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Source: NHPA

This summer’s high temperatures and humidity further exposed the moisture problems old home owners face in New Hampshire. A group of 15 home owners gathered at workshop presenter George Malette’s 1880 home in Weare, NH for the New Hampshire Preservation Alliance’s Moisture Management Workshop. Malette used the techniques employed in his house, basement, and yard as teaching tools, explaining methods with a powerpoint presentation and guided tour. Since each house and situation is unique, no “single method” exists for controlling moisture in old homes. Home owners must first assess where the water/moisture is coming from, and then choose the best approach to manage it. Thus, Malett’s goal is for home owner’s to minimize the moisture coming into or created in the home, and then control the relative humidity at healthy levels.

Some recommendations:

Outside the home:

  • Keep water out of basement or crawlspace by controlling slope so that runoff is directed away from house (minimum 5% slope)
  • Divert groundwater away from house to a control spot (pond, stream, dry well)
  • Properly mortar exterior of stone foundation (go into ground at least 18″)

Inside the home:

  • Install a dehumidifier in the basement to help maintain the desired humidity level. Keep basement at 50% relative humidity in winter and 55% relative humidity in summer
  • Monitor moisture in home with a relative humidity guage
  • Set up a sump pump; use a sealed basin not an open pit to collect water below level of slab
  • Cover dirt floor with 6ml plastic vapor barrier.

Malette stressed that single details make the difference between a home working and not working. Participaants left the workshop with the knowledge needed to keep outside water out, control moisture at its source, control the basement and the home’s relative humidity and develop a back-up plan (sump pump) if the passive systems do not work. While managing moisture can be a challenging task, by undertaking these approaches, your historic home will be more comfortable, more durable and healthier to live in.