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Leaky Basements Can Be Fixed with Exterior Waterproofing

Mar 18, 2014 • By Matthew Stock.


As winter snows melt or summer thunderstorms pour down rain, telltale signs of home maintenance problems commonly begin to crop up.  Gutters leak, lawns grow puddles and mold begins to sprout.

Worst of all, basements begin to get leaky.  At the end of winter, the soil around the foundation thaws and ground water once again tries to find its way in.  During periods of heavy rain, water runoff finds its way down along foundation walls and discharge from downspouts and overflow from clogged gutters permeates the soil and eventually seeps into the basement.

When the water comes through visible cracks in a poured concrete wall, these leaks can be fixed with the injection of expanding polyurethane.  Basement leaking through floor cracks or the cove joint between wall and floor?  Interior drain tile will fix that.

It’s a different story, however, when the basement leaks in one of these spots:

  • Around water or sewer lines or other utility openings;
  • Over the top of a concrete foundation wall;
  • Through deteriorated mortar joints; or,
  • Patches of porous concrete or porous masonry like concrete block or brick.

Stopping these leaks in a basement requires a different approach that takes place on the exterior of the home to stop water on what’s known as the “positive side” of the foundation wall.

Fixing Leaky Basements with Exterior Waterproofing

Fixing a leaky basement under the conditions above is a fairly simple process but it does require a fair amount of work and preparation.

The first step in exterior waterproofing is to dig.  To be specific, the foundation in the affected area is excavated down to the footings, leaving a space for technicians to work.

Next the installer places clips on the wall to which drainage board will later be attached.  The clips go on first so that they will be sealed onto the wall and not become new sources of seepage.

After the clips are in place, installers apply a thick coat of exterior waterproofing membrane to the wall, which is an asphalt- or bitumen-modified polyurethane compound that completely seals the wall against continued water intrusion.

There is a big difference between the exterior waterproofing membrane and so-called “damp-proofing.”  The exterior waterproofing membrane is applied with a trowel and cures to form a substantial, impervious barrier across the entire affected area of the foundation.  Damp-proofing is a thin coating that is sprayed onto the foundation, usually during construction, which is intended to protect the basement from damp soil, not ground water seepage.

After the membrane has cured, a heavy-duty plastic drainage board is attached to the clips.  The drainage board has a dimpled surface that allows water to drain downward and the board also protects the membrane from the soil.  Filter fabric is usually installed over the drainage board, then insulation can be applied to help the basement stay warmer as well as drier.

In cases where ground water levels are normal, the excavation is then carefully back-filled and the job is complete.  When high ground water is a problem, exterior drain tile is installed in a bed of washed gravel next to the footings.  The drain tile collects ground water and carries it to a sump pump for disposal.

There are many grisly tales of homeowners who tried to do exterior waterproofing on their foundations with off-the-shelf products like roofing tar and plastic wrap, which turned out to be a waste of time and money.  A homeowner with the described seepage issues needs the services of a basement waterproofing contractor that is experienced in doing exterior waterproofing.  At U.S. Waterproofing, we have been keeping basements dry around Chicagoland, outside and inside, for more than 57 years and we have a list of more than 300,000 satisfied customers to show for it.  Why not ask for our free advice?

Tags: leaky basement, leaky basements, leaky basements, exterior waterproofing

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