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Concrete floor over dirt basement?



 
 
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  #1  
Old June 20th 10, 11:55 PM posted to alt.home.repair
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Posts: 6
Default Concrete floor over dirt basement?

Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. Do I need a vapor
barrier? Can I just pour right over the dirt? I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP
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  #2  
Old June 21st 10, 01:14 AM posted to alt.home.repair
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Posts: 1,640
Default Concrete floor over dirt basement?


"Jay Pique" wrote in message
...
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. Do I need a vapor
barrier? Can I just pour right over the dirt? I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP


Much depends on local conditions. The ideal is 4 to 6" of washed gravel
between the footings (the house does have footings doesn't it?) topped with
a vapor barrier then 4"+ of concrete. If there is ground water that makes
the dirt wet, even if it is only seasonal, the washed gravel helps prevent
it from wicking into the concrete along with the vapor barrier resulting in
a dryer basement. If you have moisture down there you may want to install
drainage pipes in the gravel to collect the water and channel it to a sump
pump, as a house that old will not have any exterior drainage around the
outside of the footings. Do it right you never will be sorry, do a cheap
inadequate job and you may have to do it over correctly to be happy..

  #3  
Old June 21st 10, 04:13 AM posted to alt.home.repair
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Posts: 149
Default Concrete floor over dirt basement?



"Jay Pique" wrote in message
...
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. Do I need a vapor
barrier? Can I just pour right over the dirt? I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP


The ideal would be crushed stone, a vapor barrier, and insulation
under the slab, but I can understand why you'd want to avoid the
effort involved in doing that.

For one thing, a house that old may not have the greatest footers. You
certainly don't want to undermine them excavating for the slab.

If' it's bone dry down there all the time you can probably get away
with putting down a good vapor barrier and pouring on top. But I'd
consult local experts familiar with the area and conditions.

One thing to keep in mind. Wet concrete throws off a *lot* of water
vapor while it is setting and drying out. It has no place to go but
up. In an unfinished house it's not a problem, but you're going to
want to provide positive ventilation to get rid of all the moisture or
you'll be asking for mold issues.

Have you checked for radon? Now would be the time to plan for
remediation if you have a radon problem, and that will almost
certainly required gravel under the slab so the space can be
depressurized and exhausted externally. That's usually the first step
in remediation.

Good luck with your big project!

Paul F.
  #4  
Old June 21st 10, 04:20 AM posted to alt.home.repair
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Posts: 5,158
Default Concrete floor over dirt basement?

Jay Pique wrote:
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. Do I need a vapor
barrier? Can I just pour right over the dirt? I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP

Call your friendly local concrete flatwork company and get an estimate.
Unless house is tiny, too much concrete to hand-mix or with a rental
mixer, unless you pour it as multiple slabs. Need to make sure there is
drainage before you do anything. 1890 house will not have outside
foundation drains, so you will likely need gravel and a sump pit. Also a
good time to replace any interior posts with modern ones with proper
footers, and do any needed floor leveling. Are you SURE about ceiling
height? Just because you don't bang your head, does it meet local code
to be counted as living space? And is there an outside entry to get the
concrete down there? Carrying it down in buckets sucks.

This will not be a cheap project. It is worth the money to get on-site
professional advice, and probably have a pro do most of the work.
Floating concrete is not as easy as it looks. You also want a pro
inspection of the mortar/chinking on the stone foundation. 1890s mortar
loves to turn to dust without warning if there is a heavy rain.

If cost is an issue, and basement is basically dry, lots of vintage
house owners put a brick or paver floor down instead of concrete. Much
easier for a DIY, since you can do a few feet at a time. And if it ever
floods, easy to take up to do any repair on drains and such.

--
aem sends...
  #5  
Old June 21st 10, 03:09 PM posted to alt.home.repair
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Posts: 165
Default Concrete floor over dirt basement?

On Jun 20, 6:55*pm, Jay Pique wrote:
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. *There's sufficient ceiling height for a 4" slab without
excavating, which I'd definitely prefer not to do. *Do I need a vapor
barrier? *Can I just pour right over the dirt? *I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP


JP

Before you pour, or have poured, your new floor consider installing an
interior ground ring for your electrical system. While you are
putting in your drainage system you dig the trench around the
periphery a foot deeper and put a bare number two copper conductor
around the edge. You make sure that it is long enough to come up out
of the pour through a nonmetallic conduit at the point immediately
beneath the service disconnecting means / customer service unit of
your electrical system. It needs to be long enough to go all the way
to the neutral buss bar of the service equipment. Were the end
overlaps the tail to the service equipment you install a split bolt
connector to bond the two runs of the ground ring to itself. You then
back fill the trench to the installation depth of your drainage
piping. Connect that ground ring to the same buss bar were the
neutral conductor from the utility's transformer is terminated. This
will provide your electrical system with a far better grounding
electrode system than anything else you are likely to have on the site
unless you are served by an entirely metallic underground water
utility supply that is free of plastic pipe or exterior coatings.
Such a grounding electrode system will make your homes electrical
system much more resistant to surge and spike damage. It is
especially worth doing if your electrical system has only driven rod
electrodes. If you install a surge arrester a good earth ground will
make it much more effective. It will never be as easy to install a
good grounding electrode system as it is during this work. It's your
home so it may be worth doing it right while it is easy to do.
--
Tom Horne, Electrician
  #6  
Old June 21st 10, 03:16 PM posted to alt.home.repair
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Posts: 1,582
Default Concrete floor over dirt basement?

On Jun 20, 6:55*pm, Jay Pique wrote:
Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. *There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. *Do I need a vapor
barrier? *Can I just pour right over the dirt? *I'm just starting to
do my research, so any thoughts or info would be appreciated.

JP


You really ought to have some gravel and a vapor barrier. But exactly
what you need to do and perhaps can get away without depends on the
historical conditions in the basement. If you're in arizona and the
basement ground has been desicated hard earth for the past 100 years
you can just pour some concrete on top. If you're in the SE and the
basement soil is still suitable for crops if you added some lights
then you need the gravel and vapor barrier.
  #7  
Old June 21st 10, 09:47 PM posted to alt.home.repair
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Posts: 6
Default Concrete floor over dirt basement?

On Jun 21, 10:16*am, jamesgangnc wrote:
On Jun 20, 6:55*pm, Jay Pique wrote:

Just bought an 1890 two-story brick house with a stone foundation.
The basement is dirt right now, and I'd like to pour a concrete slab
down there. *There's sufficient cieling height for a 4" slab without
excavating, which I'd definitely prefer not to do. *Do I need a vapor
barrier? *Can I just pour right over the dirt? *I'm just starting to
do my research, so any thoughts or info would be appreciated.


JP


You really ought to have some gravel and a vapor barrier. *But exactly
what you need to do and perhaps can get away without depends on the
historical conditions in the basement. *If you're in arizona and the
basement ground has been desicated hard earth for the past 100 years
you can just pour some concrete on top. *If you're in the SE and the
basement soil is still suitable for crops if you added some lights
then you need the gravel and vapor barrier.


Thanks for all the replies. I'm continuing to research and will likely
post back with more questions. Given that this is a real fixer-upper
I'm definitely going to be hanging out here a bit I'm sure.

JP
  #8  
Old July 24th 10, 03:51 PM posted to alt.home.repair
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Posts: 6
Default Celotex for expansion joints?

Regarding the use of expansion joints in the basement, I priced out
the "actual" stuff at around 40 cents a lineal foot for the 1/2"x4"
stuff. Then I got to thinking that Celotex is only $8.40 per SHEET
which will get me 88 feet, so only about a dime a foot. My question
is, will this do the same job as the real stuff? Thanks.
JP
  #9  
Old July 24th 10, 04:39 PM posted to alt.home.repair
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Posts: 2,030
Default Celotex for expansion joints?


"Jay Pique" wrote in message
...
Regarding the use of expansion joints in the basement, I priced out
the "actual" stuff at around 40 cents a lineal foot for the 1/2"x4"
stuff. Then I got to thinking that Celotex is only $8.40 per SHEET
which will get me 88 feet, so only about a dime a foot. My question
is, will this do the same job as the real stuff? Thanks.
JP


May be OK indoors, but outdoors it would deteriorate fast from the weather.
Anything that allows movement will work. Indoors, there is little thermal
variation over the course of a year so anything may do the job, including
nothing. Variation indoors may be 30 degrees over the year while outdoors
it can be 100+ along with freezing water in joints.

  #10  
Old July 24th 10, 05:01 PM posted to alt.home.repair
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Posts: 6
Default Celotex for expansion joints?

On Jul 24, 11:39*am, "Ed Pawlowski" wrote:
"Jay Pique" wrote in message

...

Regarding the use of expansion joints in the basement, I priced out
the "actual" stuff at around 40 cents a lineal foot for the 1/2"x4"
stuff. *Then I got to thinking that Celotex is only $8.40 per SHEET
which will get me 88 feet, so only about a dime a foot. *My question
is, will this do the same job as the real stuff? Thanks.
JP


May be OK indoors, but outdoors it would deteriorate fast from the weather.

 




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