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Basement leak may require several remedies

Q. Our problem is a leak in our add-on basement. The basement was dug under the existing foundation and footings about 43 years ago. The cement walls were framed 12 to 15 inches deep inside of the footings. The outside of the walls were not framed as the earth was the framing. There are drain tiles laid around the inside floor perimeter emptying into an internal sump pit.

The leak is at the dry seam at the top of where the new wall meets the original foundation, just above the footing. This first happened about 15 years ago. The repair was to chisel out the seam and fill it with hydraulic cement. This fix lasted until now. I think the water is coming underneath the hydraulic cement and leaking onto the ledge of the 12-inch deep wall.

We are able to contain the leak by putting towels on the ledge. However, this is becoming increasingly more difficult. All of the water that is coming in is clear. A crude drawing and photos are attached.

We have tried altering the slope at the back of the house. This is the only place we are having this issue. The soil is as high as we can go against the house without touching the siding. The earth is only in contact with the cement foundation. About 4 feet from the back of the house is a paver walk leading to the paver patio, which is over the area in the basement that is seeping. We have had the pavers reset, sanded and caulked this past summer. Our backyard has crested due to the roots of two large trees. We have oversized gutters and downspouts.

The downspout on the northeast corner empties into 5-inch PVC pipe, leading to drain tile that empties into a french drain almost at the end of our property.

We have had several professionals give us their ideas: Drill holes and inject a substance horizontally into the dry seam, with no guarantee; Dig around the foundation in the back of the house 3 feet wide down to the original footing, tar the foundation and put plastic barrier and back fill, with lifetime guarantee. This concerns me because the packed clay against the house would be disturbed and new spaces would be provided for more water to get closer to the foundation.

We live in a Northwest suburb of Chicago. We are now dealing with melting snow and rain, and fear we will soon not be able to contain the leakage. We sincerely appreciate any ideas you could offer.

A. Thank you for the photos; they are very helpful.

They show flower beds on both the north and east walls of the house with a brick border on the east side. Flat flower beds against a foundation can be a problem because they allow deep drainage of rain and snowmelt. It is best to have a healthy grass stand sloping gently away to allow for natural drainage and evapotranspiration. However, I can see that your yard appears quite flat, which is not helping.

It is important to remember that water reaching the footing can travel considerable distances sideways until it finds a weak spot. In similar situations, I have recommended creating a swale some 6 to 8 feet away from the house and sloping the ground from the foundation to the swale. The yard on the other side of the swale will also have to be altered to form a gentle slope.

Surface water will drain to the swale where it will percolate and evaporate in time, away from the foundation. If the swale can lead water to a lower spot in the yard, so much the better.

An alternate, when there is not enough space between the grade and the siding to raise the grade, and if the house has wide enough overhangs and/or gutters and downspouts, is to set 6-by-6-inch pressure-treated logs 4 inches away from the foundation. Adding new soil against these logs and sloping the yard for 5 to 6 feet will provide adequate drainage. The few inches between the house and the logs allow for the removal of leaves and other debris while keeping soil away from the siding.

The downspout connected to the underground drain at the northeast corner, close to the area where you are experiencing leakage, should be carefully checked. Make sure that it drains properly and does not have a break or a disconnected joint close to the foundation. This may require some digging. Too often these underground drains can be plugged by soil buildup or squirrels and other small critters building nests inside them.

The brick patio, set in sand, appears to be very flat. All water and snowmelt percolating through can reach the original footing where they seek weak spots. It would have been best to set the bricks on a concrete base. Probably far too expensive to redo.

Inside the basement, your sketch shows that the new concrete wall is poured higher than the existing footing and covers its overhang, forming a ledge.

If suggested outside corrections are not successful, and since the seepage is at this joint previously treated with hydraulic cement, it may be necessary to chisel a channel wide enough to apply new hydraulic cement in it.

Q. I follow your newspaper column in the Daily Herald and would appreciate your recommendation for care and cleaning of wood floors. What floor cleaning solution would you recommend?

A. Bona is one of the best, if not the best.

Q. We really enjoy reading your column. Our house was built in 1985. The ceiling has combined insulation of batts and blown in with a combined R factor of R-30.

We want to add more blown-in insulation. You seem to prefer blown-in cellulose rather than fiberglass. Which should we use?

A. I prefer cellulose because it uses recycled paper products whereas the manufacture of fiberglass requires a huge amount of energy.

Cellulose is also denser than fiberglass and has a slightly better R-factor than fiberglass per inch.

Be careful not to block any soffit vents if there are any. Installation of baffles to protect soffit vents may be needed.

• Henri de Marne, a former remodeling contractor turned columnist and consultant, is the author of "About the House with Henri de Marne" (Upper Access Publishing). He continues to take questions from readers for this column and his website, www.henridemarne.com. Email questions to aboutthehouse@gmavt.net.

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