Hello,

I have heard different opinions on the use of gravel along with a poly
6mil vapor barrier. I am trying to conclude what the best solution is
to control the moisture in my crawl.

Here is what im working with:

1950's Cape Cod, Brick, 5' crawl (approx 1200sq feet). The ground is
mostly soft dirt, mostly dry but the furnace is down there on blocks
approx 2-3 feet off the ground, so its been running alot this winter
and we just bought the house. There is a sump pump that is located in
the crawl.

I have purchased 6mil Poly sheets to cover the crawl but have not
installed yet.

My question is will just the poly sheets be enough to keep moisture
down and prevent mold, or do I need to put some kind of stone either
under or over the poly?

If so what size stone, how much (thick) etc... OR will it even help
much one or the other...

Any suggestions or expierence is appriciated!


Jason

have you had water problems in this crawl space? mold, rotting joists,
standing water, etc?

Jason wrote:
Hello,

I have heard different opinions on the use of gravel along with a poly
6mil vapor barrier. I am trying to conclude what the best solution is
to control the moisture in my crawl.

Here is what im working with:

1950's Cape Cod, Brick, 5' crawl (approx 1200sq feet). The ground is
mostly soft dirt, mostly dry but the furnace is down there on blocks
approx 2-3 feet off the ground, so its been running alot this winter
and we just bought the house. There is a sump pump that is located in
the crawl.

I have purchased 6mil Poly sheets to cover the crawl but have not
installed yet.

My question is will just the poly sheets be enough to keep moisture
down and prevent mold, or do I need to put some kind of stone either
under or over the poly?

If so what size stone, how much (thick) etc... OR will it even help
much one or the other...

Any suggestions or expierence is appriciated!


Jason

Generally I would suggest stone under the poly to allow any water to
have a way to move UNDER it. I certainly would use the poly if it were my
home.

However different local conditions and different construction situations
may call for different solutions.


--
Joseph Meehan

Dia duit

Look at the Building Science Corporation web site.
That has some useful - researched - info on sealed crawl spaces.
lo
To be of any use, the poly must be lapped and sealed and sealed to the
surrounding foundation. If, as marson suggests, there is moisture, look
at ways of keeping it out of the crawl space or removing it. If there
is extra info - say existing rot or moisture - let us know.
TB

Andy replies:

Here's what I did to a pier and beam house in Texas.

1) I put down black poly plastic over the dirt in the entire
crawlspace. I did NOT seal or tape. This was to provide
a vapor barrier, not a hermetic seal..

2) The house had NO foundation vents. I put in a bunch
spaced about 15 feet apart around the perimeter. In this
manner the moisture from the earth would condense on
the underside of the plastic. What leaked up was easily
ventilated out by the foundation vents....

As a result, when I sold the house 20 years later, the floor
joists were in NEW condition, with no damage whatsoever.

The ventilation is the key. The purpose of the plastic is
to limit the rate at which moisture in the ground can get into
the air.

I hope this helps. It ain't hard to do.. And not expensive.
It is , however a thankless, dirty job.... :))))

Andy in Eureka, Texas

Just overlap the poly a few inches. You're trying to cut down the
moisture, not remove it totally. Forget rocks unless you need a few
on top to keep the poly from flapping. Better ventilation is good too.

Just lay out the poly and see what happens, If you need to do more,
then do it after you see how the simplest solution works.

Jason wrote:
Hello,

I have heard different opinions on the use of gravel along with a poly
6mil vapor barrier. I am trying to conclude what the best solution is
to control the moisture in my crawl.

Here is what im working with:

1950's Cape Cod, Brick, 5' crawl (approx 1200sq feet). The ground is
mostly soft dirt, mostly dry but the furnace is down there on blocks
approx 2-3 feet off the ground, so its been running alot this winter
and we just bought the house. There is a sump pump that is located in
the crawl.

I have purchased 6mil Poly sheets to cover the crawl but have not
installed yet.

My question is will just the poly sheets be enough to keep moisture
down and prevent mold, or do I need to put some kind of stone either
under or over the poly?

If so what size stone, how much (thick) etc... OR will it even help
much one or the other...

Any suggestions or expierence is appriciated!


Jason

The joists are not rotting, but I have had standing water for a time
when the old pump quit working, also along one wall there is almost
what looks like a trench about 1 foot deeper than the rest of the dirt
floor and it has water in it, im not sure if this has eroded (sp?) over
the years or its part of the under ground drainage that goes into the
sump pump hole. Most of the ground is dry but certain parts are damp
and mushy