everything then install a exhaust
system
'
how high was your number

Posted by hobbes on June 11, 2007, 8:29 am

> > > Hi,
> > > I detected some Radon exposure in my basement and am trying to seal it
> > > up to stop the Radon gas seeping in.
> > > I have a concrete basement, walls and slab floor. What I am trying to
> > > seal up is the gap between the slab-floor and the concrete walls. The
> > > gap's width is about 1/16th to 1/4 of a inch and varies depending on
> > > where you look in the basement.
> > > This is probablly a dump question but what is the best way to plug
> > > that gap? I tried using SikaFlex SL (Self Leveling) concrete caulk.
> > > But it just seems to pour into a bottomless void. I guess it must be
> > > the crush rock beneath the slab. I thought I would use this because I
> > > think if would give me the best air tight seal.
> > > Questions:
> > > 1) Am I using the wrong Caulk? I.E. Should I be using a non self
> > > leveling one. That way it would not drip into that bottomless pit. Any
> > > caulk recomendations
> > > 2) Foam backing rod. Could not find one thin enough, so ended up using
> > > window foam insulation. This does work, but it takes ages to slip into
> > > that crack and I have like 300 feet perimiter to do.
> > > 3) Should I be trying to fill the crack with some concrete first? If
> > > so is that a bad idea because you want some give in your basement to
> > > allow for thermal expansion etc.
> > > 4) How would a professional Radon company seal a basment? Can I
> > > replicate what they would do? i.e. am I doing this all wrong?
> > > Thank you for your kind help.
> > > Warmest regards, Mike.

> > I would fill it with mortar mix.- Hide quoted text -
> > - Show quoted text -

> mortar mix then caulking..... mrtar mix prevents caulking from falling
> in.
> caulk the sills on all walls even interior ones. and any floor
> openings like bolts or boards bolted to floor.
> you preping the home for sale? this usually comes up then.
> radon mitigation companies seal everything then install a exhaust
> system
> '
> how high was your number- Hide quoted text -
> - Show quoted text -

I am not selling. But the state (NY) had this DIY test offer for 7$US
for any NY resident. So I thought I would check and see. My living
space was 1.2 PiC/l and the basement was 10.8 PiC/l.

Best, Mike.

Posted by hallerb@aol.com on June 11, 2007, 10:34 am

> > > > Hi,
> > > > I detected some Radon exposure in my basement and am trying to seal it
> > > > up to stop the Radon gas seeping in.
> > > > I have a concrete basement, walls and slab floor. What I am trying to
> > > > seal up is the gap between the slab-floor and the concrete walls. The
> > > > gap's width is about 1/16th to 1/4 of a inch and varies depending on
> > > > where you look in the basement.
> > > > This is probablly a dump question but what is the best way to plug
> > > > that gap? I tried using SikaFlex SL (Self Leveling) concrete caulk.
> > > > But it just seems to pour into a bottomless void. I guess it must be
> > > > the crush rock beneath the slab. I thought I would use this because I
> > > > think if would give me the best air tight seal.
> > > > Questions:
> > > > 1) Am I using the wrong Caulk? I.E. Should I be using a non self
> > > > leveling one. That way it would not drip into that bottomless pit. Any
> > > > caulk recomendations
> > > > 2) Foam backing rod. Could not find one thin enough, so ended up using
> > > > window foam insulation. This does work, but it takes ages to slip into
> > > > that crack and I have like 300 feet perimiter to do.
> > > > 3) Should I be trying to fill the crack with some concrete first? If
> > > > so is that a bad idea because you want some give in your basement to
> > > > allow for thermal expansion etc.
> > > > 4) How would a professional Radon company seal a basment? Can I
> > > > replicate what they would do? i.e. am I doing this all wrong?
> > > > Thank you for your kind help.
> > > > Warmest regards, Mike.
> > > I would fill it with mortar mix.- Hide quoted text -
> > > - Show quoted text -

> > mortar mix then caulking..... mrtar mix prevents caulking from falling
> > in.
> > caulk the sills on all walls even interior ones. and any floor
> > openings like bolts or boards bolted to floor.
> > you preping the home for sale? this usually comes up then.
> > radon mitigation companies seal everything then install a exhaust
> > system
> > '
> > how high was your number- Hide quoted text -
> > - Show quoted text -

> I am not selling. But the state (NY) had this DIY test offer for 7$US
> for any NY resident. So I thought I would check and see. My living
> space was 1.2 PiC/l and the basement was 10.8 PiC/l.
> Best, Mike.- Hide quoted text -
> - Show quoted text -

yeah thats high. do you have any basement ventilation? a friend had
numbers like that, added a computer muffin fan to a extra dryer
exhaust vent he wasnt using.

end of problem he said fan used about a buck a year of electric, he
left a small entrance vent so air could flow easily.

i would definetely get it fixed somehow.

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