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posted: 11/24/2013 12:32 AM

Multiple ridge vents could lead to problems, not solutions

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Q. I read with great interest your article in which you recommended continuous baffled ridge vents.

I am in the process of replacing my 10-year-old roof due to a manufacturing failure, so anything I can do to prevent future failure will be a good thing.

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In my research on these ridge vents, I came across an article written by a vice president at Air Vent Inc., who stated that if there are other parallel or perpendicular ridges that are more than 3 feet in distance from the main ridge, they should be separated by plywood or plastic sheeting in the attic or should not have a vent. The reasoning is that, under certain wind conditions, the higher ridge could draw air from the lower ridge instead of the soffit vents.

I have two perpendicular ridges, (one in front, one in back), about 8 feet long and about 3 to 4 feet below the main ridge. I really don't want to climb in the attic and separate the two areas because this is a fully trussed roof and it's very difficult to move around.

What is your take on this? Should there be no ridge vent on lower ridges? Use conventional vents on the lower ridges, and continuous baffled vents only on the upper ridge?

A. By distance, you mean more than 3 feet lower than the main ridge. Under the scenario you describe, it is probably best not to install ridge vents on the lower ridges. If these two lower attics are open to the main one, they are likely to be protected from excessive moisture since moisture seeks its own level. If this is the case, higher relative humidity (RH) in the two lower attics will be drawn to the lower RH in the main attic, and the ventilation would prevent any moisture buildup that would cause mold or mildew.

The most important consideration is to make sure that all convective paths from the living spaces to the attics are eliminated, as no passive ventilation system can overcome this situation. This is best done with a blower-door test.

Q. We have discovered a fluffy mold-type growth on the basement walls of our 1930s house's cinder block foundation. It comes out about an inch from the wall at its "tallest" and is light gray. It starts about 4 feet below grade and goes down to where the wall meets the floor. It's not a complete coverage, but it is present on all four walls.

We've lived here for 30 years and haven't noticed it before. There have been no changes to the grade around the house, nor removal of trees or any major alterations outside. We did have a new high-efficiency furnace put in two years ago and the basement is much, much colder than it used to be. Any ideas of what this is and what we should do about it? I've attached some photos.

A. The growth is efflorescence; it is not a mold, but the salts from the cinder block units (salts found in all manufactured masonry products) left on the blocks' surfaces after the water that dissolved them has evaporated.

Strange as it may seem, this efflorescence may have been encouraged by the replacement of your old furnace, which required makeup air to satisfy its combustion needs and obtained it by drawing outside air through the many cracks and crevices found in old houses.

Modern, efficient furnaces get their makeup air from outside and run much cooler than old furnaces, hence your cold basement, which is no longer heated by the radiation and static losses of your old furnace.

The efflorescence can be removed easily with a dry brush, but the fact that it occurs tells me that you are having some moisture transmission from outside through the block foundation. The heat losses of the old furnace caused this moisture to evaporate much faster, since warm air holds a lot more moisture than cold air can, and the air exchanges the furnace created helped dissipate the moisture.

Q. Don't laugh, but my walls (inside) haven't been painted in 40 years. They were last painted in the early 1970s with latex. The paint stores all say the walls need to be cleaned with TSP first.

I have two concerns: First, I'm worried about not rinsing them well enough; and second, I have pretty bad shoulders, which will make scrubbing walls very painful. I can get away with using a roller, but I wonder if there is some product or some type of paint that will let me eliminate the scrubbing. If not, then I'll just have to tough it out.

A. You can clean the walls with ammonia by following the instructions on the bottle, which gives you the proportions to mix with water, vinegar and baking soda. Once cleaned, wiping the surfaces with a damp sponge should be enough.

It may also be wise to apply a primer before the finish coat.

Q. I own a 53-year-old ranch in western Pennsylvania. The full basement is below ground with a door and three block windows. Shortly after the house was built, my late husband's grandfather painted the block walls.

We have dampness and, in one corner, mold. This corner has two very large shagbark hickories about 10 feet from the house. Of course, this causes shade. Some of the other areas in the basement have covered walls, ceilings and floor, so who knows what is going on behind all of it.

My son wants to waterproof the block walls. I read your column and know you have covered this subject, but I can't remember the details. I know once the walls are painted they are difficult to waterproof.

We do know that the ground around the house should be sloped away from the house.

Can you offer any suggestions as to what we should do and your opinion on the trees shading this area?

A. By all means, keep the beautiful hickory trees; they are very unlikely to have caused the moisture problem. Grading and control of roof water are more likely the culprits. That's what needs to be addressed.

To diminish the risk of water penetration through the blocks, you should correct any grade deficiencies that allow water to run toward the foundation or pool next to it. Also make sure that roof water is controlled with gutters and downspouts that discharge water on a splash block sloping away from the foundation.

If you do not have gutters, set concrete patio blocks flush with the sloping grade at the drip line of the roof to prevent the formation of a depression, which allows water to penetrate deeply into the soil. Plant grass or a thick ground cover; avoid flower beds and mulched areas.

Cinder block or concrete block foundations should never be waterproofed from inside because any moisture penetrating the blocks from outside will be trapped within the blocks' cores. The water can build up to a very high level as its only way out is through evaporation into the living spaces -- with disastrous results.

Q. I enjoy your column in our local newspaper, The Daily Herald, and have a great respect for your opinions.

We have some concrete walkways and a concrete pad (3-by-4 feet) at our service door to the garage, all of which have sunken. We are considering concrete leveling, but are concerned about pumping a slurry into the ground. We have received an estimate from A-1 Concrete Leveling and Foundation repair, a franchise company. Your advice is requested. I know we need to ask for references. Should we be wary of guarantees by a company that has not been in business very long? Is there a better solution to our problem, short of replacement?

A. It is always safer, when in doubt, to deal with a firm that has a long history of quality, performance, good service and integrity, but newcomers also need to be given a chance. Even the best that have been around a long time once started small and new. Franchises may also be helpful in training and backup in case of questions or problems.

Pumping a slurry in the ground is not really a problem.

Yes, do ask for references and call the former customers to see if their jobs are holding up well and if the firm acted responsibly.

Q. I owned a house that had aluminum shingles that looked somewhat like regular asphalt shingles at first glance. It was built about 1935 and the roof is still in perfect condition. Is this type of shingle available? It seems that it would be as easy to install as asphalt shingles, although the material cost would probably be greater.

A. Aluminum shingles are still available, as are other metal roofing shingles such as zinc and copper.

A great new tool: I have just tried the new Black & Decker MAX 8-volt impact driver and it is quite impressive. It is ideal for the average handyperson. Most other impact drivers cost anywhere from $100 to $200 plus, and are more geared toward contractors. They may be considered too pricey for homeowners.

This driver feels solid and delivers very high torque. Its chuck is unique in that you pull it out to insert the bit and out again to remove it. It has an LED light to illuminate the work area. It's also very compact, which makes it easy to work in tight places.

I haven't used it long enough to see how long the battery will last before needing to be recharged, but that should not be a problem for DIYers. At a cost of just under $40, it's a tool that belongs in every shop. It will be available in November on Amazon, at certain retailers, and directly from Black & Decker. It will definitely be on my upcoming annual list of holiday gifts.

• 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.

2013, United Feature Syndicate Inc.

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