As houses age, most basements start seeping water through the concrete or
cracks after a heavy rain or snowmelt. The walls, carpets and furniture get
wet and molds start growing in just several days. Moldy drywall, carpeting
and furnishings have to be discarded.

Why to risk your basement remodeling investment (typically $30,000) and more
importantly, the health of your family? Before finishing the basement, seal
it against moisture!
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Basements as a Source of Moisture
Sooner or later, most basements develop water seepage. At first, it is just
intermittent after a heavy storm or snowmelt raises the groundwater level
but over time, the leaks become more and more frequent.

All houses settle and stress cracks may develop in the slabs or the walls.
The floor-to-wall joint opens up and expansion control joints in the floor
crack, as designed. Exterior waterproofing coating deteriorates and the
drainage system may silt up. Hydrostatic pressure then pushes water through
any cracks or right through the concrete.

However, most moisture infiltrates into basements in the form of water
vapor, which is invisible, unlike steam condensing above a pot with boiling
water. Low air pressure inside buildings draws in soil gas with water vapor
from the ground through all openings and pores in the concrete.

Basements are the largest source of moisture in homes and typically, let in
over 15 gallons of moisture each day! That is much more than cooking and
showering combined (3-5 gallons per day).

Concrete is Very Porous
Concrete cures by cement reacting with water (hydration). But concrete mixes
contain much more water than needed, in order to make them easily
³workable.² Almost half of the water is surplus and has to evaporate as
concrete cures. While water pushes through the concrete to the surface, it
leaves behind a network of tiny capillaries (pores), much smaller than a
human hair.

As a result, concrete is more porous than Swiss cheese ­ residential
concrete contains 12 to 20 percent air! Gases and vapor (water molecules)
flow easily through the pores. But liquid water has is tougher ­ the water
molecules are held back in a ³blob² by surface tension until the pore
surface gets wet. Then, liquid water starts seeping through the wet pores in
concrete (capillary seepage). Moreover, the pores draw in water like a
sponge by capillary action ­ water comes up through a concrete slab against
gravity.

Sealing the Sources of Moisture:
Eliminate internal sources of moisture:
*    vent the clothes dryer to the outside
*    insulate air-conditioning ducts against condensation

Keep Rainwater away from the Foundation:
*    proper gutters and downspout extensions
*    properly sloped grading around the foundation
*    shallow swales or French drains to steer rainwater away

Seal All Openings:
*    cover the sump pit airtight
*    tape a plastic sheet to isolate the crawlspace
*    cover airtight the gravel bathroom rough-in
*    install check valves in floor drains to stop vapor
*    seal open cores in block walls with expandable foam
*    similarly, seal hollow lolly (support) columns

Caulk All Gaps:
*    the floor-to-wall joint
*    expansion control joints (straight cuts in the slab)
*    caulk around all penetrations

Fixing Concrete Cracks:
1.    Hydraulic cement is often used for cracks, but it has no ³give² and as
the concrete constantly moves, expands and shrinks, it gets loose and the
crack starts leaking again.
2.    Caulk does not penetrate the full depth of the crack and as water
continues to deteriorate the concrete inside the crack, the caulk tends to
get loose.
3.    You can hire a contractor to inject the crack with epoxy or polymer
foam.
4.    Or purchase a do-it-yourself foundation crack repair kit to seal the
whole crack with low-pressure injection.

However, still does not seal perhaps the largest source of moisture ­ the
concrete itself.

Sealing Concrete against Water and Vapor:
Homeowners often paint walls with a store-bought waterproofing sealer, which
is merely a latex-based paint. Sooner or later, it will crack and peel under
the attack of lime from the concrete (saponification). And it cannot hold
back efflorescence (³whit powder²) or a high negative side water pressure.
More importantly, it is porous and cannot stop water vapor ­ or most of the
moisture seeping through the concrete.

Some cover the concrete with plastic sheets or use plastic covered
insulation ³pillows² on the walls. But this traps any moisture coming
through the concrete and is known for causing severe mold and mildew
problems. We strongly recommend against trapping moisture - all moisture
coming through the concrete should be allowed to evaporate.

Floor slabs are usually poured on a plastic sheet ­ a ³vapor barrier.² But
it gets usually punctured during construction and over the years, it slowly
disintegrates under the attack of lime in the concrete.

To stop water vapor, concrete slabs are sometimes painted with epoxy or
urethane paints, which are impermeable to vapor. They trap all the moisture
for a while, but after several years, the paint starts bubbling or cracking
and loses its purpose.

We strongly recommend sealing the concrete with a top-quality silicate-based
penetrating sealer. It penetrates deep into the pores in concrete, reacts
with lime and alkalis, expands and hardens, which bonds and seals the
concrete permanently!

Seal the Concrete before Finishing the Basement:
Concrete is not a rock! It is porous and it ages, becoming more and more
porous. Just like wood, it needs a sealer - protection against water and
deterioration.

Seal the concrete before finishing the basement, enclosing the walls or
covering the slab, or just painting concrete. It is a simple do-it-yourself
project and avoids putting your basement remodeling investment, as well as
your family¹s health, at risk.

RadonSeal penetrating sealers, available at radonseal.com, seal concrete
not only against water seepage, but also against water vapor and even radon
gas. RadonSeal foundation crack repair kits allow homeowners to fix
foundation cracks like a pro.

Joe Cumpelik, Novion inc.
http://radonseal.com