Wisconsin Historical Society

Guide or Instruction

How to Prevent Water Damage to Your Historic House or Building Foundation

Prevent Water Damage to Historic House or Building Foundation | Wisconsin Historical Society

Moisture is the biggest enemy of your historic house or building. Excessive water around your foundation could create a major structural problem with a significant repair cost. However, most water-related house or building problems can be prevented by maintaining your foundation and managing the water flow around it.

Identify Water-Related Foundation Problems

You can determine if your foundation is taking in water by looking for these two signs:

  • Water stains on masonry walls or concrete floors. If you see water stains on your masonry walls or concrete floors, observe your foundation walls during a heavy rain to see where the water is seeping in. This observation will direct you to the areas outside that need drainage improvements.
  • Bowing or sagging foundation walls. A bowed or sagging foundation wall is another sign that excessive moisture migrating into your foundation. Your foundation wall could be bowing inward for several reasons. The most common cause is massive water buildup on the outside of the wall, which creates hydrostatic pressure. This pressurized water pushes the foundation wall inward. Occasionally a foundation wall bows inward due to a large tree root. The root does not need to be pressing against your foundation to cause it to bow inward. A very large tree root 20 feet away from your foundation can shift the earth as it grows. This in turn pushes the ground between the root and your foundation, causing excessive pressure against your foundation wall.

Manage Water Flow Around Your Foundation

The key to preventing water damage is to manage the water flow around your foundation. Here are some ways to keep water away from your foundation:

  • EnlargeItalianate house

    An 1860's Italianate house with a nicely pitched grade around the foundation. Source: Bob Yapp

    Provide an adequate ground pitch. Be sure the ground around your foundation is graded at a pitch of no less than 5 degrees. Any less of a pitch away from the foundation can allow heavy rains, snow melt or roof runoff to saturate the ground and erode mortar joints, bow walls or cause the support footing under your foundation wall to sink.
  • EnlargeHouse gutter

    Cleaning out your gutters will allow the water to be directed through the downspouts and away from the foundation. Full gutters direct the water over the side and directly into the ground adjacent to the foundation wall. Source: Bob Yapp

    Clean and repair your gutters. Be sure your gutters are not sagging and are cleaned out twice a year. Debris-filled or sagging gutters allow roof water to either miss the gutter or overflow. When this happens, the roof water is not being directed away from the foundation through the downspouts and ground extenders. Make sure the gutter downspouts are clear and have ground extenders that move the roof water at least six feet away from the foundation.
  • Cover your window wells. Install clear plastic window well covers to stop rain from filling up your window wells.
  • Avoid installing concrete or asphalt next to your foundation. Water tends to follow these hard surfaces, so don’t install them near your foundation. Sidewalks should be at least 4 feet away from your foundation.
  • Keep plantings at least three feet away from your foundation. Plants attract groundwater, so you should not locate any plants that need to be watered right next to your foundation.

Install a Drain Tile System

Sometimes your efforts to manage water flow around your foundation still fail to stop the water from migrating into your basement. If this is the case, you should consult a foundation specialist to consider one of the following drainage solutions:

  • EnlargeSump pump

    A sump pump located in a basement floor pit will re-direct water away from your basement. Source: Bob Yapp

    Install an interior French drain tile system and sump pump. To install a French drain, your foundation specialist team will cut a channel into the concrete floor around the entire perimeter of your foundation wall. Then the team will dig a trench down to the frostline footing at the bottom of your foundation. Plastic tiling will be installed and attached to a sump pump inside a pit. The water will flow through the wall, into the plastic tiling pipe and on to the sump pump. The water in the sump pit will be drained to the outside and away from your foundation.
  • Install an exterior perimeter drain tile system. To install an exterior perimeter drain tile system, your foundation specialist team will dig a trench around the entire exterior of your foundation down to the frostline footings that support your foundation. The team will then install drain tile piping in the trench next to your footings. The piping will be channeled either to an interior sump pump or away from your foundation and out the side of a hill, retaining wall or a pit in your yard. The trench is then filled in and allowed to settle. After the trench settles, your foundation specialist might need to add dirt to create a 5-degree pitch away from your foundation.
  • Install a clay cap. Your foundation specialist can install a clay cap to divert water horizontally away from your house or building. When rain or roof runoff hits the ground, it soaks vertically through the top foot of grass and soil. However, water does not flow well through clay. Your foundation specialist will install a clay cap, four to six inches thick, about a foot below your finished grade to pitch the water away at least three feet from your foundation. This is a very common construction method when a building has no gutters, because it diverts all the roof water that hits the ground away from the building.