Moisture level question

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Old 04-28-17, 04:09 PM
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Moisture level question

Hi guys

Not sure if this is the right section but I am looking for an answer to this:

"what is the accepted threshold for moisture level inside a wall"

This would be for an outside wall, when testing with a probe. Is it 10%, 20%, 30% etc.

Thanks.

Mods: if this is the wrong section, I apologize.
 
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Old 04-29-17, 06:10 AM
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Forum is fine, as we read them all. Ideal is zero. Now to the real world. The moisture will be determined by your location, normal relative humidity, insulation value, vapor barrier (whether installed or not). You really don't want zero, as it would be detrimental to the wood. So a low percentage of moisture is not out of the question. Of course we have to ask..........what is the problem, and why do you need to know?
 
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Old 04-29-17, 06:38 AM
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Some of the units in my development have moisture problems, and some contractor did a study and the report came back with 20% as the threshold, and people are disputing that number. Basically, the contractor is saying anything above 20% is a problem and stuff should be replaced (rip out exterior and do it over). Some of us are skeptical on that approach.
 
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Old 04-29-17, 08:57 AM
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HE may be trumping up business. Face it, your inside humidity is probably in the 50% range, especially in summer. So what would keep that from entering the wall cavity? Certainly a vapor barrier would help, but the moisture will still extend to the back of the wall covering at the least. So, unless other information is brought to light, I would say 20% is respectable. Wait for others to chime in on this as they may have other ideas.
 
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Old 04-29-17, 09:54 AM
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Hi fx, can you clarify what they are measuring, humidity or moisture content of some part of the wall, the drywall or the studs? If they are measuring the studs then 19% is considered dry, 20% almost dry. If they are measuring relative humidity that will vary with outside humidity.
Moisture and Wood

Can you explain what the moisture problem is? There are common sources of moisture like outside humidity and NJ does have its share of that. Are you near the shore, over by Philly, or up in the gap?

Bud
 
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Old 04-29-17, 03:33 PM
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The issue is that some buildings here have had leaks and moisture issues. The culprit is a combination of flashing either not installed, or installed improperly. There is also an issue with stucco and EIFS. There have been issues with gutters, windows, Tyvek, you name it. Some exterior walls have already been repaired. In other places, holes were drilled and a probe inserted to measure moisture. The results are mixed. Some spots have high (like above 50%) readings, and others are around 20%. The report calls out anything over 20% as a problem, so it is hard to determine the extent of the problem overall. I personally think that up to 30%-35% might be OK, which would then reduce the number of areas to address by a lot. That said, I wouldn't want to let some poor soul be exposed to mold or whatever.

It is true that this company is drumming up business, since they have been here for a while doing the more pressing repairs. I am just a concerned resident trying to cut them off at the pass before I get slammed with an assessment or whatever.
 
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Old 04-29-17, 04:09 PM
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Sounds like they are measuring humidity which is called Relative Humidity for a reason. What they need to include with that measure number is the temperature at the same time in the same place. Here is a simple calculator to play with.
Temperature, Dewpoint, and Relative Humidity Calculator

A quick example. If they measured 20% at a temperature of 50 then that would be similar to an inside humidity reading below 10% at 70 degrees and that we all recognize as very dry.

In a cold climate the vapor retarder is normally placed on the inside and the wall cavities are expected to dry to the outside thus modern house wrap allows moisture vapor to pass through it.

Where they have experienced actual leaks we would of course expect that area to read high, but it should dry out or at least equalize with the outside air once the leak is fixed.

Do you know how the wall assembly is constructed? Example, inside to outside. Drywall, vapor barrier, insulation sheathing, house wrap, siding. As long as there isn't a vapor barrier on the outside or an ongoing leak everything should be ok.

Bud
 
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Old 04-29-17, 04:36 PM
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Bud,

Drywall, vapor barrier, insulation, sheathing, wrap, stucco.
 
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Old 04-29-17, 07:48 PM
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Sounds like once the leak is fixed those walls should dry to the outside with no problem, assuming the stucco doesn't present a problem, no stucco up here.

From your explanation I get the impression these leaks have been an ongoing problem. If many cases water leaks are NOT actually leaks but condensation problems from air leaks. One distinction that separates the two is the season during which they occur. Condensation and related ice will form during cold spells and melt when things warm up. I've seem several shingle jobs that thought they were fixing the leaks only to have the same problem return sometime later.

Have any of the repaired building had recurring problems?
Have they tested the wall cavities of problem homes after being repaired to confirm the problem was corrected?

Bud
 
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Old 05-01-17, 12:58 PM
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A few buildings have been repaired, and the problems have, for the most part, stopped. In some of the repaired buildings, other (new) areas presented problems of the same kind. A few theories with the stucco cracking are how (when) it was applied (cold weather in some cases), and is the cracking a result of the new building ""settling". Yet, some buildings have no issues.
 
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Old 05-01-17, 02:05 PM
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Stucco is not at all my field so I pulled up an article I thought might help or at least explain some of the problems. Hopefully others here on the forum will have more experience with that method of building.
To Install Stucco Right, Include an Air Gap | GreenBuildingAdvisor.com

Bud
 
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Old 05-01-17, 03:32 PM
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Thanks, Bud

This helps a lot
 
 

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