This was a job in Carson Ca. The warehouse was getting new offices and needed new heat pumps on the roof. These rooftop heat pumps are installed on metal factory curbs that must be level. We need to modify the roof to accept these curbs and hold them strong and level.
These installation are done by laying out installation locations with the HVAC installer. Typically the equipment installer will have a metal roof curb laid in the location the unit will need to be installed.
After we know our new rooftop location we drill a pilot hole and layout a platform that will be bigger than the supplied curb so we can land as much of platform support onto the roof framing structural.
We then layout or roof demo about 12″ beyond the the platform area and have some demo guys clear our roofing down to the wood. Using our pilot hole we layout the opening for our new plenums and cut the roof sheathing out. This plenum opening gives us access to above and below the roof from a scissor lift or scaffold below.
These are two sets of roof platforms designs for the same job. The solid 4″ x 16″ is best when you are prepared and have the lead time to order it. Because it can be ripped and installed quicker than framing miniature parapet walls which will also need blocking etc.
After the platform side walls are framed and sheathed we install a variety of joists beam stiffeners etc to support the metal factory curb above. The top is also capped with plywood sheathing and the roof curb is left sitting on top.
The equipment installers will come and screw down the factory curb to the platform and then the roofers will come and roof the structure in. Sometimes roof crickets are needed and maybe installed by the carpenter or the roofing company.