These days, most residential foundations are constructed of poured concrete because the monolithic foundation has become the accepted standard in most parts of the country and because ready-mix concrete is widely available.
In some parts of the country, masonry foundations constructed of concrete block are still being used, due either to custom and practice or to distance from ready-mix concrete plants. Of course, further back in history before concrete could be trucked to a building site, masonry foundations were built of locally available materials like stone and brick.
Both foundations are long-lasting and structurally sound but each is prone to cracking caused by lateral pressure from over-saturated soil or desiccation of the soil below the foundation that causes it to drop or sink.
Depending on the severity of pressure or movement, either a structural or non-structural crack can occur. Structural cracks are a sign of serious damage or destabilization of the foundation and repair methods address the foundation in total, not just cracks. Repairs are extensive and can be costly.
Non-structural cracks, although they are not as damaging, do allow water to enter the basement and can cause damage to furnishings or stored goods and can lead to mold and high humidity in the home.
Non-structural cracks are common in masonry foundations and occur in the mortar joints between blocks, stones, bricks, tiles or whatever masonry unit is used in the construction. Most homeowners understand that this is a problem that must be repaired by waterproofing professionals and many of them are concerned about the cost.
There are two ways to handle seeping cracks in a masonry foundation – manage them from the interior or repair them permanently from the exterior.
The interior approach begins with installing a system of interior drain tile that can range from one damaged wall to an entire perimeter installation. Interior drain tile, used to alleviate hydrostatic pressure, is a system of perforated pipe that is buried in a bed of washed gravel next to the foundation footings below the basement floor. The drain tile is connected to a sump pump and it collects groundwater and delivers it to the sump pump for disposal.
When the portion of floor that had been removed for installation is replaced, a small gap is retained between floor and wall so that the seepage can trickle down the wall and flow into the drain tile system. Although not required, it is recommended to install a vapor barrier over the wall to hide the seepage and contain moisture.
The cost of installing drain tile depends on the linear footage of pipe to be installed but will be at least several thousand dollars. The cost of vapor barrier installation is determined by the lineal foot and will cost several thousand dollars, depending on how many walls are covered..
Fixing a crack from the outside on a masonry foundation begins with excavating along the affected wall down to the footings. If the foundation wall is made of stone or rough brick, a parge coat of mortar is first applied to the wall. Next, a thick coating of asphalt-modified polyurethane is troweled onto the wall to create an exterior waterproofing membrane, a permanent barrier against water entry.
If ground water is high, the membrane can be supplemented with exterior drain tile and heavy-duty drainage board to protect the membrane and channel water down to the drain tile. The excavation then backfilled and the repair is complete.
This exterior repair involving excavation and backfill and as many as two coating steps can cost multiple thousands of dollars and can be roughly estimated as two to five times the cost of a comparable interior repair.
Any homeowner with seeping cracks in a masonry foundation will require the advice and assistance of a professional basement waterproofing contractor. At U.S. Waterproofing, we have been fixing masonry foundations all over Chicagoland, southeast Wisconsin and Northwest Indiana since 1957 and have a list of more than 300,000 satisfied customers to attest to our service. Why not ask for our free advice?
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