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Two Letters Re: Advice on Enhancing Cool Basement Food Storage
James:
For those looking to create stable and “passively” cool
storage in a basement, the book "How
and Why to Build a Wine Cellar" by Richard Gold is a well-thought, meticulously engineered
solution to many of the same issues faced by those seeking to store
food at
stable, cool temperatures. Regards, - Ben
JWR:
I have spent much of my adult life in the construction industry and
through experience and educational seminars, etc. I have acquired a
substantial amount of knowledge concerning moisture intrusion into
structures.
Water is the main source of problems in construction. Keeping it in,
keeping it out, and getting it out once it is in.
The components of a building that are constructed of concrete such
as basements, foundations and slabs on grade are very susceptible to
moisture intrusion. Concrete acts as a wick and when dry will actually
attract moisture and move it through out the structure under the right
conditions. For example a twenty-inch concrete column sealed on its
sides and standing in water will wick moisture hundreds of feet straight
up. A concrete basement floor set over a wet subsurface will continuously
wick that moisture up through the floor and allow it to evaporate into
the basement atmosphere, i.e., damp basement. For several hundred years
this condition has been referred to as "rising damp". The
modern term for it is capillary action.
To construct a dry basement in damp ground conditions requires some
planning and a little ingenuity. Choose as dry and well-drained location
as possible to build the structure. Once the excavation of the basement
is complete you should proceed with water management measures as dictated
by the conditions of your location. If you have a substantial amount
of groundwater or springs under the excavation you will need to install
a drain system around the outside of the foundation and under the floor
to move this water away from the basement. There is a lot of information
available on how to do this. If located in a hillside it is easy to
install a gravity flow system, dumping into a dry well down hill from
the basement. The only other alternative is to dump into a sump pump
installed in the floor of the basement and pump the water out away
from the house.
Now comes the important part. Once the drain system is completed and
the forms for the foundation and floor have been constructed you will
want to lay down heavy-duty plastic vapor barrier on the ground under
all areas where you will pour concrete. The barrier should cover the
entire floor, pass under the foundation and up the outside wall as
continuous as possible. Where you need to make seams, overlap the barrier
at least five feet. Applying a sealant between the layers at the seams
is advisable. The concrete will be poured over the vapor barrier only
after it has been completely sealed from the outside of one wall to
the outside of the opposite wall. Once the foundation and slab are
poured and the outside walls are constructed, the vapor barrier protruding
out from under the foundation is pulled up on the wall and adhered
using the standard basement wall sealant. The entire outside of the
wall is then coated with sealant. You should end up with basement that
is totally encapsulated in a plastic vapor barrier. Most builders
that attempt installation of vapor barriers ignore the foundation because
it takes a little finesse to do this right. This leaves a path for
capillary action to bring moisture into the basement.
Now that you have a dry basement don't forget to
properly ventilate it. It should be tied in with the rest of the house
ventilation system. If you construct a safe room in one corner it will
still be necessary to supply some ventilation to that room or it will
become very musty.
I am presently planning the construction of a small house for my wife
and I and will construct a safe/storage room as an extension of the
basement, which will extend out from under the house. It will basically
be an underground concrete room next to the house joining the basement
wall and will be totally sealed from moisture as I have described.
I will be able to easily hide the entrance through the basement wall
in the back of a utility room. Being outside of the house footprint
will also protect it from fire in case the house would burn down or
otherwise be destroyed.
Hope you find this useful, - JR
