A house built on an engineered pier and beam foundation is a great foundation. It’s strong, provides easy access to fix problems like plumbing leaks, and it is less likely to shift in soils with high clay content. But if you have one of these foundations you may be playing a form of the Old Russian Roulette game. Except instead of only one round of ammunition in the chamber of your six shooter, your crawl space gun is loaded with 4 rounds. Your chances of having a water problem in a crawl space are very high. The simple fact is that your home will experience a moisture problem in its lifetime. The real questions is; “Will you be prepared?”
I get involved in crawl space mysteries all of the time. The most common scenario that a home owner tells me goes something like this:
One morning you wake up and head into your kitchen to make that all important cup of coffee. Because you are dragging your feet you notice that the wood floor is rough and uneven in a small area in your kitchen. As you sip your coffee your more detailed examination reveals that your floor at the junction of each plank of wood is slightly higher almost not noticeable than in the middle of the wood plank. It creates a question but it is so small and almost invisible that the clock is more powerful than the little dinky problem of the wood floor. Really not enough alarm to call anyone. And so the cares of life force the little floor anomaly to fade into the background. After all, the floor still looks OK.
Over the next few weeks the floor gradually gets a little worse. Now you begin to worry. You remember that wood reacts badly to water, and the thought crosses your mind; “Maybe you have a leak?” A plumber is summoned, and he valiantly goes below your house looking for problems, but you have no leaks. Now you have the answer to your question. NOTHING IS WRONG.
Well another week has passed and now you know you have a problem. The floor looks like an old fashioned washboard, and there is a noticeable odor. You call your insurance company. The adjuster shows up and once again someone drops into the crawl space. The adjuster informs you that he can see that the floor is cupped (a term that you have never heard before) but they cannot determine the cause. He asks to bring out an expert to determine causation.
The expert shows up and spends several hours inspecting your home and leaves telling you he will write a detailed report. After a week the report arrives. The report is only 80 pages long and you sit with your thesaurus, dictionary, and your daughter’s Algebra II book in front of you as you try to decipher terms like “The Law of Thermodynamics” Plasticity Index of the soil”, “Wood Equilibrium”, and the equation: e2 + (p * v)2 – e1 – (p * v)1 + [(u^2) / 2]2 – [(u^2) / 2]1 = q – wsh Despair beings to impress itself on your life.
The report says you have no problems. Nothing happened. Nothing is broken. You wonder to yourself, “Why if nothing happened and nothing is wrong is my floor damaged? If this sounds familiar, keep reading.
Finding problems under your home is difficult. First of all going into a dark, dank, confined space where you literally must crawl (hence the name “crawl space”) complete with spider webs and creepy critters is a little scary. Even if you are the odd owner that inspects his crawl space three times a year, problems are not usually easily noticed without instruments, and training. The result is that these problems under the floor of your home often go unnoticed and undetected until they are big issues.
Water and crawl spaces are unfortunately, happily married. There are a number of really boring reasons that are all related to the “Law of Thermodynamics”, (an equation that defines moisture migration.) In order to save time will you let me simply say; “that’s just the way it is; or it is because of good ole Mother Nature?” Good!
So what can you do to prevent moisture problems from happening to you? All you need to do is to obey the following rules. The rules listed below address the most common problems associated with water and moisture in crawl spaces. There are other problems that may occur as well, but overwhelmingly these simple steps will reduce your chances of water infiltration down to a trickle (pun intended).
Rule number One. Prevent or minimize water from getting into your crawl space.
Water in your crawl space is a big problem. Once it gets in there it is really, really bad. Mother Nature causes the moisture to migrate into your living area. Ok, so you are probably asking; “Where does this water come from?” Here is the answer.
Landscaping
Over 80 percent of all the crawl spaces I have inspected have a water infiltration problem caused by the gardener. The planting beds are typically above the soil level that is in the crawl space under the home. Since water also follows the gravity rule, it tends to go down and into the crawl space. Stop the water from this source. Some ideas include drains, drip water systems and shorter water times.
Soil
Another annoying source of water comes from the water table in the soil itself. One can put plastic sheathing over the all the exposed soil to slow the movement of moisture from the soil. This is cheap, easy and very effective. It also has the wonderful side effect of making the crawl space cleaner and safer to inspect.
Plumbing
Plumbing and sewer leaks will happen. The key is early detection. This will be covered under rule number three a bit later.
Rule Number Two. Pressurize your living area with respect to the crawl space.
Pressurize the living area in relation to the crawl space. You need the airflow to move into the crawl space from the living area. There are several ways to accomplish this feat, but the cheapest and easiest is to exhaust air (suck) out of the crawl space in a controlled manner.
Close and seal all the vents under your home except for two vents. These openings will have fans attached to them. Install several small fans based on the formula below that exhausts the perfect amount of air under your home out to the exterior environment. These fans are very small and are about the same size as a bathroom exhaust fan.
A good rule of thumb is about one air exchange per hour. In other words you need to exhaust the entire air volume of the crawl space out every hour. The calculation for cubic feet (yes math is still a useful tool despite what your teenager will tell you) is Length times the Width times the Height) divided by 60 minutes equals the total air volume needed. Here is a typical calculation:
L=60 feet. W= 40 feet. H = 2 feet.
L60 x W40 x H2 = 4,800 cubic feet. Divided by 60 = 80 cubic feet of air per minute (CFM).
This means that you need two very small fans that total at least 80 CFM fan to exhaust the air. Most bathroom exhaust fans move about 100 CFM.
Now one factor to remember is that you need to air to be uniformly pulled from the living area into the crawl space. Put two small fans on the opposite side of your foundation and you have created the perfect airflow control system.
There are several options for the fans. They can be tied into the HVAC system so that they run when your air conditioner or heating system is running (the best option), or they could be energized all the time. This size fan uses about the same amount of energy as a 25 watt bulb to give you an idea of energy usage.
Rule Number Three. Monitor the humidity in your crawl space.
The last thing is the easiest of all the steps. Purchase a good quality moisture sensor and install it under your home in the crawl space. Have the device trigger an alarm of some kind when the moisture level is high. Many of these devices can be configured to send you an email warning. This will give you an early alert for water problems.
If you implement all three of these rules or suggestions, you will reduce the impact of everyday moisture infiltration and provide for an early warning system for mechanical failures in plumbing. When you combine both the prevention with the early warning system, your risk of catastrophic damages from moisture infiltration will be greatly reduced.