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Cedar roof replacement

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[OP]
Jr. Member
Oct 21, 2017
171 posts
16 upvotes

Cedar roof replacement

The roof is about 27 years old. There are no leaks.

How do you tell when the roof should be replaced? Do you wait until there is a leak inside the house or that is too late?

The condition of the roof is similar to this youtube video How to walk on a wood shake roof; where to step without breaking the shake.

If you are converting the cedar roof to asphalt, plywood needs to be put in. Can the structure of the house handle the weight of all the new plywood and asphalt singles or do you have to go with a new cedar roof and not asphalt to be on the safe side?
7 replies
Sr. Member
Oct 22, 2016
724 posts
612 upvotes
Comox Valley
curiousgeorge1000 wrote: The roof is about 27 years old. There are no leaks.

How do you tell when the roof should be replaced? Do you wait until there is a leak inside the house or that is too late?

The condition of the roof is similar to this youtube video How to walk on a wood shake roof; where to step without breaking the shake.

If you are converting the cedar roof to asphalt, plywood needs to be put in. Can the structure of the house handle the weight of all the new plywood and asphalt singles or do you have to go with a new cedar roof and not asphalt to be on the safe side?
27 years is old for a cedar roof. If you were on the BC South Coast, I would suggest replace it, due to rot. Other parts of the country, I do not know how longer they would last, if it was a drier environment. Where are you located? Maybe someone else would have a better idea, on how long cedar would last there. But as you state, your roof is like the YouTube video you posted, while that roof should be replaced. It is in bad shape.

If you are concerned about leaks, go in your attic (if you can) during a rainstorm, to see if you have damp spots on underside of roof.

The structure of the roof can easily handle the plywood and new shingles. Due to cedar roofs, having strapping so close together, 3/8” plywood is used instead of a thicker plywood. 3/8” is quite light. BUT the cost of plywood/lumber is so high, if it could be put off for a year, I think you would save a nice $
[OP]
Jr. Member
Oct 21, 2017
171 posts
16 upvotes
User452441 wrote: 27 years is old for a cedar roof. If you were on the BC South Coast, I would suggest replace it, due to rot. Other parts of the country, I do not know how longer they would last, if it was a drier environment. Where are you located? Maybe someone else would have a better idea, on how long cedar would last there.

If you are concerned about leaks, go in your attic (if you can) during a rainstorm, to see if you have damp spots on underside of roof.

The structure of the roof can easily handle the plywood and new shingles. Due to cedar roofs, having strapping so close together, 3/8” plywood is used instead of a thicker plywood. 3/8” is quite light. BUT the cost of plywood/lumber is so high, if it could be put off for a year, I think you would save a nice $
House is located in Vancouver. Google Search says cedar roof could last anywhere from 30 to 50 years depending on thickness and quality. Majority of the sources say around 30 years. There is no wood rot (wood is not soft at all).

What do you mean by cedar roofs strapping so close together and that 3/8" plywood is used instead of thicker plywood? Is there a disadvantage to using less thicker plywood as in that affects the longevity of the roof? Meaning I need to replace the wood in say 15yrs instead of say 30yrs?

Does 3/8" plywood support 3 tab asphalt singles (15-18yr lifespan) and architectural asphalt shingles (24-30yr lifespan)?
Sr. Member
Oct 22, 2016
724 posts
612 upvotes
Comox Valley
curiousgeorge1000 wrote:

What do you mean by cedar roofs strapping so close together and that 3/8" plywood is used instead of thicker plywood? Is there a disadvantage to using less thicker plywood as in that affects the longevity of the roof? Meaning I need to replace the wood in say 15yrs instead of say 30yrs?

Does 3/8" plywood support 3 tab asphalt singles (15-18yr lifespan) and architectural asphalt shingles (24-30yr lifespan)?
As per the photo enclosed, when you install a cedar roof, it uses strapping that is close together, instead of further spaced roof trusses. Plywood would have the same life span, regardless of what shingle you put on top of it.
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Deal Fanatic
Jul 7, 2017
6664 posts
2998 upvotes
SW corner of the cou…
curiousgeorge1000 wrote: What do you mean by cedar roofs strapping so close together and that 3/8" plywood is used instead of thicker plywood? Is there a disadvantage to using less thicker plywood as in that affects the longevity of the roof? Meaning I need to replace the wood in say 15yrs instead of say 30yrs?
Roof material (shingles, ply) isn't that heavy compared to the potential snow load.. I have concrete tiles and the strapping is every 30cm.
I smile when I see container ships sailing past my house laden with stuff made in China
[OP]
Jr. Member
Oct 21, 2017
171 posts
16 upvotes
User452441 wrote: As per the photo enclosed, when you install a cedar roof, it uses strapping that is close together, instead of further spaced roof trusses. Plywood would have the same life span, regardless of what shingle you put on top of it.
What is the thicker plywood in inches? Is the less thicker 3/8" plywood a problem with the plywood at risk of collapsing when there is snow on the roof?
Sr. Member
Oct 22, 2016
724 posts
612 upvotes
Comox Valley
curiousgeorge1000 wrote: What is the thicker plywood in inches? Is the less thicker 3/8" plywood a problem with the plywood at risk of collapsing when there is snow on the roof?
1/2” or 5/8” plywood is used at times when roof trusses are used. It is not used when you have a cedar roof coming off, 3/8” plywood instead.

Zero concern in roof collapse of heavy snow load using 3/8”, in your situation. Keep in mind the support of your roof is very high, with the amount of strapping on it.
[OP]
Jr. Member
Oct 21, 2017
171 posts
16 upvotes
User452441 wrote: 1/2” or 5/8” plywood is used at times when roof trusses are used. It is not used when you have a cedar roof coming off, 3/8” plywood instead.

Zero concern in roof collapse of heavy snow load using 3/8”, in your situation. Keep in mind the support of your roof is very high, with the amount of strapping on it.
Very good info, thanks!

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