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Moisture and your home!

Here in Middle TN, moisture in your home has been at the top of many homeowners minds due to recent flooding.  Rumors, good and bad advice, and warnings all pertaining to water in a home have been circulating like wild fire.

There are three main keys with moisture in a home.

One is quick action.

Quick action is needed to eliminate standing water in a home, and remove all articles and building materials in a home which hold water, or keep air from circulating freely. I have wrote more on this here.

Second is to not rush dry time.

Many are concerned with fixing their home as quickly as possible. If you don’t allow the moisture to drop to a safe a standard level, their can be a host of problems. Mold, wood movement, and deterioration of building products.  Your home may take 2-4 weeks to stabilize.

The building principle is that all homes have moisture in them.  Their are safe levels of moisture, and unsafe.  I know there have been people running around with moisture meters trying to determine what is bad and what is good.  One day after flood waters leave a home, is premature in testing for moisture content.  Follow the basic rules of remediation, start the drying process, and then test later.  Here are some key facts.

1. Lumber from the mill can arrive at your doorstep at 19-20 percent moisture reading.  This is not unsafe!

2. Moisture readings of 12-16 percent are safe to close up and proceed on with construction.

3. Furniture needs to be at 12 percent or below to be dimensionally stable.

4. Homes in a dry climate will sometimes drop to 6-7 percent but rarely lower.

5. An area to watch is between 20-28 percent moisture reading.  Most flooded areas will drop out of this range quickly though.

6. Above 28 percent for a prolonged time, mold and deterioration are imminent.

Read more about this here.

Third, know when to stop.

Many homes are being stripped beyond what is necessary. Sub-flooring, unaffected drywall, wall sheathing are all examples of items that may not need to be removed. True the appearance of your wood may have changed, but the serviceability for the most part remains intact.

So called dimensional lumber, a 2 X 4, should look the most normal after significant water entry save for some staining.  Plywood subfloor, or osb (oriented strand board) subfloor will many times look grey, obviously dirty, swell at the seams, and flake.  Don’t rush removal though.  OSB and plywood are manufactured with the idea that at some point they will get wet.  If you can imagine a building project in a variety of rainy conditions, these substrates need to remain serviceable while getting wet.  Allowing them to dry sufficiently before covering is important, but appearance isn’t primary here.

If in doubt call an engineer to check out your particular situation.  Most engineering companies will perform a site visit for 300-400 dollars, much less than the cost of replacing your subfloor.  As a note, particle board or mdf, as seen in lower end cabinets and at times under carpet, is a complete loss.  Remove as quickly as possible. Also, if you are installing hardwoods, have them acclimate to your home for at least 3-5 days before install.  This will keep them from excess movement after install.

Feel free to read more here.

So how do I test?

For the homeowner, buy an inexpensive meter.  This type of meter will have prongs that you will push into the affected areas, with a gauge displaying moisture content.  This is easy and necessary insurance before you start covering up walls and floors.

Check this one out, available on Amazon. There are better, more accurate ones out there, but for the average home owner this should suffice.


Yes water in your home is a call for action. Just don’t act irrationally. Knowing the rules can save you big bucks.



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6 Responses to Moisture and your home!

  1. Amy Halleran @BeyondCreatives May 16, 2010 at 9:42 PM #

    I’ve read a couple of your posts because we were impacted by the flood. Our damage was minor compared to many of our neighbors in Rebel Meadows. We were lucky. We had a foot in the garage and in the crawlspace requiring all of our duct work and insulation be replaced. Our HVAC is working, but we have been advised to get it replaced too because of water intrusion. In the process of arguing this with the insurance company, no other work has started. Our duct work and insulation have not been removed. Is that something to be concerned about or do we have more time to get things done?

    Thanks for the great info!

    • Chris Crimmins May 17, 2010 at 6:30 AM #


      Those are great questions. If the insulation you are speaking of is inbetween each floor joist, yes it poses a large threat. For one, it won’t let the subfloor dry, and in this warm weather, should start to support mold quickly. If the insulation is along the foundation perimeter, and air is being forced into the crawlspace to dry your floor, it poses less of a threat. I am supposing the insulation is fiberglass bats with paper backing. Let me know if yours are different.

      For the HVAC, whatever you do don’t run the unit. This can force air born contaminants from the ducting into your home, such as mold. I have been instructed by codes that HVAC units are one item that can be repaired, as opposed to being replace. The caveat is that floodwaters have a way of eating the insides of the units. So the unit usually has a much shorter life span. But for some, paying out a few hundred now for the repair, and saving for a new unit is a better option. The ductwork must be replaced. As far as immediate danger, it is secondary to insulation between your joists. But once again, leave the fan off.

      Thanks for responding, let me know if you have any other questions.

  2. Amy Halleran May 17, 2010 at 10:03 AM #

    Thanks for the quick reply Chris. The insulation I speak of is wrapped around the duct work. Oddly enough I don’t have any insulation in between the floor joists. I purchased the house in Sep 08. It had an inspection completed on it but it wasn’t noted that there wasn’t any insulation. Is that common? Should we have it installed when the duct work is repaired? Should I have a water barrier put down in the crawlspace? It doesn’t have it now but we have also had concerns over musty smells at times.

    • Chris Crimmins May 17, 2010 at 11:56 AM #


      The duct work insulation will hold moisture. There is a laborious way of saving hard ducting, but for most, it is just cost effective to remove all duct work and reduct.

      Insulation between the floor joists or a perimeter insulation is a minimum of what a home needs to reach code. Also a plastic vapor barrier covering the entire crawlspace is extremely important for keeping water vapor from affecting your home. That musty smell more than likely is elevated humidity, and inadequate air ventilation.

      Depending on your particular situation, you may want to look into a perimeter insulation, such as closed cell foam, installation of a vapor barrier, and a conditioned vent into your crawlspace. Your ductwork will be happier due to a consistent temperature, your floors will be warmer in the winter, and the musty smell should go away.

      Let me know if you need pointed in the right direction for all of that work. Pulling that ductwork out sooner than later will be beneficial. Another week or so shouldn’t hurt your home, just might be more unpleasant on the removal. Just don’t push air through the ductwork.

  3. Matt March 8, 2011 at 9:37 PM #

    Chris –

    I recently had a termine inspector come to the house and he did a moisture test on the outside perimeter of my house and it came back as around 10% moisture. He said this might be cause for alarm as it can invite termites. My big concern is that with a 10% moisture reading, is the drainage in my house adequate? We are on a crawlpace on a slight hill in a cul de sac and the house is only a year old. I want to ensure I don’t end up having a mold problem once the warmer weather starts to hit and all this rain stops.

    • chriscrimmins March 9, 2011 at 8:19 PM #

      Matt, Thanks for the comment and question. 10% moisture content is within normal parameters. It seems the inspector was trying to get work. Above 18 might be a cause for concern, and it isn’t until the mid 20’s that the wood can support mold. I don’t see any problems.

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