Commercial building roofing insights

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SonomaCat
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Commercial building roofing insights

Post by SonomaCat » Thu May 21, 2009 10:30 am

Okay, this is yet another post from me hoping to tap the knowledge of Bobcatnation.com to educate me on one of the many, many topics on which I am completely clueless. Today's topic: Roofing.

So we are looking at a dowtown-esque building that has one of those flat tar kind of roofs on it, and apparently it's not a particularly good roof. Building inspectors have said the roof should be "replaced" and the quote for such work is $30K.

I have also been told that a neighboring building recently decided to use an overlay system instead of replacing their roof, and that the cost was less than half the cost of replacing the roof. This overlay is said to come with a lifetime guarantee from the manufacturer.

A couple questions ... first, when they say the roof needs to be "replaced," exactly what does that mean? Does that go all the way down to the structure of the building, or is it just removing the old tar and putting new tar and materials in?

And second ... does anyone have any insights or experience with overlay type of systems? Is it reasonable to go that route as opposed to replacing the roof, or is that just a bandaid solution that won't really fix the problem?



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AlphaGriz1
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Re: Commercial building roofing insights

Post by AlphaGriz1 » Thu May 21, 2009 12:44 pm

I am not a contractor but I would say get rid of a flat roof 100-100 times.

The design is built to leak hold heavy snow loads and cost you money over and over again for many years to come. (See 4 Seasons Arena in GF)


I would spend the money to add any type of pitch to the roof I could. (Min of 4/12 or 5/12)

I would also guess that for $30K they were going to replace the whole thing and make it a pitched roof. Just a guess.


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Re: Commercial building roofing insights

Post by SonomaCat » Thu May 21, 2009 1:10 pm

Thanks, Alpha. I'm pretty awful on the technical terms with this, but I do believe the roof has some slope to it right now (higher in the front than the back, so the water runs toward the back of the building. I have no idea what ratio the slope is, though. Is that what you mean when you say "pitched," or are you talking about an upside down V-shaped structure to force the water to run down the sides?

It's kind of embarassing to discuss a topic I know so little about ... thanks to everybody for withholding to mockery (so far :wink: ).

The footprint of the building is about 4,500 square feet, just for background.



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Re: Commercial building roofing insights

Post by SonomaCat » Thu May 21, 2009 2:12 pm

Okay, ten minutes of googling has helped me ask a little better question ... does anyone has any insights into the benefits/drawbacks of using this product:

http://www.duro-last.com/generalContent/flat-roofs.asp



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Re: Commercial building roofing insights

Post by Bleedinbluengold » Thu May 21, 2009 10:51 pm

I'm disappointed, BAC. You of all people know that this is all the rage in urban roofing.

http://www.worldchanging.com/archives/004890.html" onclick="window.open(this.href);return false;

Such designs are actually gaining traction in Chicago I'm told.


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Re: Commercial building roofing insights

Post by SonomaCat » Fri May 22, 2009 12:22 am

Bleedinbluengold wrote:I'm disappointed, BAC. You of all people know that this is all the rage in urban roofing.

http://www.worldchanging.com/archives/004890.html" onclick="window.open(this.href);return false;

Such designs are actually gaining traction in Chicago I'm told.
Yeah ... I don't think Lewistown is urban enough to need to put grass on roofs quite yet. Maybe when the next million people move there. :wink:



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Re: Commercial building roofing insights

Post by BobCatFan » Sat May 23, 2009 11:01 pm

According to my brother, who works in the commercial construction trade, that new white rubber membrane roofing material is the best roofing material available. He had it installed on my mother's home and finally, the roof stopped leaking as the roof had leaked since that addition was put on in the early 1960's. I was up on the roof a few months ago, it still looked good after 7 years or so.

You may have to tear off the old layers of black tar roof material. That roofing material is very heavy and I doubt if it had every been done before due to the cost. Now you are the lucky one.



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Re: Commercial building roofing insights

Post by BobCatFan » Sat May 23, 2009 11:05 pm

BAC
While your are doing the tear off, you should lay down 8-12 inches of foam board. Those old buildings will not have any insulation in them.

In the end, it will be cheaper to build new.....



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Re: Commercial building roofing insights

Post by SonomaCat » Mon May 25, 2009 12:26 am

Thanks for the insights, BobCatFan. Appreciate it.



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Re: Commercial building roofing insights

Post by mslacat » Tue May 26, 2009 3:34 pm

I believe the white roofing is a "TPO Roofing" system which is a totally different system that is what is typically thought of when people think of flat roof system. I can not think of any project I have been involved with in the last 15 years or so that has failed. The most common problem I have seen are leaks due to in proper flashing at penetrations (hole where duct/vents come through the roof) or at edge flashing. I have never seen a failure in the material itself. The TPO roofing they are installing now is even better than what they were putting in 15 years ago. All edges are "welded". The material is a composite with fiberglass reinforcing, it is white so that it reflects heat and light(which typically is the hardest thing on the roofs). It stands up to brain dead mechanical repair men, better than anything I know

If you budget can afford it use a TPO roofing system. Once you install it you can forget it for a very long time. The "overlay system" - if it is what I think it is, will work for a while but will not nearly as long as the new roof. One more thing to think of is that by code, you can only overlay a roof once, and then it is rip the entire roof bare to sheathing (wood decking), and that can add to the expense down the road. Check to make sure the roof has not been overlayered once ( or more times) before.

As always make sure you get quality/licensed roofer/contractor especially if you are overlaying. Nothing can cause a problems like a leaking roof.



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Re: Commercial building roofing insights

Post by St George » Fri Jun 09, 2017 11:18 am

First off, try to determine how many layers of roofing are on the building now.
Second, how is the roof drained at the present time? To the edge with gutters? or to the center with roof drains?
Now for the new roof. adding a sloped roof will require a structural engineer to look at the entire building to determine if it is fit to add that much weight.
As far as flat roofs you have a few options.
There are a few membrane roofs, EPDM, Etc. and of those there are different ways to attach them, fully adheared? mechanical fasteners?
Modified Bitumen or "torched down" is reasonable priced and for the money is not a bad option.

Just a little info from the depths of my beer soaked brain for what it is worth.



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Re: Commercial building roofing insights

Post by St George » Wed Jun 14, 2017 10:01 am

Just a couple more things to think about:

1. If tearing off the old roofing material does it contain asbestos?
2. When installing new roofing material, are there mechanical (heating and cooling) units on the roof. A lot of contractors will roof up to them creating a great spot for leaks. The units should be lifted and roofed under or properly flashed to prevent leaks.
3. If you go to a sloped roof and have to relocate the mechanical units up to the new roof surface, code requires a work access platform around the units.



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