Trane recommends that the roof curb be placed directly on the roof support members and welded into place.
Roof curb installation detail.
Roof curbs should be supplied by the hvac manufac.
Installing curbs that rest in the flat lower panel area of metal roofing invites water tightness problems since the curb now has to be installed and sealed in the most vulnerable area the surface where rainwater flows.
If the roof curb will be mounted on a new building it can be assembled at any convenient location and installed as soon as the roof support members are in place.
As a general rule the curb should be placed directly on the roof support members.
The curb can also be mounted on a roof deck.
A good penetration requires.
Do not overlap counter flashing over the top of the roof curb.
Contractors should not be asked to supply or install roof.
Curbs should be sloped to avert water ponding.
If the curb is mounted on the roof deck additional support is necessa ry directly below the curb flanges to minimize vibration.
Pressure treated nailers should be provided by the curb manufacturer to receive roofing felts and eliminate noise transfer.
Curbs should be a minimum of eight inches above the finished roof and factory insulated to reduce condensation.
Install roof curbs rib to rib.
Turer to the general contractor or building manufacturer.
A canted curb for example should be used for a built up or modified bitumen system roofing system.
And installed by an experienced erector.
First the basic design of the curb should take into account the roofing components so that it can be properly flashed into the roof system.