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HVAC Forums => HVAC Help => Topic started by: Sergroum on April 24, 2018, 10:12:48 AM

Title: Rooftop installation and roof reinforcement
Post by: Sergroum on April 24, 2018, 10:12:48 AM
Hello, hello.

I am having difficulty finding the appropriate information, I wonder if you could help me guys. At what point does one need to reinforce the roof to install a heavier rooftop unit? Let's say I currently have a 5 ton unit and I want to increase it to 8 ton. The weight going from 577 to 900s. Would I need to have that curb reinforced from below? What about from 7.5t to 10t. Is there any way I could find information what weighs require what? Anyone faced this issue before?
Title: Re: Rooftop installation and roof reinforcement
Post by: rmuntz on April 24, 2018, 01:47:54 PM
You would need to get an engineer involved.
Title: Re: Rooftop installation and roof reinforcement
Post by: Admin on April 24, 2018, 03:38:38 PM
I don’t think 300 pounds would matter one way or the other.   The roof would have already been designed to handle a “large” service technician.
Title: Re: Rooftop installation and roof reinforcement
Post by: Sergroum on April 25, 2018, 12:30:03 PM
What are the usual reasons why rooftop units are leaking water when it's raining anyway? I dont mean condensate pan clogged up, but exactly due to the rain. I see it so often. Not too long ago, York's own warehouse in oakville got flooded. Why does it happen? The installer failed to tape up the edge of the curb when laying the unit down? The weight of the unit vibrated the rooftop into causing cracks? Any ideas?
Title: Re: Rooftop installation and roof reinforcement
Post by: rmuntz on April 25, 2018, 12:49:25 PM
I agree with the 300 pounds not being an issue, except that the 300 lb service guy is not up there 24/7 (hopefully). Also, now you have the extra 300 lbs of the unit plus the 300 lb service guy. In most cases there would be no issue, my point is, if there is any doubt about the integrity of the roof structure, that's not a call that we make.

As far as the roof leaks go; a roof should not leak if the curb is installed correctly (by a roofer) and the unit is installed correctly. If the gas, electrical or stat wire are put through the bottom of the compressor section, or put through the side of the curb, they will leak. P traps are also critical and access panels should have all screws in them. I've found access panels laying on the roof in the middle of the winter (why is my gas bill so high?). Remember, with a leaking membrane roof, the leak might be 50' away and travel through the roof.
Title: Re: Rooftop installation and roof reinforcement
Post by: Sergroum on May 25, 2018, 03:09:33 PM
Has anyone ever encountered this matter before? Increasing tonnage from 5 ton to 8 ton let's say. Granted, the ductwork will be out of whack. But has anyone ever been concerned about the roof bracing itself?
Title: Re: Rooftop installation and roof reinforcement
Post by: Porcupinepuffer on May 26, 2018, 07:24:06 PM
As rmuntz said, it would be up to an engineer/builder to really know if the roof is fine for the extra weight. It's way out of our scope to assume if it is or isn't... If a change of the original plans to something of a heavier weight makes you uneasy, get something in writing that clears you of any liability for the extra weight to show you mentioned it as a possible issue.