Most model codes provide that if gas piping is run within the building envelope, the joints must be welded. If it is run on the rooftop, threaded joints may be used. There are significant cost differences in the two methods–threaded joints being much more economical. It is also much easier (less labor-intensive) to install gas piping on a rooftop, than overhead within a building. For this reason, gas piping is often roof-mounted.
Once again, here comes the wood blocking–used to shim the piping above the panel seams. In the picture, you can see the long-term effects of wood blocking on coated steel roofs. Warranties are voided. To keep the piping from migrating on the roof, all kinds of nasty things are done to the new roofs–most of them involving the punching of holes in the panels and (temporary) externally applied sealants. The result is leak problems, repeated maintenance and warranty violations.
The S-5! solution: Gas piping is mounted above the panel seams using S-5! clamps.
No wood blocking.
No impediments to roof drainage.
No holes in the panels.
And with S-5!–it's no sweat!
This close-up shows how a small piece of "Uni-strut" and a pipe clamp were used to facilitate the installation. Electrical conduit is mounted in a similar fashion.