concrete pad for drying

[Gary_C]

I have always believed that putting a vapor barrier under a concrete slab was a total waste of vapor barrier.  Concrete is absolutely NOT porous or it could not be used for swimming pools and water dams. You could not get water through intact concrete with a high pressure pump.

The water that appears on the surface of concrete slabs is actually condensation that forms because the concrete is below the dew point temperature of the air.  When you set something on a concrete slab and there is moisture under the item, it is because you have insulated that spot and it is colder than the surrounding concrete.

Save your vapor barrier for other uses.

[FeltzE]

Well then we must agree to disagree, 

In many places you will find building code requires a vapor barrier under concrete in structures. Concrete in pools and basements require a coating such as "Dry-Lock" a commercial concrete sealer used on both home basement walls, and pool interiors.

In areas with high water tables like Florida and Lousiana there are other issues to contend with, however in the stony state of Maryland, I would be concerned with drainage. High clay volume and stony soil may create an issue with waste water disposal forcing a high rate of evaporation rather than drainage.

Furby I've got to agree with you that the septic field should be green space if at all possible and that building atop of it should be only a last option.  Considering the compaction issue, again you should compact the soil to code prior to building and depending on where you build, you may have to  dig your footers to below the designated frost line. But for this purpose you could build a "floating slab" without any additional compaction of the surface, essentially you build your form boards to the slab size digging only enough to develop your desired sill thickness tapering the interior bottom of the slab from thinnest in the center to the thickest at the sill in a parabolic curve. By forming the bottom in a slight curve arching more steeply at the sill you reduce the stress points, create a strong sill where the slab takes a pounding and avert compaction issues by minimizing the disturbance of already setteled dirt (assuming there is no fill required).... it's a technique I've seen work in both western New York and her in North Carolina. The final slab is free of connection to the building structure allowing for frost heave or settling. The key is to ensure that the building is framed seperately to the slab. This can work well for a pole barn or shed but is not suitable for a home structure.

Even if you have good drainage I would spend the $10-$20 on putting down 4 -6 mill plastic sheeting as a barrier. Don't use a "home wrap" product like Tyvek because they will wick moisture to some degree and are designed to reduce airflow through the structure.

I must quantify my certification for these comments, I am a graduate of ....
School of hard knocks.
Beer hall of fame awardee
Certified S@@t House Lawer
Brown Belt in Office Debate


Eric

[Ga_Boy]

I must quantify my certification for these comments, I am a graduate of ....
School of hard knocks.
Beer hall of fame awardee
Certified S@@t House Lawer
Brown Belt in Office Debate


Eric

Eric,


Now that is funny!!   My sides is killing me!!!





Mark

Qualified Sea Lawyer

[FeltzE]

Thanks Mark,

Always can use some Navy support, I'm sure that after you get down here to visit you will tell the awful truth of my operation to the FF members. ... That is I'm also homeless, and only wish I had a sawmill...

Eric

[Dan_Shade]

I'm gonna move the location, my ground has a lot of clay, and probably barely perced as it is, the grass is definately greener there, that's how I figured out where the drainfield is located.

I went to enjinearin school, but i've long forgotten all of that stuff!

I too am a brown belt in office debate, in fact i'm so good at it, I sometimes find myself arguing against my original point!

[Gary_C]

No need to disagree with me, just stating my opinion. If you wish to follow the code and bury plastic or your money, go right ahead. Nowdays it's less trouble than burning. No one should know for a long time.

The reason they coat pool walls is the chlorine in the water will attack the cement and some of the aggregate in the concrete. Also basement floors need sealer because they usually pour a "basement mix" that has so much water in it that it can be poured in one corner and it will level itself. That concrete tends to flake and you can constantly sweep up powder so it needs to be sealed.

Just MHO     

[wiam]

If you have been inside of a hydro-electric dam you would realize that concrete was porous.  Water just runs in through the walls.  Kind of freaky with 80 feet of water on the other side.

Will

[Gary_B]

  Dan,
   Sounds like you have a bit of a problem there, being a native of Southern Maryland and as strict as the building codes are now days, I think you had better find another spot for that concrete slab, no doubt about it you sure dont want to build it over a leech bed or anything to do with a septic system. And second of course as soon as the concrete truck pulls up to your place in Lexington Park , the neighbors will be calling Leonardtown, and the building inspector will be out, then thats when all the problems start...... I remember years ago how so many people down there thought they were pretty slick by cheating on the perk test and now so many Septic systems do not function properly. Just take a ride down to St. Georges Island, Piney Point, Point Lookout, where the homes are about at sea level.. I know some of these areas have city sewage now....but those homes were built way before than.
                                                                       Gary

[Dan_Shade]

I'm a bit out of the way, i'm not too worried about snitches, but you're right.  I've decided to definately not put this thing over my drainfield.  concrete truck?!??!! my buddies work for beer, we're mixing!

i know the guy behind me, his lot barely perced when he built.

Is there a huge advantage to having a slab?  at this point, I think i'm just going to move it into the woods where it's pretty level. 

My lot is pretty flat, and has quite a bit of clay, i'm not sure how well it would actually perc now.  A lot of houses built when mine was built (1990) have mound systems, to my understanding, the county no longer allows a mound system for drainfields.

[Gary_B]

  Dan,
   Im not sure if there is a big advantage on a conrete slab., I am just a small operater, and I try to keep the overhead down on what ever I do.  When it comes to my air dry, I built platforms about 16 inches off the ground using locust for the legs, and a deck consisting of 2x4 on 12 inch centers, this gives me a nice level deck, I have built a few, One platform I keep all my 10ft. lumber, and the same with smaller lenghts. When I take a tree down, I try to keep the log lengths as standard as possible, although that can be a problem, due to straightness. From what I understand the codes have really changed in SM, the amount of land you can build a house on and so on. I was down there 2 weeks ago for a funeral and it has really changed, all the homes being built are 2500sq ft. or bigger., most are 2 story's . I will be making the trip once again on Thursday, trying to get in as much fishing in and spend time for with the family.

[Dan_Shade]

yeah, it has exploded in the past 5 years.  dummy me has been here 7, but refused to buy a house for 6 of them...

I could have had 15 acres 6 years ago for what I paid for my place.

why 16"?  i was just going to stack them on top of the cross ties that I have, that's about 8" up.

[logmason]

Quick story about crete slabs. Worked a big job for a homeowner in the city. They asked if I could seal a concrete deck I told them I would try. The deck is open on top with a garage under. The garage was a damp musty wet place, dripped in rain. I mixed linseed oil and mineral spirits 50/50 and sprayed about 5 or 8 coats on the slab. No more leaky. It is my opinion that concrete does not seal water. I have other for instances.

Also I am not a fan of dry lock. I do like cam coat on walls, comes in a bag and you mix with water and brush on.

[Furby]

Dan,
Most people raise their lumber stacks up for a couple reasons.
One is to get away from the ground moisture.
Also to be able to clear weeds easier and allow better air flow both through and around the stack.
It also helps to keep pests away, just a bit.

There is a couple VERY good posts on this subject someplace..........
Here we go! This is just one of them but you get the idea.
http://www.forestryforum.com/board/index.php?topic=4307.0

Read down, there are pics as to how to set it up.
Some use concrete blocks instead of the first cross tie.

[FeltzE]

On an interesting note, This morning on This old House they were pouring a concrete 6 inch thick floor, as a vapor barrier they were putting down 15 lb felt paper and on top of that a plastic 6 mil sheet.


The reason for the barrier is to keep moisture from migrating through the concrete floor to the interior floor above potntially damaging the interior flooring.

Eric