Mice can squeeze into house through tiny holes

Posted7/15/2012 5:29 AM

Q. I am having trouble with mice. I have looked everywhere but cannot figure out how they get in the house. I see some small openings around where the electric cable goes into the house at the basement level, but it seems too small to let them in. I'd appreciate any suggestions you have.

A. Mice can get through holes as small as a quarter-inch. Their fur makes them look larger than they are.


The small space you have identified is a likely point of entry. There are probably others around the foundation, such as an outside garden hose bibb, the holes where a gas pipe or oil filler and breather pipes enter the house, etc. Small spaces where the foundation meets the first-floor framing are also possible entries; these can often be caulked.

A great product is available for sealing small spaces that are nonetheless too large to be caulked: the Xcluder Rodent & Pest Barrier. It comes in a kit that includes a stainless steel/poly-fiber mesh mat, several strips of the same material, a pair of blunt-nosed scissors for cutting and pushing the Xcluder into small spaces, and a pair of neoprene gloves to be worn when cutting the mesh to the right size to avoid getting slivers of steel in your skin.

The Xcluder is made in the United States, an important point in this age of outsourcing, and can be purchased online at www.buyxcluder.com for less than $10. The kit also has instructions for effective installation and some interesting facts about rodents, which carry diseases and can cause deadly fires by chewing on electrical wires. This information should convince those who find mice cute that they are dangerous pests.

Q. I emailed you a few weeks ago thinking I had silverfish. After looking up silverfish and firebrats on the Internet, I realized that is not what I have. These insects are brown on top and have a grayish underbody. They seem to like moist places and come out at night. The adult size is about one-half inch long. Do you have any idea what these are and how I might get rid of them?

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A. Sorry, but I can't identify these critters with so little information and without a photo. I suggest you catch one, put it in a small plastic bag and take it to a local pest control operator or the entomology department of your local extension service.

Q. I read your column in the Daily Herald and enjoy all the useful information it provides. I live in a house in northern Illinois. The property is surrounded by wetlands and ferns. A constant influx of water comes through our drain tiles and into the sump pump due to a high water table or spring nearby. Our sump pump has done an excellent job of keeping our basement dry.

My question is, what is the proper level to set the sump pump to turn on? My sump pump begins pumping after 6 inches of water has entered the pit, resulting in frequent on/off cycles. My neighbor has his sump set up so the water in the sump pit levels off at a certain point and the drain tile leading into the pit ends up being half submerged, resulting in much less frequent on/off cycles. I am assuming it levels off at this point because that is the height of the water table.

Which setup is correct and why? I have a Zoeller submersible primary pump with an Aquanot AC/DC backup.

A. There is no set rule. Your submersible Zoeller pump has a float that triggers the pump, and it is possible to adjust it on certain models. You can call Zoeller's technical service at (800) 928-7867 and follow the prompts, or email the company at webmaster@zoeller.com to find out if the float on your model can be adjusted. If it can't, and if you want it to come on less frequently, you can set it up on a couple of bricks.


Q. We installed a wooden atrium door 20 years ago at the entrance to the breezeway that connects the house and garage. In the past year, I have noticed deterioration on the bottom of the fixed portion of the door. I am wondering if it is possible (feasible) to remove the window and replace the deteriorating board with pressure-treated lumber. I have enclosed photos.

A. Thank you for the photos. The outside shot shows the damage to the bottom rail of the fixed panel door, which is due to rain hitting the door or splash from roof water bouncing off the ground onto the door and getting into the wood because of a poor seal between the glass and the bottom rail.

The inside shot appears to show a square molding that is retaining the glass panel. You could ask a skilled carpenter if this molding can be removed without breaking it (if it does break, a new one can be fashioned), which would allow the glass to be removed.

Pressure-treated lumber is not the wood to use in replacing the bottom rail. Millwork is usually white pine that has been treated with a wood preservative. Pressure-treated wood is yellow pine that has different characteristics and would not be compatible.

It may be possible to replace the bottom rail with one of the new composite materials available, but it may be less expensive to replace the fixed panel entirely. To prevent a repeat of the damage, the seal between the glass and the wood will need to be carefully maintained; it should be painted every couple of years.

Q. Three estimates have been requested and obtained for vinyl siding for my 35-year-old house. They are all within the same price range and job description. The only question is your recommendation. If you have had experience with these, which would be your choice and why: Norandex Woodsman Select double 4-inch vinyl, Mastic Carvedwood 44, or CertainTeed Monogram 46. Visually and the installation lengths of the Monogram 46 were the only consideration for my choice at this time.

A. All three brands are well-established. It's really a question of which one you prefer and the reputation of the installer.

You may want to ask for references from three or more jobs each firm has done in the last two years. Call the customers to find out if promises were kept, if the workers were clean and courteous, and if the job site was left clean at the end of every working day. Also ask if there was a sudden discovery of something "unanticipated" that required a large additional sum -- often a trick to bid low and, once you are trapped, hit you for more money. Was there any reason to call the workers back and, if so, was the response prompt and the work performed satisfactorily?

The answers to these questions are far more important in selecting a brand than whatever difference there is between the actual products.

Q. Thank you for your thoughtful response to my question on how effective zinc strips are in getting rid of moss on my roof. You suggest patience, and I really don't want to get into power washing. Think I'll spray the moss with a 50/50 Clorox solution to speed the killing process. Any comments?

A. Please be advised that using a Clorox bleach/water mixture will not hasten the cleaning of your roof. It will still take a lot of time. There is also a debate about how effective this mixture is on moss and lichens. This formula is recommended for algae.

The formula found effective for moss and lichens is three parts white vinegar to one part water, and it will also take a long time to see results.

Q. I am going to be flooring my attic soon and, while thinking through the optimal time to do this without losing 50 pounds in perspiration in the process, have been wondering why folks never insulate their roofs.

I am acquainted with some of the reasons for keeping the roof cool (it increases shingle life, reduces heating bills from lost heat through the roof, etc.). These are excellent arguments in favor of good attic floor insulation, but I have never heard of anyone insulating their roof. It strikes me that placing insulation between the trusses should, in theory, prevent at least some of the heat during the summer, and the cold during the winter, from entering (or escaping, as the case may be) the attic space. Nevertheless, I have never seen or heard of any homeowner doing this and was wondering why. Any insights would be appreciated.

A. There are times when spraying closed-cell polyurethane insulation between the rafters makes sense. For instance, it does in cathedral ceilings, as fibrous insulation often results in moisture problems and decay. It also makes sense if the attic will be finished into living space.

In these cases, no ventilation is provided, and some building scientists have argued that ventilation is not needed. In general, shingle manufacturers disagree, and I know that when I handled warranty claims against failed shingles for clients, I was always asked to prove that there had been effective ventilation before the manufacturer would even continue the discussion.

The main reason it is best to insulate between an attic's floor joists as heavily as recommended for any given climate is that insulation should be surrounding the conditioned space. It makes no economic sense to insulate an attic that is kept empty or used for storage. The better way to temper the elements is to provide effective ventilation by means of continuous soffit and ridge venting. This will keep the attic cooler in the summer and dissipate any moisture in the winter, as long as we are dealing only with outside-generated moisture.

Heated-space moisture must not be allowed to enter the attic through convective spaces.

Q. I've been monitoring the temperature and humidity in the attic since I installed a metal roof to replace my asphalt shingles. I became curious as to the efficiency of my soffit and ridge venting.

I wrote to a site that answers questions about metal roofing. Now I am getting a variety of opinions regarding negative pressure in the attic. Some say the ridge vent should not exhaust too much air, as this will lead to negative pressure and draw moisture and conditioned air from the living area. Others say it should be 40 percent soffit, 60 percent ridge. It seems there are as many opinions as contributors.

A. Here is one more opinion. Now you will have to decide which one to believe.

I disagree with both opinions stated above. The net free ventilation area (NFVA) of soffit vents should equal or exceed the NFVA of the ridge vent. Under these conditions, there can't be negative pressure in the attic that will rob conditioned air. Even if the ratio is reversed, as in the second opinion, there is not enough "suction" from the ridge to affect the conditioned air unless there are significant convective paths. They should be sealed in any case.

What robs conditioned air is the use of an attic fan in summer to reduce the temperature of the attic and in the winter to remove excessive moisture that should not be allowed in the attic through convective paths in the first place. This occurs as there is seldom enough NFVA intake to satisfy the CFM requirement of the fan.

• 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.

2012, United Feature Syndicate Inc.

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