Home repair: Warm weather brings funky odor

Q. I live in a Northwest suburb of Chicago and have been an avid reader of your column for some time. I have even written for advice before.

For the past few years, my wife and I have noticed a very bad odor in the house on really hot days when we have the air conditioning on. At first, I thought the odor was coming from the central air-conditioning unit or the crawl space. We have a split-level house with an attached garage. Our driveway slopes down toward the garage and requires a sump pump to pump the water from the driveway. I have been able to determine the odor is coming from the sump pump basin in the garage.

I have tried sucking out all the water in the basin, cleaning the basin with a mixture of bleach water and then refilling. The odor just keeps coming back. It is strongest in the foyer near the staircase and the kitchen. The underside of the staircase is in the garage and has some small gaps. I have not tried filling the gaps with anything yet to keep out the odor. So far, the easiest fix seems to be cracking the garage door about 6 inches to let fresh air flow through the garage. I was wondering if you had any other potential solutions?

A. I take it that you do not smell this bad odor during the heating season. I suggest that you seal the small gaps on the underside of the stairs and, if there is a window in the garage, keep it open a couple of inches until the heating season starts. If keeping the window partially open presents a safety concern, screw a wood block in the lower sash track to prevent opening it further.

Time will tell if you have properly determined the source of the odor and if closing the gaps in the stairs has solved the mystery. But consider calling an HVAC contractor to check out the air-conditioning unit in case it is the culprit. These units have been known to collect condensate and cause problems.

Q. I am nearly ready to seal a newly poured driveway and was hoping to receive your advice about which sealant to use. I know that you recommended linseed oil previously, but I seem to recall that you may now prefer another sealant. However, I do not recall whether you have ever stated whether you prefer/recommend silanes, silicates, siliconates or some other chemistry, or if you still stand by the linseed oil as the preferred penetrating sealant. Would you please advise? We have not driven on the driveway since it was poured and won’t until after it has been sealed.

A. A mixture of equal parts boiled linseed oil and mineral spirits is the old standby, but there are now products that are a lot easier to apply.

Here is an edited version of an answer I just gave another reader: Some concrete or masonry sealants are not available in a number of states because of the solvent in them. So the industry is moving toward water-based sealants that have proved to be very effective and more environmentally acceptable. Euclid Chemical makes Baracade WB 244, a siloxane/silane-based blend that provides deep penetration and good surface repellency. There are others, such as Sika Clear Sealer, which Home Depot carries in its masonry section. Masonry-supply houses in your area may also carry other brands. The driveway will need to be thoroughly clean and dry before the sealer is sprayed on. You can clean it with TSP-PF, following directions on the container.

Q. You are my oracle in house care. I have been following your columns on cedar deck treatment with interest. Our untreated cedar deck is now 11 years old and weathered. I just scrubbed off accumulated mold and lichen with a stiff bristled brush and plastic scrub pad, using Simple Green and a little bleach. Now is the time to do something. I know you like Amteco TWP 100 series, which needs annual treatment; the guy at may hardware store said Bond’s One Time is the new hot skinny and lasts up to seven years.

A. I have no personal experience with this “new hot skinny” product your hardware store is trying to sell you, but do keep in mind that “up to seven years” means just that. It may fail much sooner, as have some of the other products some readers of this column have written me about in despair, after trying them on the recommendations of their favorite stores. Bond’s One Time is a clear coating — not a stain — and is quite expensive at $75 per gallon. Its one advantage seems to be that, according to the manufacturer, when the time comes to reapply it, it can be done, after proper preparation, without removing the previous application. But so can any of the Amteco clear or semitransparent stains.

If this product is that new, it has not stood the test of time, and it may or may not measure up. Consumer Reports is testing it now but hasn’t reached a conclusion because it has not gone through its one-year exposure test, which is an accelerated three-year test. One consumer has reviewed it and scored it as excellent, but he hasn’t even had it for two years on his new deck. He compares it to other products he has used in the past, but he does not say which they were.

Amteco’s product line was recommended to me many years ago by a former member of the Texas Forest Service whose job was to test coatings that would withstand the harsh Gulf Coast climate — a hot, damp and punishing environment. He told me that Amteco was, by far, the best-performing coating he had tested. Since that conversation with him, I have used it myself and recommended it to clients who have been very happy with the results.

I know other products have come on the market since then, but some of them haven’t proved to be as long-lasting as claimed.

Amteco TWP Series 100 semitransparent stains do not need annual recoating if applied correctly on a clean and dry surface. These stains can last five years, depending, as all coatings do, on the traffic, whereas a clear coating will need more frequent applications.

If you decide to try this “new hot skinny,” please let me know if you are happy with the results, which may take some time to determine.

Q. I have a chimney out of which the furnace no longer vents; it is used to vent a water heater. I realize I need a smaller diameter liner to compensate for this loss of hot air. My question is, do I need stainless steel or can I use an aluminum liner? I have been told differing opinions.

A. If the water heater is heated with gas, you need only a 3-inch aluminum vent, but if it is heated with fuel oil, you need a 3-inch stainless steel liner. You can use stainless steel for gas as well, but it is quite a bit more expensive.

Q. You mentioned in an article that there is a bathtub caulking that is mold/mildew-proof. Would you please provide the name and how to order?

A. The product I mentioned is DAP Kwik Seal Plus Premium Kitchen & Bath Adhesive Caulk with Microban. Because of its claim that it is mildew-proof, I tried it some time ago and commented that it seemed to work very well. It remained sparkling white and did not mildew. Unfortunately, it began to peel off the wall in about a year.

Q. In a century-old house with a stone foundation (pointed with concrete), concrete floor and about 5 feet in height, is it better to set up a system that continuously circulates exterior air through the entire basement or run a dehumidifier 24 hours a day all summer? The latter uses a lot of electricity and is therefore expensive. It would seem a “whole basement fan” would be a lot cheaper to run, and if ductwork were set up properly, would do a better job than a dehumidifier that can’t really move air in the distant reaches.

A. Assuming you live in a climate with hot and humid summer weather, introducing and circulating exterior air throughout the basement is likely to cause condensation on the old stone walls and the concrete floor. It can also cause what I assume is old floor framing to absorb some of the ambient air’s moisture, which may not be too healthy for it. If the old framing was replaced with a standard joist system, mold may form on it.

The thinking has changed with experience. Whereas crawl space ventilation was code-recommended decades ago, so much rotting first-floor framing was found that today’s recommendation is to close all windows and run a dehumidifier. If the basement windows and exterior door are not tight, the dehumidifier will run for longer periods; consider caulking and weatherstripping these openings.

The moisture content of air seeks its own level, so the air in the “distant reaches” will reach an equilibrium with the air close to the dehumidifier. If you set its humidistat at 50 percent, the dehumidifier should not run all the time once it has cleared up any excess moisture. You will either have to empty the pan daily or have a way to dispose of the condensate automatically into a sewer line or through a sump equipped with a pump.

Q. My wife and I live in a ranch-style home with a full basement. We’ve lived here 33 years and never had a problem with water in the basement until this year. We don’t have a sump pump. The water this year covered the entire floor with about an inch of water. A contractor we spoke with explained that due to the high water table, the drainage pipe around the base of the foundation couldn’t do its job properly, and the water found its way into the basement between the floor and the walls of the cellar.

We have it under control now, but there is a white, fluffy substance on the walls and the floor. I’m not sure what this is, so I’m asking if you have been made aware of this situation before and how was it handled. I spoke with a person in the restoration business who thought it might be a residue from the cement, but he wasn’t totally sure. Is this stuff safe to handle? What would you recommend as a cleaning agent?

A. The whitish powder at the base of your poured concrete walls and on the concrete floor is efflorescence. It is made of the salts found in all masonry, which have been dissolved by water and left on the surfaces as the water evaporates. This process is similar to salt flats, which give us sea salt. These salts are harmless and can simply be brushed off with a stiff brush. If this does not completely remove them, you can wet the brush. However, I would not recommend that you use them to season your food.

Ÿ Henri de Marne was a remodeling contractor in Washington, D.C., for many years, and is now a consultant. Write to him in care of the Daily Herald, P.O. Box 280, Arlington Heights, IL 60006, or via email at henridemarne@gmavt.net. His book, “About the House,” is available at www.upperaccess.com and in bookstores.

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