Expert: Bruce E. Johnson - 4/6/2009

Question
Dear Bruce,

Starting last fall, when it rained very heavily for a long time, lots of water got into the basement through the furnace exhaust pipe.  The exhaust pipe goes to a stone chimney through a hole about one foot from the basement ceiling; the basement ceiling is about the same level as
the ground. The leaked happened four times since last fall;
each time we collected five to ten gallons of water
(by putting buckets below the aluminum exhaust pipe).

Contrary to the opionion of several chimney guys, the water did not come from chimney crow or the above-ground section of the chimney.  We reproduced the phenomenon by spraying water to the ground around the chimney after a second heavy rain. So there must be a crack somewhere in the underground section of the chimney. Then water built up and pour in through the opening on the basement wall.

I don't know the anatomy of my chimney.  The house was built in 1931.The fireplace and the burner use separate flues.  There were no water coming down to the ash pit/clean out door (for the fireplace) near the basement floor.  The furnace exhaust pipe is not directly connected anything--it just goes through the basement wall and stopped. There is
some space below the hole on the wall, but I have not idea whether the empty space goes all the way down to the foundation footing.
(In other words I don't know whether the water built up all the way from the bottom, rose six feet up and then pour in through the hole, or it just first fill up a small empty space before coming in.)

We tried regrading the area around the chimney, but we still had the same problem after a heavy rain in December. The amount of water coming in was somewhat less, but still significant amount.

The complete, by-the-book solution seems to be to dig up at least the chimney (and that side of the foundation), install asphalt felt along the outside wall, and perhaps installing a French drain. That would also be expensive.

What will be chance of success if we dig down say 3 feet around the chimney and put up asphalt/fiberglass felt or PVC liner on the exterior wall?
Is it necessary to do the whole side of the basement wall?
[We don't have water coming in from the ground or from elsewhere on the wall.]

Will appreciate your advice.

Yours,
Ching

Answer
Hi Ching, I answer probably five questions a week regarding foundations leaking and the answer is always, yes you need a foundation drain.  How serious you want to get about it is up to you but a good footing drain is an important part of a foundation's health.  Water building up against a foundation wall can cause it to fail. It's probably a good thing that your fireplace is leaking or all that water would be pushing against your foundation.  It has to go somewhere.  By providing a way for the water to be diverted around the building and away from it.  While you have the foundation exposed it should be waterproofed with a good mastic foundation waterproofing tar.  Filter cloth laid at the bottom of the ditch, 6" perforated pipe laid in a gravel or crushed rock bed, filter cloth laid over that and then backfilled.  I hope this information helps feel free to write again regarding this or other matters, sincerely bruce e johnson..bejohnsonconsulting.com