I have had two water leaks caused by copper piping freezing and bursting in an exterior wall where it comes through the concrete foundation to an exterior hose bib, even after the copper pipe running between the studs has been insulated. Plumber stated the pipe is located too near the edge of the concrete foundation and suggested either chipping away at the foundation or somehow insulating the foundation. Would a box built outside the foundation and filled with insulating foam accomplish the purpose of preventing freezing, and if so how large would such a box need to be?

  • 3
    A shut off valve on the inside will help more. Turn on the outside hose bib and turn off the inside valve before freezing.
    – crip659
    Jan 25 at 23:56
  • What's the measurement from the concrete foundation's exterior surface back to a heated area? It's the interior of the house back there? Not a below freezing crawl space?
    – popham
    Jan 26 at 5:37
  • It is an unheated area underneath the stairs; there would be no access to the pipe from inside the house. As far as I know the foundations is solid and the 2x4 exterior wall is flush with the edge; making the pipe about 3 inches from the foundation under the stairs and about 6 feet from foundation uder a heated space.
    – user181711
    Jan 27 at 0:45

2 Answers 2


There are standard ways of dealing with this, and they involve draining the pipe in freezing weather, one way or another. A concrete foundation exposed to the cold will freeze, and any pipe inside it will freeze as well. Insulation might slow that down, but it won't stop it. Removing the water lets the pipe freeze without it causing a problem or bursting.

Simplest is a "frostproof sill cock" which is a LONG valve body with a long valve stem so that the actual operating part of the valve is all the way inside the house. They come 8, 10, 12, 16" long - the hose connection and handle are outside the house, the valve is inside the house. You do need to remove the hose from the connection in freezing weather so the part of the sillcock inside the wall can drain. They work, if the part of the house where the valve is located is warm enough, and the hose is removed.

The other method is a shutoff valve inside the house and remembering to shut that off and open/drain the outside valve and connecting pipe before freezing weather. Typically the inside valve is one that has a cap for the downstream side so that you can open that cap when draining the line.

  • My inside valve doesn't have a vent cap, but I've found that if I open the hose bib just the right amount surface tension helps draw the water out to empty it. So far, so good, after 15 years in the house..
    – keshlam
    Feb 25 at 14:38

Without any location information it's impossible to give accurate guidance. However, just insulating the outside of the foundation won't, in itself, likely solve your problem. You need to not only insulate it from the outside, but also need to make sure that there's sufficient warmth (either from the ground, or inside source) to keep it from freezing. Insulation isn't a magical "stop the cold completely" type of material. It slows thermal transfer down, but eventually the temperatures on either side of the insulation will equalize in absence of a source of temperature differential on one side or the other.

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