This is Kenneth Hellevang of an agricultural engineer with the NDSU Extension Service and we're looking at a series of clips on cleaning a water damage restoration in house and this is the final of five video clips in the series. This one is on drying the structure, it's very important that we focus on drying the structure because that's what's going to prevent any mold growth in the future and mold remediation.

As we found in the earlier presentations is indeed a health hazard and we don't want that mold in our home or it'll start causing us respiratory problems in the future so the structural drying is a critical step in the cleaning a water damage restoration for structural drying to occur, we need to open all of the enclosed areas so we're talking opening. Opening the walls if we have the floor even if it's vinyl and we got water underneath. We need to open them up, so that we can dry and this drying may take just several days or it may take weeks it'll depend on the drying conditions or how much airflow that we have gone through.

The structure shown here is two different pictures of homes that are in the flood drying cleanup process and I want to show the house. On the left there, you can see the white discoloration that is on the brick facing and that's because moisture is coming through the concrete, we have this effort for the essence of moisture that comes through and as I indicated in the earlier slide the critical that we make sure that the weep holes are open so that the water drains out and then we need airflow both on the inside of the structure and on the outside to facilitate. That drawing on the picture on the right that moisture is showing up has a darkened color and again it's indicating moisture is coming from the structure and if you look closely you can even see that there's moisture inside the house and there will be condensation issues on the windows. If we're not getting that moisture, removed from the home and if we don't keep the humidity level low enough that's going to lead to mold growth for certain and probably structure as deterioration as well. 

The drying process really involves circulating air across those surfaces we need to get them opened up. We need to get airflow blowing against that surface to aid in the drying process and then we need to make sure that the air that we're moving across the structure is dry air. The way that we do that is to bring outside air in that's dry and it picks up moisture from within the house and then we exhaust that to the outdoors and what we recommend is that you put a fan in the window facing out again so that we're drawing the air into the house and in blowing the air to the outdoors to get a good suction created. Within that, we can remove gallons of water a day with moving outdoor air through the house where most of our home dehumidifiers are going to be taking out pints of water per day. So once we start getting the structure, dried down then we can go to using no fires but initially what we're going want to do is to be using a lot of outdoor air moving by to dry the structure.

I really encourage people to be measuring the relative humidity to know how we're progressing with the drying process and humidity gauges are available both in a digital format as well as the mechanical types regardless of which one you're using I recommend that we calibrate it to make sure that it's giving us accurate readings. The best way to do that is to take a cup put a quarter cup of salt in there a half a cup of water into that cup put it into a plastic bag like a gallon ziplock. Put the cup and the meter in there seal it up and now let it sit for 12 hours after that 12 hour period we would expect the relative humidity. Within the bag to be about seventy-five percent assuming room temperature and so that'll give us an indication of whether the meteor is giving us an accurate reading or not. Then we can probably modify the reading to give us an accurate reading and what we want to do is to measure the humidity in the house we

have since mold will grow at humidity at levels exceeding about 70 percent our goal should be to keep the humidity
level.  The in the home structure under 70 percent moving a lot of airflow through to keep that drying process going and keeping the humidity level under 70 percent during that drying process particularly as we start getting later.

Into fall and into cooler temperatures or in the spring if we're looking at spring flooding we can and enhance the moisture-holding capacity by adding heat to the air but it's important that we do both warm. The air and move the air or exchange the air that's within the house, the other thing to keep in mind is that the warmer it is the more rapid mold will grow and so there's a little bit of a balancing act. Generally, what we look at is keeping the air temperature in the home or in the structure under about 72 degrees that's warm. Enough that get good evaporation occurring good drying occurring but we're not so wired that we're really enhancing the mold growth. But we need both the warmth and exchange in the air if we don't have the windows open to bring dry outside area and we're just going to create a Sun that we're going to have warm moist air in the house and not accomplish drying and so we need to still at least.

Periodically be opening the windows getting the air exchange as well as having the warmth to help enhance the evaporation we need to continue drying until the moisture or the content of the wood is low enough that we're not

going to have mold growth and typically what we're looking at with mold growth again is moisture contents of the wood exceeding about 15%. Our goal should always be to get the moisture content the wood below 15% as quickly as. We can and also we can't be enclosing any walls or doing any reconstruction until we're below that 15% moisture content and what we have on the slide here shows that at 70 percent humidity at roughly room temperature that puts us at just under 15% moisture. You'll see different numbers some will say we need to be a down to 13 percent moisture to assure that we're not going to have any mold growth and that is going to be safer but certainly we need to be under 15%. The only way that we're going to know when the moisture content is low enough is to use a moisture meter.

Actually check the moisture content of the wood and check the moisture content of materials. There are a couple of
different kinds of meters some of them, actually have little pins on the end that you push into the wood and major

the moisture content or the material others have some pads on the back and you just set it on the surface and it will measure the moisture content. That way, but it's important that either you check the moisture content or have someone else, check the moisture content before you do any rebuilding. Make sure that the wood is dry the NDSU Extension Service has moisture meters available in our county extension office's that you can check out and use to check the moisture content many of the contractors.

Other places will also have meters but look to make sure that you're getting an accurate moisture reading verify what the accuracy of that meter is that you're using to assure that the moisture content is low enough for safe rebuilding the saturated soils will take a long time to dry out and so we can very quickly dry out the main floor the structural wood. 

But when we start talking about basements it's going to take a long time for the moisture that's within the soil to dry out and that moisture will be moving into the basement. It may initially come in as shown in this picture in liquid form but more frequently it's going to be in a vapor form and so it will look dry. But there may actually be gallons of water

per day coming through the concrete which is fairly poorest of to vapor and it'll come through in that vapor form and add to the moisture load in the home. So we need to be concerned about keeping the ventilation going not only to dry the materials but to handle the moisture load that will be coming in through the basement.

One of the things that we recommend and to really determine if the moisture is still coming through is to just take a piece of clear plastic maybe a couple two or three feet on the side tape it to the floor tape it to the wall make sure

that it's taped tightly to that surface. Let it sit there for a day or a couple of days and look to see if moisture accumulates on the backside it'll actually show up as condensation on the plastic it may show up as discoloration or darkening of the concrete. But look to see if that moisture vapor is still coming through and that'll give us an indication of the mono moisture that's coming through and whether it's going to be safe to start rebuilding and frequently.

We're looking at this dry down process in the basement of taking months and so even though the main floor we can dry and probably rebuild fairly quickly in the basement rebuilding really needs to be delayed until we're can be assured that there's no moisture coming through. Another thing that will frequently see after a flood event or when we have a lot of moisture in the soils is that we have this white fluffy material that shows up along cracks and the floor or maybe even just showing up on the concrete floor.

On the con block wall as shown in these pictures and that does not mol what that is is a salt within the soil and as the moisture moves through the soil it picks up the salt as it comes through the concrete the moisture evaporates into the air and leaves the salt deposit behind and when it typically will look like a white fluffy material and you can determine. If it's a salt by putting a little bit of water on it and it'll typically dissolve or there are some salts where you need to put on a little bit of vinegar for it to dissolve. But most of our just a few drops of water and you will see it disappear and a fairly easy way to determine whether it's salt or whether it's its mold growth and frequently it's going to be salt accumulation and it really doesn't create a health hazard but is an indication of moisture coming through the soil and it will continue until that moisture.

Around the house has dissipated in that areas all dried out so that brings us to the end of the section on drying your home and how important it is that we do dry out the structure this series of five video clips hopefully will help you as you look at doing the flood damage cleanup in your own home or if you're looking at having someone help you with it to know that the steps that they should be going through.

So this has been Kenneth Hellevang agricultural engineer with the NDSU Extension Service and we have a lot of information available on our website that you can find by just doing a search flood restoration NDSU Flood information.