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How to find source for a leak in my wall

We discovered we have a leak because the carpeting became wet and discolored, while spreading. Pulling back the carpet, the padding was wet and the tacking strip to hold down the carpet was dark and saturated. Pulling back the floor board, we discovered a 12 inch area also dark and wet. We have a problem, but we don't know how to find the source. Could it be coming from a window on 2nd floor, but not directly above? (there is NO window directly above)

No sprinkler system. We use soaker hose and it is on a timer (conservative water users). We live in a DRY, arid state, and we don't plant close to house.

Re: How to find source for a leak in my wall

Could you provide more info. Yes, an upstairs window doesn't have to be directly above to cause a leak---but check out other possibilities as well.

From your description the leak is on the first floor against an exterior wall in a house that has a second floor???--is there an attic above the ceiling; is the leak at the edge of room, near an exterior wall, or interior wall???

Do you have forced hot water heat with radiators/baseboard??? Can you see any water supply piping in the ceiling's edge, just above the leaking spot on the floor? Do you have a fire prevention sprinkler system in the ceiling??

Have you had any recent rains??

Do you have any cellar access directly under the floor leak??? If so, can you see any pipes going to the location of the leak???

Does the interior floor where the leak is, sit (situated) ABOVE the exterior outside walkway, or even with it???----if the exterior walkway is at or above the inside floor where the leak is, any leak in the concrete/brick/asphalt walkway would allow any rainwater or runoff to flow down toward the building wall.

Do you have a one-story house, where you can get a ladder & check the upper exterior wall to see if there is any damage to the roof gutters, or any damage to the first row of shingles, if the leak is located near the exterior wall.

Does the water leak seem to be more pronounced during or after a rain, or is it there constantly?

Re: How to find source for a leak in my wall

If you are on a slab, a leak under the carpet can be caused by a pipe under the slab.

There are plumbers who provide slab a leak detection service - money well spent to stop all guessing games.

Re: How to find source for a leak in my wall

Thank you for responding. Facts: moisture in about 18" of baseboard (measured 50% on moisture meter) exterior wall. Measured moisture ends 4 " from floor, just above baseboard area. Two-story house, but sloping roof (vaulted ceiling) above that baseboard (no room on 2nd floor). Husband went under crawl space and found the wood in that area had moisture damage, but no pipes, no cracks, etc. Thought a leak from a window in an upstairs room adjacent to this area may have traveled down that wall, but homeowner insurance inspector found 0% moisture on wall. He is equally puzzled. We live in Idaho... very dry climate. Could moisture come in from under siding somehow, though. Only sprinkler is a flat hose that husband sprays once weekly. Hits the siding but should just run down.

Such a puzzle! Would love Ask This Old House to visit and solve this problem for us. I sent them pictures.

Re: How to find source for a leak in my wall

So many possibilities but they all boil down to one word, flashing.

Need the following details


siding 8' tall with more siding above?

end wall or side wall?

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