Basement Moisture Problems

We are experiencing heavy rains in Minnesota and Iowa this week, and some places are seeing flooding.  Most of us think that flooding only affects a building when the river rises high enough to reach the house and force its way in through windows and doors.  However, there is another way that water can invade your home when flooding conditions are present.

Not too many years ago, Southeast Minnesota experienced a series of heavy rain events over a period of  several  days.  All the rivers and creeks were running high, and the ground was totally saturated.  We were spending a weekend at our recreational home and were watching the 10 p.m. news when we heard an emphatic knocking on our front door.  I opened the door and was greeted by a deputy sheriff who informed me that the river behind our house was rising rapidly.  He encouraged us to leave as quickly as possible.  My wife and I went outside to see the current condition of the river and were greeted by several of our neighbors.  A city dump truck had just arrived and was unloading a pile of sand and some bags for sandbagging.  To make a long story short, we all wound up sandbagging throughout the night and the river began to recede about 7:00 a.m.

At this point the sandbag brigade began to break up, and we returned to our house feeling good that we had escaped the flooding.  Wrong!  As we entered the house, we noticed a plastic basket floating at the bottom of the basement steps.  I went down to investigate and discovered several inches of water.  How could that be, the river hadn’t gotten any closer than the base of the sandbags 20 yards behind our house.  It didn’t take long before we noticed little rivulets of water running down the inside of the CMUs.  The ground was so saturated from a week of steady rain that the pressure difference between the outside and the inside was forcing water through the concrete block.

Fortunately, I was able to procure a gas pump and a sump pump in a nearby city (there was an area for a sump pump in the basement floor when we purchased the house, but we had never put one in place) and after a few hours of pumping with the gas pump, the bulk of the water was out of the basement and the new sump pump was able to keep ahead of the seeping.  The good news was the water in the basement was clean groundwater, and there wasn’t a stinky flood residue to clean up.

Here’s the point.  It is possible for any home with a basement to experience what we experienced that weekend; you don’t have to be near a stream to experience major water in your basement.  Are you prepared for a situation like we experienced?  Have you installed a basement moisture management system?  Check out the Wet Basement Solutions from MTI to see what I am talking about and save yourself some worry and major property damage.

Those are my thoughts, I would be glad to hear yours!

You can see the water that pressure forced into the basement.

Water forced into by pressure differential.

Water being pumped from basement

Notice the water being pumped from basement and the sandbags between us and the river.

What Is A Rainscreen?

What is a Rainscreen?

The term rainscreen (rain screen) can be defined as the first interruption between conditions that exist on the outside of a walled building and conditions that are required on the inside of a walled building. In order to be effective at managing moisture, the rainscreen needs to stand off from the moisture resistant surface of the structural back up wall. There must be a permanent, predictable void between the backside of the rainscreen and the exterior facing surface of the moisture resistant material (WRB) on the surface of the structural backup wall. This void is the rainscreen drainage plane.

What is Rainscreen Drainage Plane?

The exterior surface (veneer) of the rainscreen building envelope is not expected to be waterproof, but it will block most of the moisture. The rainscreen drainage plane behind the veneer should deal with any moisture that penetrates into the building envelope, either from the outside or the inside. An effective rainscreen drainage plane will be both a predictable rainscreen drainage plane and a predictable pressure equalization plane.

According to Toolbase.org, “Rainscreens effectively ‘drain the rain.’ They control powerful building wetting forces-gravity, capillary action, and wind pressure differences.” That’s the beauty of a rainscreen building envelope, and probably the reason that so many new structures feature them.

Unfortunately, much of the material that is passed off as rainscreen drainage plane violates some of the necessary criteria to be effective. Remember, an effective rainscreen drainage plane must be predictable. It shouldn’t collapse under pressure. When cladding is applied to furring strips or mesh drainage plane, there is a tendency for waviness and nail drive-through. Most experts agree that at the very minimum, a 1/8” predictable void is needed for effective drainage. Is a patterned WRB providing this kind of space? Additionally, moisture that is forced to wander around a maze of interwoven fiber certainly isn’t exiting the building envelope very quickly! Even a small amount of moisture left for any period of time in the building envelope will cause problems!

One other issue related to effective rainscreen moisture management is the weep at the bottom of the wall. The best rainscreen drainage plane will be rendered impotent if the water can’t escape the building envelope when it reaches the bottom of the wall. Effective weeps have three critical characteristics: they are plentiful; they are at the lowest point of the wall; they allow water to flow quickly out of the building envelope.

Finally, when it comes time to select rainscreen drainage plane for your project, are you dealing with a company that specializes in rainscreen drainage, or are they just moving product? Will they work with you to design an effective rainscreen drainage “system” for that project? Can they provide all the material, and have these materials been designed to work together?

These are all important issues that are too often not considered when designing a building with rainscreen technology.

rainscreen failure

No Rainscreen Drainage Plane Protection