i converted a 12x24 semi-attached garage into living space 6 years ago.
On the 'crete floor I had painted, then a layer of 4mil plastic, then
a layer of bluefoam insulation, then 3/4 particle board (used the blue
screws to secure the boards), then commercial carpet.

The carpet is moist and the room smells like a stagnant locker-room. I
ridge vented, but the trouble is (now) obviously that the concrete is
leeching ground-moisture upwards. So.. Ill take up the particle board
and do what?

I'd float the floor on 1x's but they'l rot.. Any Ideas?

Mike D

The main problem is the 4 mil plastic.

4 mil plastic will do little to stop moisture flow.

You generally need at least 2 layers of 6 mil plastic laid with all
seams taped or sealed even at the walls or foundation.


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i converted a 12x24 semi-attached garage into living space 6 years ago.
On the 'crete floor I had painted, then a layer of 4mil plastic, then
a layer of bluefoam insulation, then 3/4 particle board (used the blue
screws to secure the boards), then commercial carpet.

The carpet is moist and the room smells like a stagnant locker-room. I
ridge vented, but the trouble is (now) obviously that the concrete is
leeching ground-moisture upwards. So.. Ill take up the particle board
and do what?

I'd float the floor on 1x's but they'l rot.. Any Ideas?

Mike D

Make sure the entire slab is above grade. Water could be getting in through
the walls, sill plate, or migrating from the roof down the outside of the walls
and wicking through the mud sill. Put in a french drain.

Mike D wrote:
i converted a 12x24 semi-attached garage into living space 6 years
ago. On the 'crete floor I had painted, then a layer of 4mil plastic,
then a layer of bluefoam insulation, then 3/4 particle board (used
the blue screws to secure the boards), then commercial carpet.

The carpet is moist and the room smells like a stagnant locker-room. I
ridge vented, but the trouble is (now) obviously that the concrete is
leeching ground-moisture upwards. So.. Ill take up the particle board
and do what?

I'd float the floor on 1x's but they'l rot.. Any Ideas?

Mike D

Dirt is defiantly correct. Common concrete is not water proof. You may
need to lower the water table around the pad.

--
Joseph Meehan

26 + 6 = 1 It's Irish Math

On Wed, 23 Feb 2005 01:21:28 -0500, Mike D
wrote:

i converted a 12x24 semi-attached garage into living space 6 years ago.
On the 'crete floor I had painted, then a layer of 4mil plastic, then
a layer of bluefoam insulation, then 3/4 particle board (used the blue
screws to secure the boards), then commercial carpet.

The carpet is moist and the room smells like a stagnant locker-room. I
ridge vented, but the trouble is (now) obviously that the concrete is
leeching ground-moisture upwards. So.. Ill take up the particle board
and do what?

I'd float the floor on 1x's but they'l rot.. Any Ideas?

Mike D

The concrete isn't waterproof, but the 4-mil plastic ought to be,
and the foam, while not waterPROOF should be water resistant.
I'd look around for another source of water-intrusion before blaming
ground-water.

My instinct says that you ought to have put the plastic on
TOP of the blue foam, on the theory that the top edge is
warm and not likely to condense.

Goedjn Wrote:
On Wed, 23 Feb 2005 01:21:28 -0500, Mike D
wrote:

i converted a 12x24 semi-attached garage into living space 6 years
ago.
On the 'crete floor I had painted, then a layer of 4mil plastic, then
a layer of bluefoam insulation, then 3/4 particle board (used the
blue
screws to secure the boards), then commercial carpet.

The carpet is moist and the room smells like a stagnant locker-room.
I
ridge vented, but the trouble is (now) obviously that the concrete
is
leeching ground-moisture upwards. So.. Ill take up the particle board
and do what?

I'd float the floor on 1x's but they'l rot.. Any Ideas?

Mike D

The concrete isn't waterproof, but the 4-mil plastic ought to be,
and the foam, while not waterPROOF should be water resistant.
I'd look around for another source of water-intrusion before blaming
ground-water.

My instinct says that you ought to have put the plastic on
TOP of the blue foam, on the theory that the top edge is
warm and not likely to condense.


4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it readily
allows gaseous water to flow thru it.

6 mil plastic sheeting has a much lower perm rating and doubling the
sheets and taping the seams will eliminate most gaseous water.

The slab itself should be painted with a vapor barrier coating to
further eliminate any gaseous water entering the floor thru the porous
concrete slab.

The proper place for plastic sheeting is below the concrete in a living
space.

It is this gaseous water that will condense and cause mold and mildew
growth deapite liquid water entering from anywhere else.


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manhattan42 wrote:

4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it readily
allows gaseous water to flow thru it...

Then again,

http://www.hornerflooring.com/techgu...watervapor.pdf

says 4 mil polyethylene film passes 0.17 gr/h-ft^2 per "Hg of water vapor
pressure, vs 0.11 for 6 mil, vs about 20 (200X more) for 1/2" drywall.
A 1" hole in a sheet of drywall can pass a lot more water vapor.

A house with a 1000 ft^2 50 F wet basement floor with 70 F air at 50% RH
would have Pw = e^(17.863-9621/(460+50)) = 0.367 "Hg at the floor and Pa
= 0.5e^(17.863-9621/(460+70)) = 0.374 "Hg in the air, so moisture would
flow FROM the air TO the floor through a 4 mil poly film layer at a rate
of 1000(Pa-Pw)0.17 = 1.2 grains per hour, ie 1.2/7000 = 0.00017 pounds
per hour, ie about 1 drop of water every 2 weeks. Changing to 6 mil poly
would reduce this to about 1 drop every 3 weeks :-)

Nick

Wrote:
manhattan42 wrote:

4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it readily
allows gaseous water to flow thru it...

Then again,

http://www.hornerflooring.com/techgu...watervapor.pdf

says 4 mil polyethylene film passes 0.17 gr/h-ft^2 per "Hg of water
vapor
pressure, vs 0.11 for 6 mil, vs about 20 (200X more) for 1/2" drywall.
A 1" hole in a sheet of drywall can pass a lot more water vapor.

A house with a 1000 ft^2 50 F wet basement floor with 70 F air at 50%
RH
would have Pw = e^(17.863-9621/(460+50)) = 0.367 "Hg at the floor and
Pa
= 0.5e^(17.863-9621/(460+70)) = 0.374 "Hg in the air, so moisture
would
flow FROM the air TO the floor through a 4 mil poly film layer at a
rate
of 1000(Pa-Pw)0.17 = 1.2 grains per hour, ie 1.2/7000 = 0.00017 pounds
per hour, ie about 1 drop of water every 2 weeks. Changing to 6 mil
poly
would reduce this to about 1 drop every 3 weeks :-)

Nick

The problem with all the scientific rhetoric is that is does not take
into account the reality that gaseous water (humidty) passing up
through the concrete can be well more than 100% and that the
tempartures can drop well below freezing.

This adds up to temperatures and conditions well below the dew point
for that portion of air even at 70F or above.

The calculations above also fail to take into account that gases flow
from areas of high concentration to areas of low concentration
regardless of the air pressure.

This means that the natural progession of moisture will be up from and
through the concrete basement floor and into the living space above
where it will condense under most circumstances.

One thing you got correct, however, is that 4 mil poly is 3 times less
able to retard water vapor than 6 mil poly, and why it is not permitted
as a true vapor barrier by building codes.


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manhattan42 wrote:

4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it readily
allows gaseous water to flow thru it...

Then again,

http://www.hornerflooring.com/techgu...watervapor.pdf

says 4 mil polyethylene film passes 0.17 gr/h-ft^2 per "Hg of water
vapor pressure, vs 0.11 for 6 mil, vs about 20 (200X more) for 1/2" drywall.
A 1" hole in a sheet of drywall can pass a lot more water vapor.

A house with a 1000 ft^2 50 F wet basement floor with 70 F air at 50%
RH would have Pw = e^(17.863-9621/(460+50)) = 0.367 "Hg at the floor and
Pa = 0.5e^(17.863-9621/(460+70)) = 0.374 "Hg in the air, so moisture
would flow FROM the air TO the floor through a 4 mil poly film layer at a
rate of 1000(Pa-Pw)0.17 = 1.2 grains per hour, ie 1.2/7000 = 0.00017 pounds
per hour, ie about 1 drop of water every 2 weeks. Changing to 6 mil
poly would reduce this to about 1 drop every 3 weeks :-)

The problem with all the scientific rhetoric is that is does not take
into account the reality that gaseous water (humidty) passing up
through the concrete can be well more than 100% and that the
tempartures can drop well below freezing.

Humidty more than 100% and basement tempartures below freezing? :-)
It seems you can't even spell, much less appreciate science...

This adds up to temperatures and conditions well below the dew point
for that portion of air even at 70F or above.

Bull****. What HAVE you been smoking? :-)

The calculations above also fail to take into account that gases flow
from areas of high concentration to areas of low concentration
regardless of the air pressure.

No. Water vapor likes to flow from greater to lesser vapor pressures.

This means that the natural progession of moisture will be up from and
through the concrete basement floor and into the living space above
where it will condense under most circumstances.

Wrong wrong wrong again.

One thing you got correct, however, is that 4 mil poly is 3 times less
able to retard water vapor than 6 mil poly, and why it is not permitted
as a true vapor barrier by building codes.

Nope. It's only 0.17/0.11 = 1.5X less permeable.

Nick

Wrote:
manhattan42 wrote:

4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it
readily
allows gaseous water to flow thru it...

Then again,

http://www.hornerflooring.com/techgu...watervapor.pdf

says 4 mil polyethylene film passes 0.17 gr/h-ft^2 per "Hg of water
vapor pressure, vs 0.11 for 6 mil, vs about 20 (200X more) for 1/2"
drywall.
A 1" hole in a sheet of drywall can pass a lot more water vapor.

A house with a 1000 ft^2 50 F wet basement floor with 70 F air at
50%
RH would have Pw = e^(17.863-9621/(460+50)) = 0.367 "Hg at the floor
and
Pa = 0.5e^(17.863-9621/(460+70)) = 0.374 "Hg in the air, so
moisture
would flow FROM the air TO the floor through a 4 mil poly film layer
at a
rate of 1000(Pa-Pw)0.17 = 1.2 grains per hour, ie 1.2/7000 = 0.00017
pounds
per hour, ie about 1 drop of water every 2 weeks. Changing to 6 mil
poly would reduce this to about 1 drop every 3 weeks :-)

The problem with all the scientific rhetoric is that is does not take
into account the reality that gaseous water (humidty) passing up
through the concrete can be well more than 100% and that the
tempartures can drop well below freezing.

Humidty more than 100% and basement tempartures below freezing? :-)
It seems you can't even spell, much less appreciate science...

This adds up to temperatures and conditions well below the dew point
for that portion of air even at 70F or above.

Bull****. What HAVE you been smoking? :-)

The calculations above also fail to take into account that gases flow
from areas of high concentration to areas of low concentration
regardless of the air pressure.

No. Water vapor likes to flow from greater to lesser vapor pressures.

This means that the natural progession of moisture will be up from
and
through the concrete basement floor and into the living space above
where it will condense under most circumstances.

Wrong wrong wrong again.

One thing you got correct, however, is that 4 mil poly is 3 times
less
able to retard water vapor than 6 mil poly, and why it is not
permitted
as a true vapor barrier by building codes.

Nope. It's only 0.17/0.11 = 1.5X less permeable.

Nick


This isn't even worth a reply since what you have stated is NOT
science.

Diffusion is the method by which gases flow from areas of higher
concentration to areas of lower concentration regardless of pressure.
This is why gaseous water routinely enters basement spaces from the
ground below where it is more concentrated to the basement where it is
less so and often where the basement has a higher temperature and
pressure.

Dew points can be reached at temperatures in the 70s or higher
depending upon relative humdity of the air mass. For example, you can
get condensation forming when surface temperatures are at 73 degrees F
and the air temperature is 75 F with a 95% humidty.

There isn't much else to say except that perhaps you need to find
another major at Villanova if 'science' is yours........


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manhattan42 wrote:

4 mil plastic is "waterproof" but it is not "vaporproof"....4 mil
plastic has a relatively high perm rating which means that it
readily allows gaseous water to flow thru it...

Incorrect.

http://www.hornerflooring.com/techgu...watervapor.pdf

says 4 mil polyethylene film passes 0.17 gr/h-ft^2 per "Hg of water
vapor pressure, vs 0.11 for 6 mil, vs about 20 (200X more) for 1/2"
drywall...

A house with a 1000 ft^2 50 F wet basement floor with 70 F air at 50%
RH would have Pw = e^(17.863-9621/(460+50)) = 0.367 "Hg at the floor
and Pa = 0.5e^(17.863-9621/(460+70)) = 0.374 "Hg in the air, so moisture
would flow FROM the air TO the floor through a 4 mil poly film layer
at a rate of 1000(Pa-Pw)0.17 = 1.2 grains per hour, ie 1.2/7000 = 0.00017
pounds per hour, ie about 1 drop of water every 2 weeks. Changing to 6 mil
poly would reduce this to about 1 drop every 3 weeks :-)

We might compare this to Andersen's estimate that
an average family of 4 evaporates 2 gallons per day.

The problem with all the scientific rhetoric is that is does not take
into account the reality that gaseous water (humidty) passing up
through the concrete can be well more than 100% and that the
tempartures can drop well below freezing.

It takes all that into account. And RH can never exceed 100%, and basement
floor temps below freezing are extremely rare south of Alaska, and the last
two facts are irrelevant here. Just pointing out how utterly wrong you are,
again.

This adds up to temperatures and conditions well below the dew point
for that portion of air even at 70F or above.

How vague. Just what do you mean by this, exactly?

The calculations above also fail to take into account that gases flow
from areas of high concentration to areas of low concentration
regardless of the air pressure.

They flow because of vapor pressure vs air pressure differences. "Areas"
(vs volumes) with differing concentrations have different vapor pressures.

This means that the natural progession of moisture will be up from
and through the concrete basement floor and into the living space above
where it will condense under most circumstances.

Wrong wrong wrong again.

If the vapor pressure under the vapor barrier over the basement floor is less
than the vapor barrier in the room air (as above) water vapor will flow FROM
the room air TO the basement floor, through the resistance of the barrier, in
a miniscule fashion.

Diffusion is the method by which gases flow from areas of higher
concentration to areas of lower concentration regardless of pressure.

True, but again, vapor pressure and air pressure are different.

Dew points can be reached at temperatures in the 70s or higher
depending upon relative humdity of the air mass...

We might talk again after you learn to spell "humidity" :-)

Nick