Bare crawl space creates humidity problem

Q. We live in a house that is more than 100 years old. The cellar under most of the house is laid-up stone with a poured cement floor over most of it. Two rooms in the house are over a very narrow crawl space (too narrow to fit a human) that is also laid-up stone but separated from the rest of the cellar by a stone wall.

The two rooms over the crawl space are damp (leather and wood gets white mold on them). According to a handheld monitor, the humidity ranges from 50 percent to 70 percent - often slightly higher than the rest of the house. It is very difficult to access the space under these two rooms. Do you have a suggestion to address this moisture? I think it is contributing to some kind of allergy I am suffering.

A. Normally, I would be concerned about the floor framing over these two rooms having been exposed for over 100 years to this high level of humidity. But you haven't mention any weakness in the floor, so I am assuming if the floor joists are old timber logs, commonly used in these old houses, they have most likely developed a protective coat of a fuzzy, soft, quarter-inch thick velvet that must not be disturbed and is the reason why these logs are still structurally sound.

I have seen many old houses with such logs, but some were so badly weakened that new floor joists had to be sistered to them.

Even though there is a stone wall between this shallow crawl space and the rest of the cellar, you must have some access to have been able to see what the conditions are.

I also assume that by "laid-up stone," you mean gravel-like stones spread over the ground since the cellar part's "laid-up stones" are covered with concrete. This would make a solution I would have suggested perhaps too difficult to carry out. Nevertheless, here it is in case you are brave enough to undertake it:

Faced with a somewhat similar situation years ago in my son's house, we dug a trench, using my World War II army trench tool, so that we could crawl on our backs and lay plastic on the soil. We started one arm-length from one exterior wall, all the way to the far wall and laid the soil to the opposite side of the trench. We pushed a roll of 6-mil plastic all the way through the crawl space and spread it over the space between the exterior wall and the side of the trench, using a broom.

As we retreated, we filled the trench with the dirt excavated from it and repeated the process an arm-length away, pulling the plastic over until we reached the opposite exterior wall.

At the time, being younger and far more active, this was a fun project for father and son to do together.

I don't know what else to suggest in your situation as long as the floor remains strong. If the time ever comes when some repairs are needed and the flooring needs to be removed to have access, the dirt floor can be covered with plastic.

Anyone with a better suggestion?

Q. My daughter's home has a sump pump that over the years has almost constantly filled with water. All of a sudden it stopped filling with water. One contractor used a camera showing her tree roots in the corrugated drain line. Their estimate to replace 17 feet of corrugated line with PVC pipe (9 feet on one side and 8 feet on the other) is about $9,500.

The second contractor said the sump pump crock has a crack in it and needs to be replaced by breaking up the old concrete crock and replacing it with a new one at a cost of approximately $2,600. How can two contractors have such two different solutions? What is now happening to any water not coming into the sump pump? She is calling another contractor to get a third opinion.

Just checked with my daughter. They are not in a drought area. She noticed no water coming into the sump area via the drain tiles a couple of weeks ago. Water is coming up from the floor of the sump pump crock basin, and the water is pumped out when it reaches the top of the sump. Helpful?

A. I assume you mean that the drain line is actually a foundation drain, which leads into the sump because the lay of the land does not make it possible to discharge it to daylight.

If the tree roots are preventing the filling of the sump, it may indicate that the blockage is at the point where the foundation drain tile enters the house. Otherwise water would come around any blockage from the other side.

Water building up in the drain may be slowly working its way through the root mass and coming into the sump from its bottom instead of through the drain connection.

I suggest that your daughter call another plumbing contractor or Roto-Rooter who should be able to ream out the roots unless they feel that they cannot do it because, as you mention, it is a plastic corrugated pipe that their electric snake would tear up, in which case ask if they could pour into the sump a chemical that would destroy the roots, or find someone else who would. As to the second contractor, I fail to see why a cracked crock would prevent the sump from filling. I don't see any need to replace it.

Q. A recent column in our Chicago area newspaper identified a product you recommend for cleaning and degreasing kitchen cabinets. I accidentally threw the paper away before making a note of the product, which was available for purchase on the internet. I would so appreciate a reply with this information. Thank you!

A. The magic product is Milsek. You can find out more information and select the product that suits your needs best on their website: www.milsek.com. Click on "Where to Buy," enter your ZIP code to find out if Milsek is available locally or order it online by clicking on your chosen product.

A great suggestion from a reader: "I enjoy reading your column every week. I think you missed for the person who is trying to install a microwave without a cabinet to attach it. I had a similar situation and just installed a shelf above the microwave and hung the microwave from it. Keep up the good work."

A. Brilliant! Thank you. Such a simple solution! Wish I had thought of it.

• 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.