Much of the information contained in this section of Anatomy of a
Home was written from materials, and its use is approved of, by
Larry Janesky, author and President of
Basement
Systems Inc., and his staff, of Seymour, CT. Inquiring Eye Home
Inspections, LLC is grateful for their generous support.
For those of you who are old enough, do you remember referring to
your basement as a cellar? Here in Connecticut, the use of the word
“cellar” refers to wine cellars or to some farmers and naturalists
who may still maintain a root cellar. But before the days of
mechanical refrigeration, a family’s food supply was stored, in many
instances, in the area below the ground level of the house in a
“cellar”. This is because the soil temperature a few feet down
maintains a year- round constant temperature of approximately 55
degrees in Connecticut. Our forefathers would can fruits and
vegetables, cure meats and fish by salting or smoking them, and
store them along with fruits and vegetables for consumption in the
year to come. For thousands of years ice has been harvested from
surrounding ponds and lakes in winter and wrapped in sawdust,
seaweed, or straw to slow the melting process. This ice would then
be used to “refrigerate” food. The most common cause of early
famines resulted from a farmers’ inability to store enough food to
last from one harvest to the next. This is why fall festivals,
county fairs, or our Thanksgiving were so important to earlier
societies. In times of a good harvest they wanted to give thanks or
celebrate.
But the need to feed standing armies, or years of poor harvests, or
warm winters with little ice brought on the need for a better, more
permanent, method of storing food. The early 1800’s saw the
invention of the icebox, and then the introduction of the first
mechanical refrigerators, in 1911, by General Electric. Today the
refrigerator is the most commonly found household appliance. With
the advent of the refrigerator came less of a need to store foods
for such long periods of time and thus, the end of the cellar, by
the average American. So, the cellar gave way to the basement. The
basement and the crawl space are where the boiler or furnace is most
commonly found. But more and more, homeowners want to utilize every
possible square inch as a living space. Houses built today, in most
parts of the United States, have higher basement ceiling heights and
pipes and electrical wiring are recessed so the basement area can be
finished into a usable space. With this increased need to finish a
basement space also creates the need to protect these finished areas
and possessions from water entry from the ground soils on the
opposite side of the foundation wall, and the mold and air problems
that may be a subsequent result of this problem.
No matter whether your basement is finished or not, the moisture and
air problems that start in a basement or crawl space can affect the
air you breathe at the other levels of the house. As this warm air
rises throughout the house, it carries with it the radon, mold and
allergens and other issues that started in the lowest portion of the
house.
Stack Effect
This warm air rising upward through
the various levels of a house is called the “stack effect.” Building
scientists believe that 50% of the air we breathe on the first floor
of a house is derived from the building level in direct contact with
the soil. Therefore it is important to correct the mold, allergens,
and high humidity at there source before they become an issue
elsewhere.
In basements or crawl spaces, “negative” air pressure can introduce
moisture into the lower level of a house, and this moisture creates
an environment for the creation of mold and allergens. Negative
pressure is created because the stack effect in the house is pulling
air upwards, which creates a lower atmospheric pressure in the
basement or crawl space. Mold needs high humidity, proper
temperatures, and a food source to be created. Janesky writes, that
this humidity is created “whenever the outside air is warmer than
the inside air, and especially when it’s humid outside air, we are
likely to have a condensation problem in subterranean levels….The
relative humidity, how much moisture the air holds, goes up 2.2% for
every one-degree you cool it. Our basements are always cool because
they are below ground… As the air becomes saturated it gives up its
moisture on your cold basement walls, floor, water tank, cold water
supply pipes and other cold things. This is called condensation.” We
have all seen water droplets forming from our house’s cold water
supply lines, or a well pressure tank. This is evidence of warm,
humid air condensing on the inside cooler portions of the house.
Learn about:
basement waterproofing and
crawl space vapor barrier
Foundations
Depending on when the house was built can determine what method of
water treatment for the exterior of the foundation was used, if any,
by the contractor. Until 1985, the most common method was to seal
the exterior of the foundation walls with a tar coating called “damp
proofing.” Historically, damp proofing has not sealed the foundation
walls completely and does not bridge cracks that may occur in the
foundation, due to settlement. Settlement cracks are a very common
occurrence and are present at most houses. More recently, a
“waterproof” coating may have been applied. The problem with both of
these methods of foundation sealing is that they will both
deteriorate with time.
Again, depending on when the house was constructed, you may also
have a footing drain (refer to Anatomy of a Home, Foundations).
Footing drains are perforated plastic pipes that are placed in a bed
of gravel and are designed to drain the ground soil moisture present
at the home’s foundation. They are called “footing drains” because
they are located at the base of a foundation wall where the house
footing and foundation meet. A problem with a footing drain is where
does the ground soil moisture drain too if the surrounding property
is fairly level? Building codes may require a footing drain to be
present and if its presence is the only thing that the town building
official is concerned about, what good is it? The official is more
likely than not concerned about where this water is being deposited.
Secondly, over time surrounding ground soil may eventually clog the
pipe by leaching through the gravel bed that the pipe is imbedded in
and make it meaningless. Larry Janesky writes, “footing drain
failure is the most common cause of wet basements.”
The grading of the
ground soils at a home’s foundation and the depositing of roof
drainage from gutters are also great contributors for water entry
into a basement or crawl space. When it rains and the soils are
pitched towards the house, or the downspouts deposit at a foundation
corner all that water is deposited against the house foundation. A
gallon of water weighs approximately 8.5 lbs. With the weight of all
those pounds of water against the foundation, called Hydrostatic
Pressure, it is inevitable that water will eventually leak through
the foundation. Concrete is porous, and that there are joints
between the foundation, the footing, and the basement floor. If your
house is constructed from a hollow concrete block, or cinder block
or stone, think of how many joints you have, and that the center of
the blocks are hollow.
A solution is to make sure the soils at the foundation are pitched
away from the house (½ inch rise, per foot of run) by a good six to
ten feet. When additional soil is added a good four to six inch
space should be left from the soil to the exterior siding. Don’t
create termite or carpenter ant issues while trying to solve water
issues. Downspouts should extend as far away from the house as is
feasible, or deposit into a buried pipe that moves the water away
from the house and drains in the yard. The vast majority of basement
water issues can be resolved by simply pitching the ground soils
away from the house and cleaning and maintaining gutter systems and
depositing this water as far away from the house as possible.
Cracks in basement walls are very common, and are present at most
homes. The cracks can mean different things depending on what kind
of material the foundation is made of, or the cracks size, and
location. The majority of the cracks fall into two different
categories, construction related or soil related.
Construction related issues:
Poor concrete mix
Rapid concrete curing
Premature removal of the concrete forms
Premature backfilling
Improper backfilling
Plumbing leaks
Soil related issues:
Poor drainage
Hydrostatic water pressure
Clay soils which expand and contract.
Uneven moisture around the foundation
The most common type of
crack, in a concrete foundation, is caused by shrinkage of the
concrete during the curing process, or settlement of the ground
soils directly below the foundation. The cracks will run vertically
or at a slight angle, are hairline, random, and usually develop in
the first year of the house’s construction. Angled cracks appear
when the download and upload offset each other. They can appear when
there is a major difference in the soil under one portion of a house
to another. The most significant issue caused by soil settlement or
curing cracks is water leakage from the exterior. Additional cracks
may appear after a house is remodeled. Clay soils will expand as the
soil absorbs moisture in rainy periods, and shrinks during drier
periods. The expansion of the soil also exerts pressure on the
foundation.
Cracks more than 1/4 –inch wide, cracks with misaligned edges, or
cracks that run horizontally across the foundation are more
significant and should be professionally assessed. Horizontal cracks
indicate pressure being applied from the ground soils and can be
caused by improper, or premature backfilling, or too much water
weight, hydrostatic pressure, against the foundation. The wall will
bow inward, and the surface of the wall will be out of vertical
alignment. The crack is usually wider on the inside face of the
wall. Pilasters (a masonry column built against a foundation wall
which is designed to help absorb the horizontal load and
stiffen/support the wall) may have to be installed to add interior
support to the wall. A pilaster may consist of a column of concrete
blocks or poured concrete designed to help absorb this pressure.
Another form of basement foundation repair can be a helical screw
anchor. A small hole is drilled through the foundation wall. A hole
is dug in the exterior ground soils. A screw anchor is then passed
through the foundation wall and abutting ground soils to the
excavated hole. The exterior anchor is finished, at the ground
soils. A plate is present at the interior foundation wall to help
support and disperse the load and provide support.
A concrete block
foundation shrinks as it cures. An angled crack may appear, most
commonly at the center of the foundation. They occur more in the
center of the foundation because the building is stronger at its
corners. This type of crack is called a step crack. The crack will
follow the line of the concrete blocks.
Stone foundations are most commonly found at homes built from our
country’s founding to the beginning of the early 1900’s. Cracks in
stone foundations are not usually found passing through individual
stones but follow the interlacing of the stones. Cracks and damage
will most commonly occur where the stones have been compromised by
the removal of some stones, changes in the soils at the foundations
exterior, or deteriorating mortar joints caused by the amount of
lime used in the mortar and high humidity levels. If the interior
base of the stone foundation has what appears to be a pile of sand,
running along its base, then you may need to have a mason repoint
the mortar joints. The “sand” is from the deterioration of the
mortar joints.
Another sign of a damp basement is a white powder found on the
basement or crawl space walls. This powder is called efflorescence.
The white powder, or efflorescence, is formed when moisture has been
left standing at the exterior of the foundation. Some of this water
moisture passes through the foundation and picks up salts, lime
and/or other minerals that are present in the foundation building
materials. When this moisture dries, it leaves behind the white
powder residue. Efflorescence can occur at any type of masonry
foundation.
Ventilation
When my wife and I moved back to Connecticut, we purchased a small
Cape. Just like many before us, we moved into our new home with
great pride. But again like many others, we had many boxes of
keepsakes, “memories” ….junk, that we did not know what to do with,
so these memories were “stored” in the basement. But, by the end our
first summer in our new home many of these keepsakes were moldy and
ruined. So what ruined our memories?
We had a mold problem in our basement because the warm humid summer
air from outside our house was warmer than the air in our basement.
Warm air has to expand and is always looking for a colder place to
expand into. This warm humid air sought the cooler basement, and
created a condensation problem. Basements and crawl spaces are below
ground so they are cooled by the surrounding ground soils. When
warmer, humid air, from the outside enters a basement or crawl
space, the Relative Humidity increases 2.2% for every one-degree you
cool it. So, if it is 80 degrees outside, and 66 degrees in a
basement or crawl space you will increase the humidity levels in the
that space by 30.8% (2.2% x 14 the difference in the temperatures).
If we already have a high humidity level existing in the basement or
crawl space then this increased level of humidity will form into
condensation. We have all seen cold water plumbing lines or air
conditioning duct work in a basement dripping with condensation on a
summer’s day. This increase in humidity level created the mold
problem we experienced in our basement. Mold needs a food source,
our junk, warm temperatures, and high humidity levels. As I stated
in the section on mold, the presence of mold is a symptom of a
problem. You must solve the source/problem that allowed the mold to
grow before you can clean up the mold. To eliminate this condition
you can either heat the air or take the water out. In summer, the
best solution is to run a dehumidifier or an air conditioning
system. Both of these reduce the humidity levels and remove the
water content.
Mold
Efflorescence
In crawl spaces, this
high humidity is made worse by having a cold dirt floor. The dirt
will always have moisture present in it, and be cooler. So we are
starting with a bad condition and making it worse. Larry Janesky has
the right theory in mind when he asks, “Why do we ventilate a crawl
space with those little vents?” (Which are required by the Building
Code). In summer, the ventilation that is provided is only allowing
warm moist air to enter, causing it to condense. This condensation
then is absorbed into the wood framing in the house. The wetter the
air gets, the wetter the framing, insulation and mechanicals present
in the crawl space get. The wetter these items get the more
opportunity we are providing for the growth of mold and rotted
framing. In winter, this ventilation is cooling our house and
increasing our heating bills. This high summer moisture level
affects the air we breathe in the house and damages elements of the
living section of the house. This is most evident in hard wood
flooring that has absorbed this moisture and the floors are
“cupping.” So what we do in our basements and crawl spaces does
effect the way we live in our house.
To help relieve this condition it is recommended to at least seal
that crawl space dirt floor with a layer of heavy mil plastic, or
even better put in a concrete or Neutocrete floor. Run a
dehumidifier, AND close those vents!!
Bibliography
1. Janesky, Lawrence, Dry Basement Science, 2005, ISBN:
0-9776457-0-3
2. Janesky, Lawrence, Crawl Space Science, 2006, ISBN: 0-9776457-2-X |
