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What is a Cedar Conversion?

Updated on December 4, 2015

Twenty Years Later

Twenty years will pass and the life of your cedar roof will be over and it will be time for a new roof but when you see the cost of labour for a cedar install you realize that for the same price you can get an asphalt roof.

So yes a cedar conversion defined is when you have a cedar roof and you then get an asphalt roof replacement.

Why would you do this? The cost of the replacement is almost the same but this is all about planning long term as for roof number three will be much more affordable.

Here is Why

A cedar roof does not actually sit on a roofing deck. All that is required to install a cedar roof is strapping which is a strip of wood running horizontally from the eave to the ridge which has a space between the strapping several inches apart depending on the builder.

Asphalt roofing material cannot sit directly on strapping and needs a solid plywood deck. The cost to install a plywood deck is quiet an addition to a roof project but is a huge asset in the future when it is time to replace your roof as anything can sit of plywood even if you choose to go with a new roofing material that is not asphalt.

The other bonus for the average home owner is that they do not have to worry for a little bit longer as the warranties of asphalt compared to cedar speak for themselves. Do not get me wrong a cedar roof can come with a pretty strong warranty if you get an old growth three quarter inch resawn shake. If fact there are roofing companies around the Lower Mainland of Vancouver that will offer a fifty year roofing warranty with a resawn cedar shake that has been treated. But the average affordable shake used in new construction comes with a lifespan of about twenty years.

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Now Lets Talk Asphalt

Asphalt on the other hand comes with a thirty year warranty if you start with the most affordable and from there the warranties only go up, all the way to lifetime. The oil based product has a much more resilient build to the elements than its cedar counterpart. There is also competition in the visual street appeal when it comes to the capping, cedar used to dominate the market with this feature.

Asphalt manufacturers have been working hard as trying to resemble the beauty of the raised cedar cap by manufacturing really thick, and visually appealing capping which resembles cedar. You do get more colour choices with asphalt shingles with different designs some even trying to imitate the visual effect of cedar shingles and shakes. compared to cedar speak for themselves.

The Cedar Conversion

Cedar shake or shingles sit on strapping
Cedar shake or shingles sit on strapping
In a cedar conversion plywood is required for the asphalt deck
In a cedar conversion plywood is required for the asphalt deck
The ice and water shield, underlay and then shingle is installed onto the house
The ice and water shield, underlay and then shingle is installed onto the house

Things to Watch Out For!

When you get a cedar conversion done there are two major structural changes to your home that must be factored in and taken care of. Cedar shake has an amazing ability to breathe on its own but when a plywood deck is placed down the entire attic is tightened up and the ability for moisture to escape the home is decreased dramatically.

Vancouver roofing companies are well aware of the need for roof vents but you may be surprised to find out that a few do not install enough to meet code or follow the roofing material manufacturer’s recommendations.

Educating yourself on what is required to have a well ventilated roof is not hard and any person who can do basic math can figure out how much roof vents will be adequate on their home. This is absolutely fundamental as it must be done during a cedar conversion and if it is not then you may be in for higher energy usage in your home and a roof that does not last as long as you intended, new roofing plywood deck included.

Click here to help working out how many roof vents you may need

Should I Convert?

Roof Type
20 year - 50 year
Curb Appeal / Reuseable
30 year - lifetime
Colour Choice / Affordable

One More Thing...

The other important factor of a cedar conversion is that the new plywood deck will raise the height of the roof by three eighths to half an inch up. I know this does not sound like a lot but there are certain elements of the home that may not have been designed for such a change. The main weak point may be the flashing on the roof. Flashing is the metal pieces on the roof that protect the home from water finding a way into the attic by running down the chimney or the various pipes on the roof. Flashing also runs along a wall where the roof may run into or along as well as skylights. If the roof is raised that line that the flashing sits will have to be raised too. Most homes are fine with this change but a few are required to replace the chimney counter flashing which is mortared in, or cut the siding if the deck butts up higher. This is not common but does occur.

The other important change is the exposed plywood deck along the gable / rake edge. Like the flashing issue when the plywood is laid down the raised deck will exposed on the gable edge. In the rainy Pacific North West this can be a issue as plywood does not like rain so it is very important for the roofing contractor to install flashing along the gable to ensure that the edges of your new roofing deck is not exposed to the elements.

Check out this great video on cedar conversions thanks to SPR-Canada Roofing

Special Labour Required

When hiring a roofing contractor it is important that you sign up with one who has experience in cedar conversions. This is a little different than the standard roofing replacement as it will require an individual who is handy with a table saw. The various angles of the valley and other items that might stick out of the roof will require someone who can measure and cut the plywood without making many mistakes.


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