Q: Our house roof drains on our garage roof. Is this common and is it ok to do this?

A: I see this all the time. Builders are still doing this on new builds but I don’t recommend it. I can show you multiple examples of a roof that is otherwise in good condition but has a section under a downspout that has been ruined by the added water of an upper roof hitting it. In a heavy rain you can see the water pounding onto the lower roof. It is not surprising that this added water will shorten the life of the shingles. I often walk all over a roof and find an area that has only a couple years of life left while the rest of the roof would likely be fine for at least another ten years. To me it’s clear that draining an upper roof onto a lower roof is a bad idea.

Q: We are deciding upon which shingles we should buy for our roof. Do you have any suggestions?

A: From experience I would say you need to have shingles that are wind resistant in this part of the prairies. Just a few weeks ago we had winds in excess of 100 km per hour. An un-tarred 3-tab shingle will often blow off in such high winds. Architectural shingles seem to be better designed and seem to hold up better to the wind. Shingle manufacturers rate their product for normal use and I believe under normal circumstances they do live up to that rating. The problem is in the installation in my opinion. Installers and homeowners sometimes rush and miss a nail or two and that is all that is needed to create a problem. I have always tarred every tab when installing shingles. This process takes time and would not be possible in the winter. If possible I recommend adding tar to hold the shingles better as this alone will increase the longevity of the shingles. 


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It is that time of year we all wait for, an end to winter. With the cold weather disappearance it is also a time for other problems to show up, In the case of today’s topic – Leaking ceilings.

You will notice I didn’t say leaking roofs as a leak in a ceiling could be more than just a leaking roof.  There are three primary reasons you may see water dripping from your ceiling in the spring or in the warm spells in the winter.

  1. Ice damming is the primary cause of roof leaks in the winter when ice is formed on the roof and eventually leaks into the ceiling of the home. Major factors in ice damming include ;
    1. Cold weather
    2. Snow loads on the roof
    3. Lack of insulation and or vapor barrier.
    4. Inadequate ventilation of the attic.
    5. Attic frost is the second most common cause of leaking ceilings in the Midwest. Factors that contribute to frost in the attic include;
      1. improperly vented bathroom vents
      2. large openings in the ceiling structure which allow warm air into the attic
      3. blocked or improperly insulated vent lines
      4. lack of insulation
      5. lack of ventilation
      6. 3.       Blown snow in the attic is the least likely cause of leaks but I do see it from time to time. The most common issues that cause snow to enter the attic is;
        1. Swirling snow on the roof which enters the roof vents
        2. Wind driven snow which gets into the fins of the turbines of the whirly birds
        3. Snow coming in through the gable and ridge vents.

Ok now that we know what the causes are of the leaks we need to discuss why the ceilings eventually leak. Most people have the misconception that insulation stops heat loss so the more insulation the better.  This is not quite right. First of all insulation is meant to slow the rate of heat loss, not eliminate it. This means if we add heat to a room for 15 minutes for example it will make that room comfortable for an hour let’s say.  The heat loss is primarily up through the ceilings as heat rises. In this case the type of heat loss is through conduction. If someone opens a door then the heat loss would be through convection. Radiation is the last type of heat transfer that plays more of a roll in the problems we see above the ceiling. Radiation is primarily from the sun.

Here is generally how the insulation and ventilation all works or doesn’t work together to keep your home healthy and dry. Older homes primarily will have issues with ice damming while newer homes will have more issues with frost forming in the attic. Older homes did not value air tightness and attic ventilation as much as we do today. For instance older homes did not use vapor barrier and many of the homes did not have any soffit vents. Some older homes did not have any eaves at all so adding soffit vents is impossible in that case. The heat in a room in the winter months is usually around 20 degrees while the outside temperature is – 20 or colder. This means the heat in the room is moving up through the insulation until it reaches the cold attic space. In a properly insulated and ventilated attic the warm air mixes with the cold (-20) attic air and eventually is pushed or pulled out of the attic harmlessly. The problem is that sometimes the warm air is not mixing with enough cold attic air above the insulation before it touches the sheathing on the roof. Now the heat energy in the warm air is being transferred to the roof sheathing (wood) where it in turn moves up into the snow above the roof.

Ice damming is now beginning to form on top of the shingles. As the warm air melts the snow on the roof it starts to run down toward the eave where it meets the outside wall.  At this point the water freezes because there is no longer a source of heat feeding the melting process. Each time there is excessive heat loss up through the insulation and the weather conditions are just right you will get more melting. If there is a large buildup of snow on the roof it will act to insulate the heat in and encourage more melting. Now the ice at the eaves gets thicker until it is 4 – 10” thick and large ice cycles will also hang off the eaves. This big chunk of ice at the eave is now acting like a water dam for more melt water that is running down the roof. When the dam is high enough the water behind the dam is high enough to run up under the shingles above it. Next thing you know you have water running in through your dam

Now that you understand ice damming you should know that there are several ways to prevent ice damming. I will assume you have done all you can with the insulation, vapor barrier and ventilation at this point. Once the home is experiencing ice damming it is a bit late to think about adding ice and water shield under the shingles and vapor barrier under the drywall. The suggestions below are ways to deal with ice damming from the outside.

  1.  The easiest thing you can do is pull the snow off the roof near the eaves so it loses its R-value and reduces the rate of melting on the roof.  Be careful doing this.
  2. Another approach is to try to melt the ice that has already formed at the eaves. The critical part is to provide a path for the water to follow off the edge of the roof. One approach is to use heat tape that can melt the ice. Another way is to use calcium or salt to melt it. I have seen some people use a nylon stocking full if road salt to melt a path through the dam but I don’t know how well that would work.

Newer homes with leaking ceilings are generally a result of poor ventilation and not because of vapor barrier or insulation although both those things can contribute to the problem of frost. The problem of frost is very similar to ice damming in that heat enters the attic from the warm conditioned space inside the home. The heat rises up until it reaches the sheathing and forms frost.  Improperly vented bath fans are a usual problem here as the warm moist air from a shower will add a lot of frost in the attic. Another possible cause of frost on the attic sheathing is extreme fluctuations in outside temperatures. This is something that is impossible to control and usually will not cause any problems inside the home. Visit this site as well for a great article on Ice damming.

I noticed my bathroom vent is venting into the attic space. I was told this is not good can you explain?

Adding warm moist air into a cold attic is not a good idea as the change in temperature causes the air to condense when it reaches its dew point. This condensation can accumulate on surfaces and cause rot or enough moisture to form running water that will run onto the ceiling or down the walls. Of course once the ceiling or wall materials are damp you may face a mold problem. It is best to vent all fans out through the gable ends or through the roof. Be sure to use insulated vent lines. These photos show what can happen to the sheathing if warm moist air hits the sheathing. This roof was very spongy and almost at the point that would require re-roofing the area.i13 i15

Whats wrong with my eaves troughs?


The downspout in this picture is plugged and has been for some time. As a result the eaves trough has been overflowing for some time and has rotted out the soffit. Chances are the outside corner of this home is also moisture ladden. These kinds of issues can lead to much larger issues if left unattended.

How do trees affect my roof?

Tree branches rubbing on shingles here are a bad combination. Here is a photo of the results of a few years of the action of the wind in the willows so as to speak. You can see the difference between where the shingles have been worn by branches and where the branches didn’t touch. Allowing this to happen will shorten the life expectancy of the shingles by seveal years.

Why is my roof sagging?

This photo shows a transition point where two rooflines come together. The resulting valleys that are created here have to be constructed to withstand the extra snow load in these areas. In this case the valleys have sagged considerably and an abnormally heavy snowfall may actually cause the timbers to crack and fail. This type of failure may not be observable right away until the snow melts and rains into the attic and through the ceilings. Many older homes were constructed this way and I have seen other similar issues such as sway backs in the ridge line (similar to the saddledome). Often times this movement happened soon after the home was built and likely hasn’t gotten any worse. Having said that I always recommend having a qualified contractor or engineer access the situation to be sure it is still structurally sound.
P.S. Any inspector worth their salt should try their best to gain access to the attic space as it is so important to the whole picture. I don’t often walk in attics for many reasons but there are times when I do in order to get a closer look at a potential problem.

Why do I have Moss on my roof?

Here is a common issue most home buyer will not be aware of until they see the damage coming trough the drywall below. The real issue here is that the wall cladding is too close to the shingles and is absorbing the miosture from the roof. The best practice is to either step flash or fully flash the wall and roof and leave about 1-2″ of space between the shingles and the wall. There is potential here for the moss which is moisture to rot the wall out and even cause structural failure. Notice also the evestrough is full. A dirty evestrough can also be a problem area for rot as water rots away the facia and ends of the rafter tails.


My shingles are not that old but they are curling. What causes shingles to cup and curl?

I have seen shingles that curl due to a manufacturers defect but most often the problem is due to an overheated attic space. I have been in attics that are over 100 degrees Fahrenheit. When the attic is poorly ventilated it creates an air trap and acts more like an oven then an attic. As a result the shingles may cup and curl. You might also find shingles that have alligatoring or severe cracks. From my experience I believe the three tabbed shingles are more likely to deform due to the heat described above. Best advice is to add vents in the soffits gables and roof to promote air entry and exit. 

My home has asphalt shingles. I’ve been told I should check the shingles for potential leaks, how should I do that?

First of all anytime you plan to get off the ground be prepared and don’t work alone if possible. On a low slope roof I generally climb on the roof if possible. Getting a top view of the shingles and roof penetrations is best but if you are afraid of heights you should stay on the ground.  Here is how I would do it.  Start on the ridge and work toward the eaves looking for missing shingles. I also look for open or improper flashings which are likely to leak. Cupped or curled shingles are a sign of problems as well. There may be loose rocks on the roof near the eaves as a result of ice damming which  makes the roof very slippery so be careful. If the eaves troughs contain a lot of rock from the shingles you know that the shingles are failing. Overall the entire roof should look the same. For the inexperienced I suggest looking for areas that are different. Usually a roof will fail in certain areas such as the south side first. If something doesn’t