Basement waterproofing
Encyclopedia
Basement Waterproofing refers to techniques used to prevent water
from entering the basement
of a house or other building. Effective below ground waterproofing will include both drainage and sealers.
Waterproofing is needed anytime a structure is built at ground level or below ground. Waterproofing and drainage considerations are especially needed in cases where ground water is likely to build up in the soil and raise the water table
. This higher water table causes hydrostatic pressure to be exerted underneath basement floors and against basement walls. Hydrostatic pressure forces water in through cracks in foundation walls, through openings caused by expansion and contraction of the footing-foundation wall joint and up through floor cracks. Hydrostatic pressure can cause major structural damage to foundation walls and is likely to contribute to mold, decay and other moisture related problems.
In masonry foundations, interior sealers will not provide permanent protection from water infiltration where hydrostatic pressure is present. Interior sealers are good for preventing high atmospheric humidity inside the basement, from absorbing into the porous masonry and to prevent spalling. Spalling is a condition where constant high humidity or moisture break down masonry surfaces causing deterioration and shedding of the concrete surfaces.
When the foundation is constructed of concrete blocks, an interior drain tile system, described below, can capture the water entering the block system and drain the water into a sump. Typically, weep holes are drilled into the lowest course of block, allowing the drainage to occur. This system will provide a dry and moisture free basement for years to come.
, it is a widely accepted technique in mitigating basement water and is generally referred to as a basement waterproofing solution. Many interior drainage systems are patented as well as recognized by B.O.C.A (Building Officials and Code Administrators)as being effective in controlling basement water. They function by draining underground water from alongside the foundation footers and underneath the basement floor. They then channel it with a French drain
, PVC pipe, or through a patented product to a sump pump
system, which will then pump the water from the basement
. Foundation sump pumps can be installed through do-it-yourself kits, plumber installations, or by a professional waterproofing contractor and generally come in plastic and cast-iron models.
To simplify:
Interior basement waterproofing systems should be prepared to work in the case of a power outage, the failure of a sump pump, and in the face of overwhelming torrential rain. A proper sump pump, backup sump and/or battery backup sump pump should be installed in a large sump pit with an airtight lid for safety and to keep humidity from seeping through to the basement environment, where it can promote mold growth. This airtight practice will also reduce the possibility of dangerous radon gases for entering the living space.
-based covering.
-based waterproofing products have been developed. Polymer-based products last for the lifetime
of the building, and are not affected by soil pH. Polymer-based waterproofing materials have the advantage of a low enough viscosity
that they can be sprayed directly onto a wall, are very fast curing, and are semi-flexible, allowing for some movement of the substrate.
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
from entering the basement
Basement
__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
of a house or other building. Effective below ground waterproofing will include both drainage and sealers.
Waterproofing is needed anytime a structure is built at ground level or below ground. Waterproofing and drainage considerations are especially needed in cases where ground water is likely to build up in the soil and raise the water table
Water table
The water table is the level at which the submarine pressure is far from atmospheric pressure. It may be conveniently visualized as the 'surface' of the subsurface materials that are saturated with groundwater in a given vicinity. However, saturated conditions may extend above the water table as...
. This higher water table causes hydrostatic pressure to be exerted underneath basement floors and against basement walls. Hydrostatic pressure forces water in through cracks in foundation walls, through openings caused by expansion and contraction of the footing-foundation wall joint and up through floor cracks. Hydrostatic pressure can cause major structural damage to foundation walls and is likely to contribute to mold, decay and other moisture related problems.
Methods
The three measures developed to prevent this problem differ greatly in ideology and design.- The first being interior wall and floor sealers.
- The other two methods are
- interior water drainage and
- exterior drainage combined with waterproofingWaterproofingWaterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...
coatings.
Interior Sealants
In poured concrete foundations, cracks and pipe penetrations are the most common entry points for seepage. These openings can be readily sealed from the interior. Epoxies or urethanes are pressure injected into the openings, penetrating the foundation through to the exterior, thereby cutting of the path of the seepage. These repairs will last for a long time. Many contractors provide 10 year to lifetime warranties on these repairs.In masonry foundations, interior sealers will not provide permanent protection from water infiltration where hydrostatic pressure is present. Interior sealers are good for preventing high atmospheric humidity inside the basement, from absorbing into the porous masonry and to prevent spalling. Spalling is a condition where constant high humidity or moisture break down masonry surfaces causing deterioration and shedding of the concrete surfaces.
When the foundation is constructed of concrete blocks, an interior drain tile system, described below, can capture the water entering the block system and drain the water into a sump. Typically, weep holes are drilled into the lowest course of block, allowing the drainage to occur. This system will provide a dry and moisture free basement for years to come.
Interior water drainage
Although interior water drainage is not technically waterproofingWaterproofing
Waterproof or water-resistant describes objects relatively unaffected by water or resisting the ingress of water under specified conditions. Such items may be used in wet environments or under water to specified depths...
, it is a widely accepted technique in mitigating basement water and is generally referred to as a basement waterproofing solution. Many interior drainage systems are patented as well as recognized by B.O.C.A (Building Officials and Code Administrators)as being effective in controlling basement water. They function by draining underground water from alongside the foundation footers and underneath the basement floor. They then channel it with a French drain
French drain
A French drain, blind drain, rubble drain, rock drain, drain tile, perimeter drain, land drain or French ditch is a trench covered with gravel or rock that redirects surface and groundwater away from an area...
, PVC pipe, or through a patented product to a sump pump
Sump pump
A sump pump is a pump used to remove water that has accumulated in a water collecting sump basin, commonly found in the basement of homes. The water may enter via the perimeter drains of a basement waterproofing system, funneling into the basin or because of rain or natural ground water, if the...
system, which will then pump the water from the basement
Basement
__FORCETOC__A basement is one or more floors of a building that are either completely or partially below the ground floor. Basements are typically used as a utility space for a building where such items as the furnace, water heater, breaker panel or fuse box, car park, and air-conditioning system...
. Foundation sump pumps can be installed through do-it-yourself kits, plumber installations, or by a professional waterproofing contractor and generally come in plastic and cast-iron models.
To simplify:
- Water enters the home via the basement wall/floor joint, through cracks in the foundation walls and/or holes created by faulty or decaying masonry/brick.
- A perimeter trench drain such as a French drain collects the water before it enters into the basement.
- Wall vapor barriers/retarders and drip moldings are used and incorporated into the sub-slab perimeter drain to collect water coming from wall cracks and other foundation wall defects, such as pipe protrusions.
- The drain directs the water to a sump pump.
- The sump pump directs the water out of the house.
Interior basement waterproofing systems should be prepared to work in the case of a power outage, the failure of a sump pump, and in the face of overwhelming torrential rain. A proper sump pump, backup sump and/or battery backup sump pump should be installed in a large sump pit with an airtight lid for safety and to keep humidity from seeping through to the basement environment, where it can promote mold growth. This airtight practice will also reduce the possibility of dangerous radon gases for entering the living space.
Exterior Waterproofing
Exterior waterproofing prevents water from entering foundation walls therefore preventing the wicking and molding of building materials. Waterproofing a structure from the exterior is the only method the IBC (International Building Code) recognizes as adequate to prevent structural damage caused by water intrusion. Prior to the 1980s much of the original exterior waterproofing was actually damp-proofing using a degradable asphaltAsphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
-based covering.
Polymer based compounds
Over the past ten years, polymerPolymer
A polymer is a large molecule composed of repeating structural units. These subunits are typically connected by covalent chemical bonds...
-based waterproofing products have been developed. Polymer-based products last for the lifetime
Lifetime
Lifetime may refer to:*Life expectancy, the length of time a person is expected to remain alive*Mean lifetime, a certain number that characterizes the rate of reduction of a particle of an assembly...
of the building, and are not affected by soil pH. Polymer-based waterproofing materials have the advantage of a low enough viscosity
Viscosity
Viscosity is a measure of the resistance of a fluid which is being deformed by either shear or tensile stress. In everyday terms , viscosity is "thickness" or "internal friction". Thus, water is "thin", having a lower viscosity, while honey is "thick", having a higher viscosity...
that they can be sprayed directly onto a wall, are very fast curing, and are semi-flexible, allowing for some movement of the substrate.