# Pitched roof with trusses over tar and gravel



## shane.nesbitt (May 26, 2007)

I have a free standing garage which has a tar ang gravel slightly pitched fron to back roof. I want to replace this roof with engineered trusses due to leaks and for cosmetic value. Can I add trusses on top of the old roof by shimming up the back so that it is level? The walls are in fairly good shape....


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## Ed the Roofer (Jan 27, 2007)

You can if an architect/engineer and/or buillding code official approves it. Either way, you have to get it drawn up and approved first unless you live in an area without code enforcement, which is there for your protection and safety.

Ed


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## Gerry Kiernan (Apr 23, 2007)

*Pitched trusses over tar and gravel*

Hi 

Along the same vein, I have a large shop with basically flat tar and gravel roofing. I have some leak issues, and have received a ballpark figure to completely replace the roof with torch on membrane. The cost would be about $25,000 Cdn. The shop is about 4200 square feet. I am going to look into the costs of putting up supporting low pitch structures, and roofing with metal. This way I could leave the flat roof in place, and do the work over a period of time. Would anyone care to offer an opinion or advice on this scheme? Is it sound, or hairbrained? Has anyone done cost comparisons between the two methods?

Thanks

Gerry


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## Ed the Roofer (Jan 27, 2007)

If it is financially feasable, then by all means, create a pitched roof over the existing flat roof.

I don't know how much $ 25,000.00 Canadian equates to in US dollars, but if it were equal, that seems way too expensive on its own merit, but I do not fully appreciate the potential difficulty factors involved or how cut up the roof sections are.

The worst thing about the low slope, also known as flat roofs, is that as they building weight settles, the main framing areas do not. This inevitably creates pockets of standing water, and afer a long enough period of time, leaks are created and intensified from prolonged submerssion.

Open up the flat roof after the pitched roof is completely on, to allow for an open air attic cavity to breath. Some ventilation theories I have studied, contradict the normally accepted practice, especially in the colder Canadian climates.

Ed


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## Gerry Kiernan (Apr 23, 2007)

Thanks for the input Ed

Currently, our dollar is at about 92 cents worth of your dollar, so in your terms we are still looking at about $23,000. As far as the ventillation goes, my idea was to use pitched roof with no hip style ends, so I could close off the ends of each section with ventillated soffit type material, or screening to keep out birds and bugs, but allow the support structure to be completely dry. The entire roof is composed of three sections, each of which is about 24 feet wide, and range from about 40 feet to about 60 feet long. They parallel each other, so I could do the roof one section at a time, starting with the worst problem section. One issue I have to deal with is that the workshop is under numerous fir trees, and that means an accumulation of needles. I will have to put some kind of clean out trough between section one and two, and between section two and three. I am thinking fairly heavy galvanized steel, formed into a vee, with a flat base, about one foot wide, so I can walk along it and rake out the accumulation.

I still have to do a cost effectivity study to see if the idea is practical, but as I live on the Wet coast of Canada, with about 40 inches of rainfall a year, I do not think flat roofs are very practical. I think in the long run I would have better reults with a pitched roof and metal.

Gerry


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## Ed the Roofer (Jan 27, 2007)

You are absolutely dead right on by going with a pitched roof instead of a flat roof with those conditions.

But, a well installed standing seam or batten seam roof is made practical and possible only by the integrity of the little detail work, such as many, many styles and types of flashings and accessories.

Any semi-trained monkey can install the panels and the clips. 

*( Sorry to any actual Monkeys I have offended out there. )* 

When the vertical panels start to run just a little bit out of square, it will throw off every subsequent panel, unless you know how to prevent this from occurring in the first place or how to correct it if it has already begun unnoticed.

Ed


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## Gerry Kiernan (Apr 23, 2007)

I'm just going to go into the corner and eat my banana.

Gerry


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