Prevailing winds? That's what caused one side of our roof to "age" faster.

Sunlight hits the southern side more. Sounds like that plus improper attic venting for the space are combining to degrade the southern side.

Shall I have only one side of the roof replaced?

How to correct attic venting?

16 year old roof is more than likely nearing the end of its life expectancy anyway. If you are going to go thru with replacing it I would do it once. Just my .02.

Attic venting is done by several methods, depending on the design of the roof. The simplest design to vent is a gable end design with soffits. A ridge vent is created at the peak and soffit vents cut into the soffits. This design uses the natural hot air rises as the venting mechanism.

Hot air (in the attic space) rises to the highest part of the attic(under the peak). The ridge vent allows that hot air to escape . This tends to form a slight vacuum in the space, which draws cooler air into the attic through the soffit vents. This movement occurs without interruption, in cold or hot weather, unless something plugs one of the two vent areas.

Other venting can be done with passive vents(turbines/box) and with powered vents.

Googling roof designs and types of roof vents will bring up all kinds of articles on the subject.

Below is a picture of the bad side of the roof (the shingles are getting worse further below) showing the roof vents, and a picture of the soffit. How can I improve on attic venting in the most cost-effective way?

roof · More Info

roof · More Info

I think the sun exposure would be the main cause of the singles deteriorating more on one side than the other. Hotter attics also speed up the degradation slightly.

I would have all of the shingles replaced and have architectural shingles installed instead of the current 3-tab shingles as they are much more durable.

When you have your shingles replaced by a reputable contractor, have them also review the venting to ensure it is sufficient and balanced between the bottom and top of the attic space.

Proper venting will help your attic be a bit cooler in the summer and help ensure you don't get moisture build-up in your attic. You need to avoid too much ventilation at the top of the attic as it will create a vacuum effect along the ceiling and may create moisture problems in the winter than it solves.

There are not nearly enough vents on that roof. More like at least 6 minimum. A ridge vent would be much more efficient. As long as the vent spaces(under those soffit covers) provide enough soffit venting area.

The ridge vent can be installed when new shingles are installed, but the soffit covers need to be removed to assess the venting area.

Once the proper soffit vent spaces are in place(and recovered with those covers) and the ridge vent in installed, hot air rising will cool the attic space and create a much better situation for the roof shingles(and the rooms below).

The number of vents is dependant on the ceiling area below your attic.

What is that area (sq. Ft.) for this roof?

I would counsel against just putting a bunch of vents on top of your roof without someone doing proper calculations.

The ceiling area under the two sides of the roof (of the addition on the back of the main house) is about 840 sq ft. About a quarter of that ceiling area is a cathedral ceiling of a room, the rest of the ceiling area has a normal, flat ceiling.

Looking at my neighbors' roof vents, mine look like most of them in terms of size and number of vents in relation to roof size. A few of them have what looks like round, wind-driven turbines. Would that be an improvement?

Thanks, that's useful info! There are only those 2 rooftop vents for the entire roof, but I understand that venting may not be the issue, my neighbors have similar venting, and it apparently passed the building inspection when the addition to the back of the house was built.

A couple of questions: why are the shingles getting worse towards the bottom end of the roof? The sun exposure is the same for the entire roof side.

Also, how are these decades long warranties for shingles honoured? Is it a practical proposition at all? In other words, why shall I pay more for a 30 year warranty compared to a 20 year warranty?

I'm having a really difficult time understanding how the sun can be the culprit in Canada, when it is poor venting that causes that problem here in the US. The lower increased damage is because the air flow there is less and the heat build up higher. Very often, code requirements are not the optimum procedure. They are, after all, minimum requirements.

And in most cases an inspector is not going to calculate or even ask to see the calculations for the roof vents.

How to improve the venting at the low end of the roof?

Fully Vented Soffit and Ridge Vent.

By improving the overall attic space venting. Adding vents(ridge vent is optimum) and more vent spaces in the soffits. The more space for air to flow through, the faster the air transfer in the space, the less heat build up.

It can be more easily understood by using water flow. Except the direction of flow is reversed(gravity causes water flow while physics(hot air rises) causes air flow).

Visualize a tub full of water. To drain, you open the drain. Gravity is pulling down on the water. Water can only flow as much as the drain allows. However, the more drains there is, the faster the tub empties because there is more area for the water to drain into.

Reverse that image. The space in the attic is the tub. The vent(s) on the roof are the drains. The soffit vents control the amount of gravity. Twenty soffit vents will allow a lot of gravity, but only two roof vents(drains) will restrict the flow of air. Adding more roof venting area will increase the air flow. Which decreases the temperature of the attic space.

Weighing the arguments tossed up in this thread and based on what I see on my and my neighbors' roofs, I would not make big changes to the roof right away.

I would consider making sure that the soffit is fully vented, because the roof shingles at the bottom end of the one side of the roof are in bad shape, but in decent shape at its top end, considering the roof is 16 years old. As I mentioned in the original post, the shingles on the other side of the roof are in perfect condition from top to bottom, in spite of being of the same age.

What is involved in making sure that the soffit is fully vented? Just making sure that nothing is plugging the airflow at the soffit? How do I check that? Or are there other things involved? I am asking this, because some roof shingles along the bottom edge are in worse condition than others, so there may be something plugging the airflow at those worse locations.

install ridge venting when you replace the roof. lose the passive

vents and close up the holes prior to new roof install.

best of luck

Ridge venting is a good option. Just make sure your venting is balanced.

To see if the soffits are clear, poke your head up in the attic and see if you can see sunlight coming from the roof edges where the soffit is. That will tell you that they are clear. What happens most often is insulation in the attic blocks airflow from the soffits.

I do recall from you earlier comments though that you have at least a partial cathedral ceiling so you may not have attic access or be able to view all of the soffit from inside the attic.

Fortunately, the part with the cathedral ceiling is on the good side of the roof where I do not have to look. The bad side of the roof gets afternoon sun, so I will be poking my head up in the attic tomorrow afternoon and I am hoping for a clear view on the entire length of the soffit. Will report back.

Well, I poked my head up in the attic, but I could not see the soffit, the construction containing the insulation is obstructing the view. I would have to climb into the attic and walk over to the soffit to see it, but I would rather not do it. As far as I can see, the general condition of the attic is quite good if not perfect.

My wife thinks that snow load contributes to the bad shingles issue. She noticed that the snow on that side of the roof (of the addition to the back of the main house) tends to accumulate at the low and far end from the main house. That's where the bad shingles are. They get covered the longest and the thickest in winter.

Can snow load contribute to aging of the shingles?

On sun exposure contributing to the aging of the shingles: I myself notice that the roof shingles at the near end of the main house benefit from the main house shading them from the morning sun, these near end shingles are in better shape than those at the far end from the main house that get more sun hours during the day. That would be consistent with sun exposure contributing to the aging of the shingles.

I wonder if your roof has problems with ice dams and maybe the previous owner had damaged the shingles by aggressively removing snow and ice.

No ice dams this past winter. The bad shingles don't have streaks or similar as would be consistent with aggressive raking or some other method of mechanical removal. I checked with some local websites, and yes, snow load can apparently contribute to shingles going bad in this area.

My present thinking is that there is nothing wrong with my attic venting or roof design/structure. The cause of shingles going bad is probably increased environmental exposure by sun and wind leading to snow load, with all of the increased exposure (by sun/wind/snow) coming from the West to North-Western direction, that's where the bad shingles mostly are on the one side of the roof. As I alluded to, all shingles on the other side of the roof are in perfect condition, being in the shadow of the increased exposure with everything else being equal.

Any further comments as to replacing the roof? Previous comments include replacing both (good and bad) sides of the roof which I agree to, the roof is 16 years old after all. I am not sure if I want to pay for architectural shingles with a 30 year warranty instead of the usual 3-tab shingles with a 20-year warranty. I am not even sure about those decades long warranties being a practical proposition at all, the questions I tossed up in a previous post remained unanswered. Anyway, I welcome further comments!

I have not heard of anyone cashing in on a shingle warranty and I have also not seen any roofs where the shingles on the entire roof lasted past the warranty. I understand also that a lot of the warranties are pro-rated which means you would only get a portion of the cost of the shingles back if they fail.

I look at warranties this way: longer warranty = more durable shingle that will last longer.

With architectural vs 3-tab the architectural shingles are much more durable. If you have high winds there is a chance of tabs being torn off the 3-tab shingles.

Also, architectural shingles are only about 5% more expensive than 3-tab (shingles only-not installed). I don't know how the labour costs compare for installation though. I have installed both on my own houses and the labour seems about the same to me.

Another possible cause of shingles rotting is if a tree had been close & dropping leaves or needles that sat there & then rain or snow added to the decay, has a tree been removed or cut back that may have caused damage. I would go with 30 yr as cost & labor involved you don't want to repeat in 15 yrs. What is under the shingles? Plywood or some sort of solid sheeting or just attic framework. Out here you can put on 2 roofs before you have to pull it off down to sheeting or if none, put it on, that's a pretty big expense. If you would just be putting on the 2nd roof over the 1 on there then the30 yr would postpone the need for sheeting if it doesn't have it for at least 20-25 yrs. You put on 20 yr & need sheeting in 15 yrs big expense.

Is there a downside of installing better (more powerful) vents?

The airflow will be limited to what the soffits will allow and the better vents will cost a few dollars more, but are there any technical or other disadvantages?

just stay away from pav's (powered attic vents).

these vents pull conditioned air from house into attic,

and if ducts are also in attic, will pull conditioned air

from ducts at duct leakage sites.

not to start the old pav discussion that has been done

to death on this site.

best of luck

Also in Ontario here. I'm not a roofer, nor a roof expert, but my husband has done some repairs here and there on our roof, and we've both inspected it over the years. Your picture above is a bit dark to see. But are you are saying that the part of the roof which is darker is the part just underneath the eavestrough on the upper roof on the 2nd floor ?

If so, one thing to do is to make sure you keep the gutter clean and unclogged above that spot - because if there is constant water overflowing from the 2nd floor onto the garage roof right at that particular spot, you will find a lot of deterioration on the shingles where the majority of the water hits. We have small sections of our roof which deteriorates much faster than other areas specifically because water pours from the high roof to the lower roof. Watch during a heavy rainstorm to see if the water is properly going
down the downspout from the 2nd floor roof to the roof over the garage,
or if it is pouring over the edge. If pouring over the edge, you'll see
faster deterioration in your roof shingles. I make a point to go out during rainstorms if I can to watch for clogging.

If you've ever cleaned gutters, you'll find in addition to leaves and such, you'll find little shingle particles. So as the shingles deteriorate, little bits of them come off and collect in the gutters. You might see lots of little bits of shingle directly in the gutter above the garage door and just below the darker area. This can help to affect the colour of the shingles.

There may be a different reason for your darker shingles, but I suggest this only because it looks like the darker area is directly below the upper roof. Sometimes you can look around the neighbourhood and see other people where the roof is failing in specific areas just because that part of the roof is being bombarded with too much water.

thanks daylily. It is in a line right under the eaves troughs but we regularly inspect he eaves and they are clear of leaves. I wondered if it might be overflow of water or even that it is a shady location but I see it on all kinds of houses in the neighbourhood with the same roof style. So I think you are right it is probably overflow of heavy rain wearing away the shingles. Ill keep a watch

Did not read all.

I agree full soffit and ridge vent.

I agree say no to power attic fans. They sound like helicopters on your roof. Unless you like helicopters on your roof... Not to mention the pulling conditioned air out of your house into the attic, that is a whole nother problem.

To flygirl519 - sometimes even if the eavestrough is clear, there is a blockage in the vertical pipe going from the upper roof to the lower roof. We always take the water hose up there and run water down to make sure that the pipe going down isn't blocked. If blocked, we spray water to try to clear the pipe as sometimes this can dislodge the debris.

Hi, I am the OP :-) I have had the roof replaced with architectural shingles and have had 3-fin vents installed with about 50% more venting capacity :-) So far so good, but I notice that the metal flashings have been installed a bit differently than before. Previously, all metal was on the shingles, and now some shingles are on the metal. I wonder if it has been installed correctly?

That is done correctly.