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acceptable basement cinder block moisture content?

acceptable basement cinder block moisture content?


  #1  
Old 08-22-14, 05:21 AM
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acceptable basement cinder block moisture content?

I've been battling water leaking from my front porch, down into the basement below. I believe I've found that problem, but during the process, since I wasn't sure if water was also entering at ground level, I had an estimate quoted from a company that does the "water diverting", i.e., drill weep holes at bottom of cinder block, allow to drain into tile drain, pump out to daylight.

So far, since buttoning up the porch area, I've had no evidence of water intrusion at the bottom of cinder block wall. I've now opened up the area underneath the stairs, and found A LOT of what appears to be old efflorescence at the bottom of the adjacent cinder block wall. I've tried 3 times to remove the efflorescence with vinegar and plenty of elbow grease, to no avail. Muriatic acid would probably work, though I really don't want go crawl under the stairs with acid.

That said, I realize the efflorescence means at some point there was moisture behind, or inside the blocks. Question is, is it still happening, or is the efflorescence simply from "past" water issues, or even the curing of the walls when built,...it is a concrete filled wall.

I've measured the cinder block moisture with a simple 2 prong moisture testing device, and in varying spots "beeps" with two much moisture,...according to the tools chart, around 20% moisture, which is supposedly too high.

How high or how much moisture is acceptable at the bottom of a block wall in a basement? I am running a dehumidifier and it is around 47-50% on average. I just don't want to seal the stairs back up if there's still foo much moisture under their.

Again, so far it doesn't look like I need the internal drainage system,...rather, it appears that ALL of water issues originated from the front porch,..which then was running down to the bottom of the block wall, which was giving the appearance of water coming from ground level.

What to do? How much moisture is too much?

Marc
 
  #2  
Old 08-22-14, 05:46 AM
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Moisture at 12 percent or above by weight in organic material is getting into an undesirable range. 10 percent or less is much better. An easy check is to place a non salted cracker against the wall in the area you are concerned with and check it with your meter in about a week. Or you can do a soggy / dry cracker test by taking a bite. For accuracy I use the original weight / dry weight method being I don't own a meter but sometimes use the bite crumble feels soggy test if I'm rushed.
 
  #3  
Old 08-22-14, 06:17 AM
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Interesting method. I'd also read about possibly duct taping a 2' X 2' section of heavy plastic over an area of block. Give it at least 72 hrs. and then check and see if moisture/condensation has built up under the plastic. If so, then that would mean obviously too much moisture. If so, what to do about it?

As a side not, my meter has two selections, one for drywall/wood etc,... and another for concrete, blocks, etc.,... as stated, the chart says up to 20% is OK for block,... but like I said, these blocks are "beeping" at 18 -20% moisture.

If in fact there is still moisture there,... how in the heck will I know if there's enough to warrant the expense of the interior drainage system. I mean, I'd really hate to spend 3200 bucks or more, and then the system NEVER has to shuttle water away. I need to move forward with the fixing/remodeling of the basement,... but am stuck until I'm satisfied I have the water issue's solved.

Thanks
Marc

Marc
 
  #4  
Old 08-22-14, 08:35 AM
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SeniorCitizen - A concrete block or any concrete is not an organic material.

Moisture is not a problem with concrete since it works well below water. The problem comes with the chemistry and compounds created by the exposure to alternating levels of moisture and wetting and drying. Concrete piling fail at the water level in salt water because of the variation(cycles) and the salts that are produced when leached out when they are exposed to the air.

msr0459 -
Look at the big picture and not the details. The moisture could be from the porch above(bad detail) or from the soil around (exterior moisture barrier not effective) or under the wall. Paint will blow off when the dissolved salts in the wall material reach the surface and evaporate the form a salt that expands and creates pressure that will blow off any coating (especially epoxy that comes eventually comes off in even larger pieces).

Concrete block are little easier to eliminate the problem because they are not solid and have cores and the possibility to drain the moisture out with a drain tile system that also lowers the general water table around the structure because if it is correctly placed with the pipe bottom below the bottom of the footing.

This is a lot of detained information and concepts, but a general description of what is probably going on in your situation.

I bought a new home (95% finished) that had a moisture problem that showed up a year later. It was a 4 level(including basement) and the garage on one end (about 50' away) interrupted a natural drainage and water flowed along the block foundation walls to the lower level where it showed up in the basement with moisture on the lower foot or so of the wall and coming up at the crack between the slab and the walls that came about 4 to 8 hours after a big rain. I had a contractor make saw cuts in the floor just inside the footing, removed sections of the slab removed, excavated the soil, put in a filter blanket, gravel perforated pvc and, knocked holes in the block walls on the footing, inserted flexible plastic tubing into the core and ran it into the gravel around the pvc. -It was hard work and I did it in 3 week-ends with help from my 10 or 12 year old son and occasionally with his buddies. It worked perfectly for 8 years until I sold the house with a dry basement - It can be a DIY job or you can hire it out.

Dick
 
  #5  
Old 08-22-14, 01:18 PM
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Thanks for the detailed answer. However, from what I can tell, these block walls are filled with concrete. Would that have any bearing on whether or not "weep holes" would be effective?

Moreover, up top, in front of the porch area,...I've managed to "divert" tons of water that WAS sheeting off the front sidewalk, and obviously sliding down into the dirt in front of the basement retaining wall. Now, that water is being caught as it falls off the sidewalk, and I've diverted it away from the front of house/basement retaining wall, and so far after a couple of huge rains, I've seen NO water enter at the floor/wall junction. It may well be very damp behind the wall though.

Don't get me wrong, I'll for sure spend the money for interior drainage if needed. But again, I have to wonder if "dampness" behind a filled block wall would actually warrant a $3200.00 + drainage system,...if it doesn't get soaked enough to create actual "drainage" to occur,..does that make sense?
 
  #6  
Old 08-22-14, 04:18 PM
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I agree, 20 percent moisture doesn't hurt concrete block at all. The problem is when organic material like dust etc. coats the surface and when we build a frame and drywall or whatever we choose to finish those areas is when the problem begins. I have a concrete block garage with enough moisture just above ground level on the north side where the sun doesn't get to that has an algae I have to deal with.
 
  #7  
Old 08-23-14, 05:12 AM
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Whick keeps leading me back to the main question for me. If I have concrete filled cinder block, that has 20% moisture in certain areas,...does that warrant installing an interior drain tile system, or perhaps I should maybe use a product like "Xypex" that penetrates/seals the block?

Marc
 
  #8  
Old 08-23-14, 06:50 PM
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Xypex is made to work on concrete. You have mentioned that you have cinder block which is not the same as concrete block. They do have a thicker surface coating material which would be troweled onto the cinder block to create a more water resistant barrier but make sure you understand the products.

IMO. you don't need the drain.
 
  #9  
Old 08-24-14, 05:55 AM
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Thanks for your opinion. I emailed Xypex about the concrete filled block. He said the Xypex concentrate would penetrate both the block and the concrete inside the block cells without issue,...then I should put a coat of another one of their products(can't recall which one, it's in the email) to finish it off.

I suppose this will likely be my course of action,...though this same block wall that runs under the stairs, makes a right hand turn and runs another 20-30 feet or so to the other outside wall,...and of course it's framed and has drywall up. I can shine a flashlight down the wall from under the stairs, and I can see the same efflorescence that was/and remains on the blocks under the stairs(after cleaning 3 times). The thought of removing ALL of that extra drywall and treating with Xypex is NOT something I would want to do.

I wonder, if I remove some small sections of drywall, and IF I see no signs of mold or mildew,...and since now my dehumidifier has the entie basement at between 47-50% humidity...could I NOT have to treat that wall with Xypex? Since it is also a concrete filled block wall,...I still think a lot of the obviously older efflorescence powder was possibly from the curing of the concrete....the house is 15 years old.

I do realize that's also a bit of wishfull thinking,...but the drywall framed wall is 4-6 inches in front of the aforementioned efflorescenced covered block wall...and I really have no idea if that section is constantly taking on moisture or not.

Marc
 
  #10  
Old 08-24-14, 12:26 PM
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xypex or keyton - both are capillary invasive & we've had success w/both
 
  #11  
Old 08-24-14, 04:22 PM
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Can't seem to find anything on the product "Keyton". Is there a web address?
 
 

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