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Water Intrusion Question

Daniel Weaver | Posted in General Questions on

Have a friend who had a problem with rain water getting into some stud cavities.  Apparently the contractor came out, took off the siding, found the location of the leak, fixed the problem and closed it back up.

My friend is concerned about residual water in the wall.  Contractor claims that water ran down the studs and hit the subfloor so insulation and interior sheet rock is dry.  Contractor also claims that stud bays were open to exterior for two dry days (this is in Northern California) and everything dried.  Friend wants to have someone come out with a moisture meter to check walls.

Here’s my take/questions.  Sheetrock and insulation should be replaced (we’re talking 6 stud bays here).  It is my understanding that moisture meters only measure content of material that they are in contact with (e.g., concrete slab).  Putting a moisture meter on a painted sheet rock wall is not going to reveal moisture in stud bay cavity or insulation.  Truth or fiction?

Thoughts?

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Replies

  1. Chris Koehn | | #1

    If the stud cavity was well and truly opened up to the exterior for two full dry days it may indeed have dried out. How old is the house? Is there a vapour barrier in the wall, and if so, where? What kind of sheathing? Was the sheathing removed or just the siding? What kind of siding?
    The issue here is: is there enough moisture left to support mould growth and/or decay. The answer is: it depends.. on how the wall is constructed.

  2. GBA Editor
    Martin Holladay | | #2

    Daniel,
    Do you have any reason for your suspicions that the contractor is lying?

    It is indeed hard to determine the extent of moisture in a closed stud bay just by using a moisture meter. The best way to investigate the extent of a moisture problem is by opening the stud by up, not by the use of a moisture meter.

    But that's exactly what the contractor did. The contractor opened up the stud bays, examined the situation, and exposed the stud bays to fresh air for two dry days. Once everything was dried up, the contractor repaired the wall.

    According to the story you provided, it sounds like the contractor did the right thing. So why is your friend so suspicious?

  3. Danny Kelly | | #3

    One quick check you can do that may make him feel better is to look at the wall with an IR camera. Typically used to find active leaks but may still identify residual bulk water if it is cold out. If nothing shows up may be a good sign that there is no moisture/or such a small amount of moisture in the wall that it will dry out without any issues. This of course all depends on the construction of the wall.

  4. David Meiland | | #4

    Here's my take/questions. Sheetrock and insulation should be replaced (we're talking 6 stud bays here). It is my understanding that moisture meters only measure content of material that they are in contact with (e.g., concrete slab). Putting a moisture meter on a painted sheet rock wall is not going to reveal moisture in stud bay cavity or insulation. Truth or fiction?

    I'm not sure there's a problem, and like Martin I wonder why you're suspicious, but here are some further comments.

    First, if there was fiberglass insulation and it got more than a little bit wet, it probably should have been replaced. If it was soaked, two days with the wall open was not enough to dry it out, except maybe in Death Valley. Obviously this is a judgement call and none of us can see how wet (it at all) the insulation got. Drywall can usually survive a short-term leak pretty well.

    Second, there are a couple of possible moisture meter options. The Tramex MEP can find moisture that is directly behind sheetrock but hasn't soaked the sheetrock yet, maybe to a depth of 1" to 1-1/4". It is a pinless meter. Using a typical woodworker's pin meter on drywall does nothing unless the drywall is quite wet, in my experience, at which point you can see it anyway. Someone scanning the wall carefully with a MEP (both known dry areas and the repaired area) would be able to get a picture of whether there's moisture in the wall. There are other meters like the Protimeter Surveymaster that have long pin probes that can be put into wall cavities if you are willing to have a couple of small holes in the surface. You can sometimes go right thru from the inside and meter the sheathing, or go thru above the baseboard and meter the bottom plate.

    IR could be useful also, under the right conditions (which you can usually create for the purpose of inspecting).

    If someone handed me this problem, I would probably scan with the meters and/or IR, and I might find something. The question would become, how significant is it? In a lot of cases you have to interpret the meter readings and try to decide how much destructive investigation is warranted. If the meter is in the red all over the wall, that's probably a clear sign of a lot of moisture, but if it hits a few hot spots here and there, is that a problem? It can be hard to tell.

    You might want to do some metering now, and then some followup in a month or two, Keep a map of the readings and see if they are changing.

    Since you're the one investigating this for your friend, I would talk to the contractor directly and ask specific questions about how wet the wall was, what he replaced, etc.

  5. David Meiland | | #5

    Why am I unverified when I post from my laptop? It has my name and email address filled in...

  6. Daniel | | #6

    "Daniel,
    Do you have any reason for your suspicions that the contractor is lying?"

    Uhhhh...I don't think I ever mentioned or insinuated that the contractor was lying, just relating what he did - I was thinking that there might have been some residual water in the fiberglass batt insulation that was not replaced and how to test for for it without opening the wall - no bias against the contractor here.

  7. GBA Editor
    Martin Holladay | | #7

    Daniel,
    You wrote, "Contractor also claims that stud bays were open to exterior for two dry days (this is in Northern California) and everything dried."

    So that's what the contractor said. So why do you need a moisture meter -- unless you think the contractor wasn't telling the truth?

  8. Mr. Greenguy | | #8

    I don't think a moisture meter will tell you anything, but unless the wall was soaking wet when they put it back together you should be fine. I'd be more concerned with how the contractor 'sealed' up his work and how these new openings into the wall will keep out future water. Did he cut the siding and the moisture barrier and then caulk it back together? If so, the problem hasn't been fixed.

  9. Michael Chandler | | #9

    A thermal camera would show the presence of dampness better than a moisture meter but I agree with Martin that it seems like the contractor took appropriate action and further that it should not be necessary to replace Sheetrock and insulation unless they show signs of damage or mold so long as they were clean and dry when the wall was closed back up.

  10. Chris Koehn | | #10

    I'd like to re-direct you to (1): the contractor may be correct, so long as he actually opened up the stud cavity to the outside. If he didn't, it's anyone's guess, and the cheapest and most effective way to find out if water persists in your wall is to open it up. Drywall is easy to fix (perhaps it's best virtue)..

  11. Riversong | | #11

    Daniel,

    You really need to supply more information in order to get a useful response.

    You say the contractor removed the siding, determined where the water had run and left the stud bays open to the exterior for two days. Does that mean he also removed the WRB and sheathing, which you failed to mention?

    If not, how was it determined that the insulation was dry? If so, how was the sheathing and WRB patched/repaired/replaced? What was the leak that was found? What kind of insulation is in the stud cavities? Is there an interior vapor barrier?

  12. Daniel Weaver | | #12

    Appreciate the answers here...a point of clarification. Never meant to suggest that the contractor wasn't telling the truth, so when you suggested that I thought he might be "lying" it seemed like a mischaracterization of my inquiry. One can relay their take on a situation and be incorrect in their assessment - this does mean that their intent was to lie. For instance, one can do a visual inspection of fiberglass insulation and it could appear to be dry yet have residual moisture inside. In retrospect, I should have phrased my question around moisture detection in closed walls.

    My friend who has some allergies was just asking me a question regarding the possibility of there being residual moisture and how to detect it if need be. In retrospect, I should have just stated that.

    Again,I appreciate the help and the wisdom of all on the site.

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