Flat roof replacement and plumbing codes

[jar546]

At what point, if at all do you require the plumbing code to be addressed during roof replacements?

For example:

Existing roof, built up with ballasts is being replaced right down to the decking including some of the rotted decking. It will be replaced with a new edpm over insulation board that meets the energy code.

The entire roof is surrounded by parapets with no scuppers and no secondary drains but has been "working" for the past 25 years. Do you address the IPC requirements or not?

 

[Paul Sweet]

It's more a structural issue than plumbing. If the new insulation has a higher R-value the roof loading could increase because the snow won't melt as fast. If the new insulation provides a 1/4" slope, then water might be able to pond to a depth that would exceed the structural capacity of the roof before running over a high spot to an adjacent drain.

On the other hand, if the old roof was well insulated and drains were close enough together to allow water to get to another drain if one got clogged, then there might not be a danger in not adding overflows. Also, an adhered membrane won't weigh as much as a ballasted built-up roof.

 

[jar546]

Great thought Paul. I never thought of the fact that since it is now an insulated roof, it will hold snow longer. I was only looking at the fact that the roof will be lighter without the ballasts and heavy tar layers. Thanks for the lightbulb moment.