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Self-leveling concrete? Options
#1 Posted : Wednesday, December 23, 2009 11:44:33 PM
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You know Street,you asked  at the right time because I remember a renovation job my dad's company did years and years ago where we could not use plastic as a slab vapor barrier either.What we did was use tar paper under a gravel base.He said that thats what they used to use long before sheet plastic arrived on the building scene.It's the 'bituminous coating' that you see in old drawings of old transformer vaults and such.We laid the tarpaper down on the dirt then set a 2" layer of gravel(or rough sand or hard pack with no stones.) reinfocing wire then the concrete.

#2 Posted : Thursday, December 24, 2009 12:38:00 AM
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Dang davisonH, that sounds like a lot of work.  That must've been back when men were men!  

I was hoping to level the dirt, dump X-number of yards of liquid into the crawlspace, come back tomorrow and have a hard, flat floor that I can use a creeper on to get around.  Then I could insulate and water-proof and encapsulate old mold and life would be rosy from here on out.

I'm into easy...I think I need one of those Easy buttons from Staples.


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#3 Posted : Friday, December 25, 2009 2:50:05 AM
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Pat Miketinac
#4 Posted : Friday, December 25, 2009 3:24:37 AM
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Interesting idea, Street. Think about putting down an inch or two of extruded polystyrene (based on your ground temperature) before pouring the concrete. That way, condensation on the concrete is unlikely and you can take advantage of it's thermal mass to stabilize your house temp., since you plan to use the space as a plenum.

Rob Roy discusses slab insulation in his recent book, "Earth Sheltered Houses", available from M.E N. or his website, cordwoodmasonry.com. It's a great book for any D.I.Y construction, with resources.

My 22 year old earth shelter is based on his first design, but I only used 6 mil Visquene under the slab and outside the walls because the ground temp. here in Florida is 72 deg., keeping the house near that temp. year round.

John Stiles
#5 Posted : Friday, December 25, 2009 11:15:23 PM
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Ken Kern had a cement and burlap floor idea. It's been years but the basic idea was work up the dirt then drive some 3"  holes for pilings then fill with cement lay down a layer of burlap and plaster or pour an inch or two of cement over it. After the ground settles there is an air gap for insulation.

In 1976 we did a hippie floor here in upstate NY in the house where I live . We used a pool cement mix on bare ground. In some places it's pretty thin an inch or two but it has held. There are different grades of concrete.

None of these ideas allow for a creeper unless it has all terrain tires.
Maybe just the tires and forget the concrete.

Now the water vapor is a very different part of the issue. Our floors sweat like crazy in the summer no matter if they are under laid with plastic or not. To insulate from the ground temp is the best way to minimize condensation.

Hydrological issues are complex. To treat the air with fans and dehumidifiers has worked best for us. In retrospect a fully plastic and insulation under laid floor with a troweled finish of colored concrete would have saved a lot of consternation. But we were broke.

#6 Posted : Saturday, December 26, 2009 4:08:18 PM
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Pat, I would put down some form of insulation - maybe the fan-fold type of polystyrene?

I think our ground temp stays around 58 degrees or so. With average annual precip at 12", it also stays fairly dry.


So far my homemade "yurt" has withstood a 3 inch rain, a 2" rain, winds in excess of 50mph for six hours, and six inches of wet snow.  Since I have access to a natural gas well, I have rigged-up a central heating system to stay warm.  The temp has gotten down to the teens several times, but my yurt stays about 60.

I rebuilt some of the structural support under the house, rebuilt a pad for the chimney, built an exterior closet for mechanical use, run gas lines for appliances, have all of the sub-floor plumbing replaced, and torn out some interior walls.  I'm half-way thru getting the new subfloor down.  

My natural gas has no odorant added (nor did I want to add any), so I was very reluctant to pipe the gas into my crawlspace and/or house.  And since most-all black pipe is imported now, I have no confidence that the pipe will not fail and start leaking.  I compromised by running 1/2" steel gas lines inside a 1" PVC "conduit".  Once I have this system finished, a gas leak will either be vented outdoors via the conduit, or will set off a detector under the appliance.  I think I can sleep with this arrangement.

The most interesting thing I have learned is about insurance companies:  my bank places a 13-day hold on all insurance checks.  I have received 4 separate checks from the insurance company on this one claim.  I am not able to live in my house while the work is progressing, so I am claiming "Additional Living Expenses" as part of the claim.

My additional living expense allowance has a dollar-amount limit.  So in effect, I am consuming a significant portion of this limit (about $90 per day) just waiting for the insurance company's checks to clear.  This really irritates me - I am planning to complain to the state insurance commission if the insurance company does not make this right by me.

My helpers are here - gotta go.


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#7 Posted : Saturday, December 26, 2009 4:08:18 PM
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Hello again,


I am wondering if it would be feasible to try to pour self-leveling concrete over the dirt floor in my crawlspace.  I have about 1800 square feet that I would like to cover.  My goal would be to block water vapor at ground level, then convert the crawlspace into a large (return-air) plenum.  I really really really do not want to try to cover the dirt with plastic.

I've never worked with this type of concrete and am wondering what the pour size limits might be.
After I had this poured, I would water-proof the (crawlspace) concrete walls and floor and then insulate all of it.

My wife and I are very adversely affected by mold, and I cannot see any way to avoid mold if I have a vapor barrier anywhere at the subfloor level - looks to me as though there will always be condensation on the warm side of any vapor barrier I install.  I think I'd rather just allow the vapor to pass thru and not try to block it - that way it won't condense.

Any thoughts or comments would be appreciated.


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