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Tips for replacing a cedar shake roof

Q: I am considering replacing my deteriorating cedar shake roof with a steel roof. My home is in the Chicago area and is a Cape Cod with a fairly steep pitch.

What considerations should be undertaken prior to a decision?

The current roof has spaced planking. Is it advisable to install an ice/water shield on a steel roof?

Can you advise the best ventilation for this roof with no soffits? — Illinois, via email

A: If you are selecting to install a screw-on metal roof — a less expensive metal roof than standing seam, but not as good overall — you may be able to apply it over the existing cedar shakes if the planes they form are regular. (The photos you sent do not show that clearly.) Cedar shakes vary so much in thickness that this may not be possible.

If you can keep them, they should be covered with 30-pound felt or another underlayment to provide protection against the condensation that usually occurs on the underside of metal roofs.

If the shakes are too irregular, one option is to strap the roof from rake to rake and screw the metal panels to the strapping. Another option is to remove the shakes.

It will be difficult to install this type of metal roofing with the complexity of your several roof planes; the flashing will present a number of problems.

A better choice is a standing seam roof.

The shakes should be removed (they can be used for kindling) and new plywood sheathing nailed onto the existing strapping.

The plywood will have to be covered with a water repellent material, as detailed above.

You should have an ice and water protective membrane installed in the valleys, at the eaves and around any roof penetrations as insurance against leakage, since you will also need to have snow guards installed. These will be necessary not only to safeguard your gutters, but also to keep snow from sliding off your several steep roof planes and, since you have no overhangs, from blocking the four exterior doors under the eaves.

With snow prevented from sliding off the roof, ice dams could possibly develop and cause leaks at the seams unless your chosen roofing contractor uses a double-lock system with a polyurethane sealant applied to the seams prior to the double-locking. The contractor should also cut the metal so that it is possible to seal the ends of all seams with a crimped tab after inserting sealant in the seam terminations.

Be very selective in the choice of a standing seam roofing contractor. You should insist on 24-gauge metal, double-lock seams and the application of a sealant at all seams.

Too many roofers will only use 26-gauge metal (a lighter metal that can “oil-can” in strong winds) and single-lock seams without sealant or termination tabs in order to keep the cost down and be more competitive.

The cost will be higher, but you’ll have the best roof you can have.

As to ventilation, I see several gable vents airing very small attic spaces above rooms with slanted ceilings. If these small spaces have no access, you are not able to see if all is well. So, unless you can see signs of moisture on those slanted ceilings or where the rafters connect with knee walls, I would just leave things as they are.

A VERY INTERESTING COMMENT FROM A READER: I received the following response from my recent answer to a Worcester, Massachusetts, reader who was having a leakage problem in the pipe connecting her mother’s toilet tank and bowl. I was curious as to why her plumbers did not suggest replacement with a new toilet, and wondered if I was missing something. Obviously, I was.

”Here is a helpful possibility: It may be against the plumbing code to repair ‘high-volume’ toilets, especially in a ‘gentrified’ area such as Worcester. It may be that the plumbers, et alia, know that unless the soil pipe is replaced with a much larger one for the low-flow replacement, they’ll be called back to ‘make it flush.’ The original purpose of the divided toilet was to force flushing.

”They may, given the client’s gasp at the estimate, just not want to deal with kludging some new copper pipe with bodged fittings, only to be called back when (not if) it leaks. I wouldn’t even bother with it, and I’ve been jury-rigging this 1920s house for 33 years. Two of the three toilets are now handicap-height, and the third is in my wife’s attic office, only used by a 5-foot-7 woman with a low center of gravity. Even that 50-year-old one has a 2-inch soil pipe.”

Q: I saw your response to a basement leakage situation and I really appreciate your advice. I am in the process of purchasing a 40-year-old house with a full, unfinished basement.

We noticed at inspection horizontal cracks on the block foundation wall 30 inches to 36 inches below grade. There is no visual deflection on the walls, though, and they are 90-degree upright.

The horizontal cracks are more than 10 feet long on one side — and just a crack line with no visual gap or opening — and about six feet on another side. The basement is dry now, but there are some old seepage marks on the floor.

I would like to finish the basement at some point, and I am worried that if this is a major issue it might turn out to be a deal breaker. I’d appreciate your input, please. — via email

A: The description of the cracks is the telltale of block walls having suffered from some frost pressure. Fortunately for you, this pressure seems to have been minimal since you cannot see any deflection in the walls.

Masonry is unforgiving, and it takes very little pressure for cracks to develop. The important thing is the width of the cracks and what deflection the walls are showing.

The seepage marks on the floor may have been caused by an earlier grading problem. Ask the sellers to give you the history if they know it. It is also possible that they are not the original owners and that the leakage occurred before their time.

I suggest that you check the grade all around the foundation. If the ground slopes away from the house and all appendages (patios, walks, driveways, porches, etc.) do not drive water toward it, you are probably OK.

Q: I read your columns regularly in the Pittsburgh Tribune-Review and have found your advice helpful in various situations that I have encountered. I wonder if you may have a solution to an annoying problem that I have.

We have a second-floor gas water heater that supplies the heat for our first floor through radiant heating. The water heater is located in a utility room along with a second-floor furnace. The water heater is vented through the roof via a 4-inch pipe that is capped with a “whirlybird” or turbine vent. The problem is the vent.

There are two issues:

One is that when it is very windy, the turbine seems to reverse motion and the exhaust from the heater is blown back into the pipe. Sometimes that blowback is so intense that it blows out the pilot light and it is necessary to reignite it. This is very annoying when it occurs at night and is not discovered until the next day. Not to mention concerns about the exhaust coming back into the house.


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