Continuing from last newsletter, we mentioned we would share with you how you can rid yourselves of the harmful moisture vapor impact under your slab, post placement of slab. I know I will get letters on this from a lot of uninformed engineers. Remember, I don’t pull this information out of my ear. In fact what I’m about to share, didn’t come from an engineer, contractor or a major organization. It came from a hydrologist. Now, that’s a concept: ask a hydrologist on how to manage and move moisture.
The first thing I learned from him was the four different forms of moisture (yes four). You have vapor, liquid, solid and absorbed (your body is 75% moisture and it is absorbed moisture for the most part). The important thing to note here, is that moisture moves differently in each form and that moisture can and will change its form in order to keep moving. Many laws of physic govern moisture movement. Remember, I only have one page to discuss this issue. The most basic law is that moisture will always seek its opposite. Meaning, cold wet, will want to be warm dry and conversely warm wet, will want to be cold dry. High will want to be low and low will want to be high. To accomplish that, moisture will change its form to achieve that goal by changing into the form that accomplishes the need to fulfill that law.
So if you want to manage or manipulate moisture, you address it (moisture) in the form it presents itself with the understanding that it can and will defy you by changing it composition. In a floor system (a floor system is considered from the ground to finish floor or coating) you have what they call a capillary brake (6” of crushed rock) sitting on top of a filter fabric which is on top of the subgrade/ground. The capillary brake is design to stop capillary action (movement in liquid form). However, that does not stop moisture from turning into vapor or gas which will rise to the next obstruction and condensing to liquid again.
So, our challenge is to control the moisture that turn to gas/vapor before it reaches the slab and condense back to liquid. How do we do that? We give the vapor an easy way out of that cavity. We create a vent, it’s called depressurizing the slab. If you already have in place an underground radon release pipe system, this point is moot to you. If not, the system you need to employ is the depressurization system. To simplify the description of the system, you core thru the slab just inside the footing with a 4” bore clear through until you reach within 2” inside the capillary brake. You then place a 3” ABS pipe, routing it through a side wall and venting it out to the exterior. It’s that simple. Another method is to drill the foundation from the outside and vent it out over the roof. For you disbelieving engineers out there, it is the same application of radon (a gas) post evacuation. Moisture (in its gas form) is no different. Moisture will seek the easiest route to find its opposite. Without the system, you have this tremendous moisture drawing power within your home’s envelope. When we were kids in Boy Scouts, they taught how to get moisture off a desert floor. We would dig a hole, place a cup at the bottom of the hole, place a sheet of plastic over that, a pebble in the center and (wow!) you got water. Low permeable coating/material will draw moisture if encapsulated to the coating or material. You’ve experienced that, haven’t you? That long drive in a car while seating on a plastic seat, wearing a pair of leather pants all day, wearing rubber gloves, the list goes on. What happens? The moisture is pulled out of your body, and you get wet, because of this law of physics. Well, in regard to your floor, what formula do you think is being created when you put a sealer on the concrete, follow that up with an adhesive, coating on the floor, and a tight envelope of the house (all low permeable items)? You may not be experiencing this problem because the capillary brake is vented. If not, you could/should depressurize your slab.
The first thing I learned from him was the four different forms of moisture (yes four). You have vapor, liquid, solid and absorbed (your body is 75% moisture and it is absorbed moisture for the most part). The important thing to note here, is that moisture moves differently in each form and that moisture can and will change its form in order to keep moving. Many laws of physic govern moisture movement. Remember, I only have one page to discuss this issue. The most basic law is that moisture will always seek its opposite. Meaning, cold wet, will want to be warm dry and conversely warm wet, will want to be cold dry. High will want to be low and low will want to be high. To accomplish that, moisture will change its form to achieve that goal by changing into the form that accomplishes the need to fulfill that law.
So if you want to manage or manipulate moisture, you address it (moisture) in the form it presents itself with the understanding that it can and will defy you by changing it composition. In a floor system (a floor system is considered from the ground to finish floor or coating) you have what they call a capillary brake (6” of crushed rock) sitting on top of a filter fabric which is on top of the subgrade/ground. The capillary brake is design to stop capillary action (movement in liquid form). However, that does not stop moisture from turning into vapor or gas which will rise to the next obstruction and condensing to liquid again.
So, our challenge is to control the moisture that turn to gas/vapor before it reaches the slab and condense back to liquid. How do we do that? We give the vapor an easy way out of that cavity. We create a vent, it’s called depressurizing the slab. If you already have in place an underground radon release pipe system, this point is moot to you. If not, the system you need to employ is the depressurization system. To simplify the description of the system, you core thru the slab just inside the footing with a 4” bore clear through until you reach within 2” inside the capillary brake. You then place a 3” ABS pipe, routing it through a side wall and venting it out to the exterior. It’s that simple. Another method is to drill the foundation from the outside and vent it out over the roof. For you disbelieving engineers out there, it is the same application of radon (a gas) post evacuation. Moisture (in its gas form) is no different. Moisture will seek the easiest route to find its opposite. Without the system, you have this tremendous moisture drawing power within your home’s envelope. When we were kids in Boy Scouts, they taught how to get moisture off a desert floor. We would dig a hole, place a cup at the bottom of the hole, place a sheet of plastic over that, a pebble in the center and (wow!) you got water. Low permeable coating/material will draw moisture if encapsulated to the coating or material. You’ve experienced that, haven’t you? That long drive in a car while seating on a plastic seat, wearing a pair of leather pants all day, wearing rubber gloves, the list goes on. What happens? The moisture is pulled out of your body, and you get wet, because of this law of physics. Well, in regard to your floor, what formula do you think is being created when you put a sealer on the concrete, follow that up with an adhesive, coating on the floor, and a tight envelope of the house (all low permeable items)? You may not be experiencing this problem because the capillary brake is vented. If not, you could/should depressurize your slab.
