Solving the mystery of the yellow snow
Q. We live in South Burlington, Vt., in a free-standing (two to a unit) condo. After the last two snowstorms, we have noticed a yellow liquid dripping off the roof. Our roof is 9 years old, the age of the development. This phenomenon is only happening off the front of the house and not the back, and we have noticed only one other neighbor, the one across the street, to have had the same problem but not to the extent as ours. And not this last snowstorm. Just ours. The snow gets a yellow tinge and then ice forms underneath it that is very yellow and is dripping onto our driveway as it melts in the form of yellow water.
We are so perplexed as to why this is happening only on the front of the house and not the back. The only other thing we have noticed is that on one of the windows and on one column on our front porch is a soot-like substance, perhaps from a neighboring house with a wood stove. Would that have anything to do with it? We hope you can help us solve this problem, as we are becoming quite concerned about it.
A. The yellow snow and ice may be due to soot from a wood stove nearby. Had the yellow staining been only in the dripping off the roof, I would suspect it to be from the asphalt from the roof felt leaching out because water backed behind ice dams and got under the roof shingles. But if the snow itself turns yellow, that should not be the case. Sorry I can't be of more help.
Q. I read your article regarding the waterproofing of basement walls that are made of cinder or concrete blocks and clay tiles. The reader referenced an article of Dec. 11, I assume 2008. I have been unable to find a copy of that article. My papers have been recycled, and it is not available on the Star-Ledger archive site. Would you be kind enough to let me know where I can get a copy of that article?
A. Rather than have you look for it, here is a reprint of my earlier response to a reader who asked about waterproofing his or her cinder block foundation: Cinder block walls should NEVER be waterproofed from inside. It would trap water within their cores, and the water level, not having a way to drain, will rise. The only escape for the accumulated water is to evaporate in your living space. Humidity will increase to intolerable levels and mold will develop, endangering your health and making the dwelling uninhabitable; I have seen that happen in several cases.
The proper fix is to have the moisture problem taken care of from the outside. The grade around your house should be checked. All flat or negative grade (sloping toward the house) should be raised to divert water away from the foundation. Downspouts must discharge on concrete or plastic splash blocks that move water a few feet away from the foundation. No depressions should be left near the foundation; they should be filled.
All appendages such as patio, walk, driveway, etc., that slope toward the house need to be resloped. (If that is a problem, write again with specific details for a discussion.) This can be expensive, but it may be necessary.
If the foundation is so close to the ground now that it is not feasible to raise the grade, leaving the 8 inches of exposed foundation required by most building codes, you may need to use an alternative I have used many times. Let me know whether that applies to you, and I'll discuss it.
I hope this answers your concerns. If not, please provide more details.
Q. We recently read your column regarding the removal of spots on wood siding. You recommended sodium per carbonate to remove what seems to be mildew or mold. We have noticed in our area of Warren County that, on many homes where the roofs are facing north, there seems to be streaking from the rooftop down to the gutter in a gray-black discoloration. Most of these roofs are of a light color, and it is, therefore, quite noticeable.
Our house also faces north. It was built nine years ago. The roof is a 30-year GAF Timberline shingle in the color "Mission Brown" installed over No. 15 felt. We have noticed that where one gable of the roof meets the flat part of the roof, there is a definite darkening of the shingle. In addition, there is also one section of streaking noticeable. Our question is: Can we use sodium per carbonate to clean these areas without harming the color and the rest of the roof? We are also concerned to do this cleaning in an environmentally safe way.
A. I haven't had any experience with the use of sodium per carbonate for roof algae. However, this product is environmentally safe to use, so I don't see any reason why it can't be used, and it may very well work effectively.
Competitive commercial products sold for cleaning roofs are based on sodium hydroxide. You may want to be the guinea pig and try sodium per carbonate; be sure that you use one of the ultra-concentrated oxygen-bleaching products. I would appreciate your report on the results.
Here is a reprint of my answer to a similar question from another reader several months back, describing a treatment that has been used for many decades and really works. I've added some additional information.
The black streaks are caused by algae growing on the asphalt shingles. To remove them, spray the roof with a solution of three parts fresh Clorox bleach to one part water with a garden sprayer on a windless day. Work from a ladder, not by walking on the roof, as it can become slippery when wet. Wear goggles, old clothes and rubber gloves.
Spray only enough to wet the shingles, and avoid as much runoff as possible.
One gallon of the mixture covers 50 square feet of roof surface. Before you start, thoroughly soak any vegetation below the roof and cover it with plastic. If you have metal gutters and downspouts, keep running water in them while spraying and until all runoff stops, as the solution is very corrosive. When you are finished with the spraying, wash the plastic thoroughly with your garden hose and spray the plantings again. It will take several weeks before you see results. Not too environmentally safe, but very effective.
You can buy ready-made formulas to remove algae. Roof Deck Cleaner, a concentrated form based on sodium hydroxide, can be purchased through the Shingle Shield Web site at shingleshield.com. To prevent recurrence, install special copper or galvanized strips on each side of the roof directly below the ridge vent. An easy way to find and install these strips is to get Shingle Shield strips online. ZincShield is another choice (800-440-3010); they also sell LiquidZinc for treatment of existing growth.
Q. Please advise me on any method to control and or eliminate efflorescence on the brick surface of a chimney. Would cleaning the brick (scraping and acid wash) surface and then applying a waterproof coating followed by resurfacing with a veneer brick or cultured stone completely eliminate the efflorescence from reoccurring?
A. Efflorescence is caused by water that has dissolved the salts in the bricks and evaporated, leaving the salts on the surface - much like how sea salt is gathered when seawater is ponded and allowed to evaporate.
To prevent efflorescence, you need to keep the bricks dry. Bricks can absorb water in several ways: unsound mortar joints, a porous surface or, often, from the top of a chimney through a broken, missing or inadequate cap. Find and correct the source of the water in the bricks first, then simply remove the efflorescence off with a stiff brush. If that is not sufficient, wet the brush and scrub again.
Q. My driveway extending from the street to a two-car garage is on a slight slope and is about 40 feet long and about 10 feet wide.
There are three cracks about 1 inch to 2 inches wide running from side to side. The 2-inch crack is not even from side to side, and the other two are even. The rest of the driveway is in good condition.
Do I repair only the cracks and then resurface the entire driveway? Or do I tear up the whole driveway and repave it? What repair materials would you recommend for this job?
A. You didn't say whether your driveway is concrete or asphalt. I will assume that it is asphalt, as asphalt, being a liquid in solid state, can break and creep on an incline. The cracks being across may be an indication that this is the case.
Of concern is the 2-inch crack that has one side higher than the opposite side (if I understand you correctly). This often indicates that some settlement or erosion is taking place.
There are asphalt-repair products you can buy in bags and use to fill the cracks. This will allow you to keep an eye on what is happening before getting involved in an expensive replacement. If your driveway is concrete, write again with as many details as you can, and photos, if possible.