# HVAC curb detail



## llmotoll (Feb 27, 2015)

Guys in our office always seam to debate back and forth which detail is best to use on a HVAC curb. Specifically on the top of the curb wall flashing any type of EPDM, TPO or PVC roof.

Option 1- utilize the wood nailer that comes with the curb and terminate the top of wall flashing with counter flashing

Option 2- remove the wood and increase the thickness of insulation on the wall to (usually 1.5") match the top of curb flange and wrap the membrane up and over the top of the curb to eliminate the need for counter flashing.

Which detail do you guys use? 
Which is better? Why?


----------



## 1985gt (Dec 21, 2010)

I prefer up and over. It eliminates what could be a wind blown odd ball leak.

With that being said our work consists of about 90% reroofs. The owners never have the budget to lift every unit so most of the time we wrap it up, waterstop, term and counter flash.


----------



## Grumpy (Oct 29, 2008)

Up and over when ever possible. I think it is not only better, but on build outs and new construction is much faster. 

I bid alot of curb build outs and always insist on factory insulated curbs FWIW. On an existing roof you are kid of stuck with a slip metal counter flashing unless someone is paying me to lift the units off the curbs.


----------

