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stuwithau 07-05-2006 02:19 PM

Michigan code regarding roof over
Does anyone know the Michigan code for a "roof over"?

My roofer told me that he only does tear-offs because it's the code. There's only one layer of 3-tab shingles on the roof now but they're failing and dropping gravel all over (no leaks - yet).

I know it's a better approach but I'm working to a tight budget.

AaronB 07-05-2006 03:48 PM

Tearing off should be code. I do not know the code in Michigan, but roofing over will cut the life of your shingles in half. Generally a bad idea if youre looking to save money.

MJW 07-05-2006 04:48 PM

The new IRC 2006 states no overlays for contractors. It is legal for the homeowner, but not a contractor. Be prepaired for leaks and a short life on your shingles with an overlay. Especially with the situation you describe.

manhattan42 07-05-2006 06:36 PM

No Such Requirement

Originally Posted by stuwithau
Does anyone know the Michigan code for a "roof over"?

My roofer told me that he only does tear-offs because it's the code. There's only one layer of 3-tab shingles on the roof now but they're failing and dropping gravel all over (no leaks - yet).

I know it's a better approach but I'm working to a tight budget.

Michigan Code, which is the 2003 International Residential Code, has no such mandatory requirement to rip off a roof before reroofing either under the 2003 version of the Code or the new 2006 version.

The roofing contractor is making up stories.

You can see Michigan Code online here:$vid=icc:mi

Click the links in the left column for Residential Code then Building Planning. Chapter 9 section R907.3 allows re-roofing except:

"1) Wherethe existing roof or roof covering is water-soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.

2) Where the existing roof covering is wood shake, slate, clay, cement or asbestos-cement tile.

3) Where the existing roof has two or more applications of roof covering."

The only difference between the 2006 version of the IRC Code and the 2003 is that the 2006 version adds a 4th exception:

"4) For asphalt shingles, when the building is located in an area subject to moderate or severe hail exposure according to Figure

Unless local ordinances have stricter regulation on roof recovering, what you have been told is wrong and both the IRC 2003 and 2006 expressly ALLOW for roof recovering and there is no requirement to rip off an existing roof except where one of the three exceptions above are present.

Manufacturers will warrant any roof re-covering for as long as they warrant shingles that are applied over a new surface.

While ripping off the roof will no doubt give you the better job, many roofing contractors misrepresent the facts about permitted roof proceedures just to make you spend a few bucks more when it is completely unecessary.

Given the condition of your existing roof, however, your code official might not issue you a permit for a roof recovering citing exception 1 above.

Ultimately it is the code official's call. You should get his input before deciding one way of the other.

MJW 07-05-2006 06:44 PM

The code in MN was changed to make tear offs a must when they adopt the code. Michigan may be different, but I would look into it before calling someone a liar.
As far as I'm concerned it is neccessary to tear off existing shingles.

stuwithau 07-06-2006 09:59 AM

Roof over
Thanx for the feedback. Interesting that this thread echos what I'm finding all over the web that there is a debate about whether the old roof "needs" to be removed.

Can anyone explain why this would shorten the life of shingles and/or cause leaks? I have yet to hear a good explanation.

Just for the record, I accept that this sounds logical for better workmanship, but I am a mechanical engineer and would like to "understand".

manhattan42 07-06-2006 07:46 PM

I am not of the school that thinks that roofs must be stripped before re-roofing.

Nor are any of the major model building codes or shingle manufacturers.

Roof manufacturers warrant their products fully when used for cover overs for the same duration of time as they do with a new installation warranty.

I have also in 30 years in building and code enforcement never observed these claims that your roof shingles will only last half as long when applied to existing roofs when done properly. It may be true in some locations but certainly not true in mine. Roof shingle cover overs work properly and well when installed within the parameters of the building codes and manufacturers installation instructions. Failure occur when code and manufacturer guidelines are ignored or shodd workmanship is employed.

Existing roofs currently failing with nails popping up or water damaged structural sheathing or severely curled shingles should not be covered over and cannot be covered over by code or manufacturer's installation instructions. Such installations can result in new shingle layers not being fastened properly, not sealing properly...can result in lifting allowing ice damage or water and wind penetration.
Loose fasteners in layers underneath can cause holes in upper shingle layers. Etc...

There are also limits to the dead and live loads from too many layers of shingles a framed roof can bear, which you as an engineer surely can understand.

Otherwise, I have done scores of roof cover overs in my career with no problems and have not seen the alleged kinds of failures that others are claiming. I therefore do not share the opinion of those who insist that ripping off every layer every time should be a mandatory code requirement...but I still respect those contrary opinions.

In my view, the current code allowance for reroofing cover-overs within reason is prudent and correct. It bases the ability to recover on actual conditions of the roof and not some arbitrarily prescribed method.

That said, ripping off to the structural sheathing will provde the best job, but a complete rip off is not always warranted nor will provide you with the best return for the investment.

stuwithau 07-07-2006 08:30 AM

Thanx for the clear thoughtful responses. I have what I need to make a decision.

jwroofing 07-21-2009 01:14 PM

it seems like you definitley have a problem that needs fixing. A roof is allowed to be shingled over if you only have one layer on the decking and if the existing shingles are not curled up all over the roof a lot of roofers will tell you diferently but they are wrong and probably not very good roofers anyways. if you do get a re-roof do not let them put on any underlayments because that will automatically void any warranty by the manufacturer. if you have any questions feel free to reach us at and ask for adam.

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