Replies

1. 
   Guest_ | Aug 17, 2000 06:37am | #1

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   Control you mositure first and find out why you have all the cracks. Seems to me you may have a structual problem on you hands. If you don't get rid of the moisture you are going to end up with mildew and all sorts of other problems.

1. 
   Guest_ | Aug 17, 2000 01:43pm | #2

   *Ken, lets go back to square one.First of all the spider marks that show up when things are damp, are not uncommon.What I would be more interested in right now is the original cracks in the walls. 6 cracks that leaked is not common. How big were these cracks and how were they positioned? What was done to seal them?The cracking in the walls and slabs is a sign of something being wrong. Either the concrete supply, concrete contractor or the base on which you are founded has a problem.A little bit more info would go a long way to focus my answer to you.Gabe

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   Guest_ | Aug 17, 2000 09:38pm | #3

   *Ken - Were you around when it was built? Do you have any idea about the following:Concrete thickness? 6 x 6 welded wire fabric? In proper position? Mix design? Vapor retarder (plastic)? Drainage fill (crushed stone) thickness? Subsoil conditions (general)? Water table (sump pump in a new house indicates an issue)? If you weren't there, what do the drawings show? Many 1/4" cracks in the slab are NOT normal, and indicate, most likely, a problem with one of the above, or a combination. As an example, a high water table, 2" crushed stone (instead of min. 4"-6"), no vapor barrier and WWF not hooked and pulled up - and you're there.All of these can impact your condition, and might dictate how and if you finish. For instance, if the vapor barrier was omitted, you need to add one above the slab - this would certainly affect your choice of floor treatment, etc. As far as the walls go, what was used for backfill? Combination of high water table and poor quality backfill = hydrostatic pressure on foundation walls = cracks. How thick are the walls vs. how deep the basement? How waterproofed?PS - A control joint is i supposed to crack, and contain the crack. 1/4" is abnormal movement IMO, depending on the joint spacing. They can be sealed with an appropriate sealant.Jeff

1. 
   Guest_ | Aug 17, 2000 11:23pm | #4

   *You don't say where this house is, but have you checked for structural failure due to unstable soils? This sounds like a common problem in some areas, like S. Arizona and E. Colorado.If unstable soils is the problem then your best bet, even though expensive, is to have a local engineer of expert of some sort look at the problem and recommend a solution.

2. 
   Ken_Kelsay | Aug 18, 2000 11:37pm | #5

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   Actually, I've had 7 cracks fixed with epoxy injection. All the cracks ran from the top of the wall to the basement floor. At this time there are 9 other similar cracks that haven't leaked, so I haven't had them fixed. The house was 6 months old when we moved in. We're the second owners. Judging from what I've seen as they've constructed other basements in the subdivision, I'm guessing that they ran the concrete way too wet to make it easier to fill the forms. I watched a crew do the house across the street, and they kept asking the driver to add water. I talked with a structural engineer I work with and he agreed that would cause my problem. We live in the St. Louis area and the soil has a lot of clay. The house seems to be pretty stable. There's not much vertical displacement of the cracks in the floor. I may have been mistaken on my humidity numbers in the first message. I was recalling from memory. I have a thermometer in the basement with a humidity meter. Over the last couple days it's been high 40s or low 50s for humidity in the basement. It's been hot and humid outside with humidity as high as 80-90% over the last couple of weeks. The walls are 8" thick. I have no idea about rebar in the walls or floor. I would guess not.

1. 
   Ken_Kelsay | Aug 18, 2000 11:43pm | #6

   *Jeff,Please see my response to Gabe for most of the details. I have no details of the actual construction. I would guess no rebar or woven wire based on the others I've seen poured in the subdivision. I don't know about backfill either. I've done some work around the foundation to get it sloped away from the house as much as possible. Basements with sump pumps are pretty much the norm around here. I believe it's common to install the pump when the house is built. Obviously, I don't want any moisture problems if I finish part of the basement. I'm just in the planning stages of that project. Thanks for the input

3. 
   Guest_ | Aug 19, 2000 12:41am | #7

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   Hi Ken,

   On the surface, it would appear that you do have problems. How serious would have to be determined by a tech audit. You can have a testing company test the concrete, either using a hammer test or better yet, take a core sample and do a break on it to determine compressive strenght. The same company should be able to determine if any rebar was installed in the walls. I use a Hilti bar detector and most testing firms have them or something similar. They can excavate of expose your footings on any given location and test the soils bearing capacity both beside (with a Proctor) and underneath (with a metal rod for resistance) your footings. They can core drill your basement slab and examine the composition, depth, compressive strenght, rebar or mesh, vapour barrier, soil settlement and sub base.

   This sounds a little complicated but its SOP for testing firms.

   Once you know all the answers to the construction of your home, you can easily learn the solution and plan of attack to give you a comfortable environment.

   OR YOU CAN DO WHAT I NORMALLY RECOMMEND...

   Cover the outside perimeter with baseclad SM, followed with vb and then drywall. On the floor, install vinyl tiles and small area rugs or cover with 6mil poly and install a wood floating floor. Install a small dehumidifier in opposing corners if problem persist.

   Gabe

4. 
   Ken_Kelsay | Aug 19, 2000 05:11am | #8

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   Gabe,

   Thanks for the response. I need a little clarification though. I'm a Mechanical Engineer by training, but have little experience in residential construction. I'm a long-time subsciber to Fine Homebuilding. I understand vb and drywall, but I'm not clear on baseclad SM. Please explain. My thought as far as walls go was to set a stud wall out from the concrete surface of the wall far enough to clear the plastic tubes that remain from the epoxy injection on the cracks. That would also allow me to make the wall perfectly straight versus drywalling along the concrete, which I'm sure is not straight. It would also leave some airspace between the concrete and the stud wall. I haven't done enough research yet to know what I would do with any insulation or vapor barrier if I constructed the wall in this manner. I intend to finish only part of the basement. I thought with this wall arrangement it would allow air to move from the space between the concrete and the stud wall to the unfinished portions of the basement. In my mind this would allow damp air to migrate to those spaces and be dissipated. Is this sound thinking?

5. 
   Guest_ | Aug 19, 2000 03:37pm | #9

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   Hi Ken,

   Baseclad is a SM styrofoam 2 by 8 ft. c/w recesses to accept either a metal strip or a wood strapping to screw the drywall directly to. The baseclad acts as a vb as well.

   If your concrete wall is too uneven to attach directly to it, you can frame as you suggested. What I have done in the past is frame the walls with 2x2 galvanized metal studs and install the 1 1/2" SM between the studs. I also drape felt paper down from the ceiling and attach it with a 1x2 strapping to the ceiling and it hangs loose about 2"from the floor. Overlap the sides by at least 2 inches.

   Shoot or screw the bottom track to the concrete floor over a 1/2" asphalt impregnated board. Because that the SM is not continuous with this application, I do use a poly vb and then I install the drywall leaving a 1" gap at the bottom.

   Hope this helps

   Gabe

1. 
   Guest_ | Aug 19, 2000 08:19pm | #10

   *Ken - If you test the concrete and it tests out above 2,500 psi, the problem could be expansive clay subsoil, such as bentonite. Bentonite, while useful as a waterproofing product, can cause serious structural problems when existing as an unexpected natural deposit. It runs in layered 'lenses' in shale and limestone strata in many areas of the US, including St. Louis. It is a type of clay referred to as montmorillonite, one of the smectites.Because variable amounts of water can be held between the clay layers in natural deposits, the layer spacing can expand and contract depending on the amount of hydration. This may cause a great deal of structural damage to buildings sited on soils with a high smectite clay content. For instance, a sump pump draining the area under the slab and allowing it to experience variable degrees of saturation could exacerbate the problem.Of course, this is probably more than you wanted to know, but might point you in the direction you should go with respect to further investigation.Jeff

6. 
   Ken_Kelsay | Aug 19, 2000 08:25pm | #11

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   My house is 3 years old and the basement floor has many cracks. The control joints are all cracked with some open as much as 1/4". In the field created by the control cracks, there are multiple "spider" type cracks which are all fairly tight. Additionally, I've had 6 cracks in the basement walls repaired to stop active leakage. The basement has a sump pump connected to drain pipes under the slab I believe. This amount of cracking seems abnormal to me. There is currently no active leakage, but the "spider" type cracks appear damp during wet periods. I run a dehumidifier and have tested the relative humidity at approximately 60-70% with a sling psychrometer. I would like to partially finish this basement. Is that realistic and what precautions should I take?