I’ve run into that same paperwork headache—my last project was just a lightweight tray system, but the city still wanted a full set of drainage calcs and a stamped plan. I tried to handle the calculations myself at first, thinking it’d be straightforward since the roof pitch was gentle and the load minimal. Turns out, the inspector flagged my hand-drawn diagrams and asked for an engineer’s stamp anyway. Ended up paying for a consult just to get the official sign-off, which felt like overkill for such a small install.
Funny thing is, I’ve seen neighbors do way more ambitious stuff without anyone batting an eye... seems like it all depends on who’s reviewing your permit. The inconsistency is wild. I get why they’re strict—one bad drainage setup and you’re looking at leaks, rot, or even structural issues down the line—but there’s got to be a better way for small projects.
If you’re in an area with heavy rainfall or clay soil, I’d say err on the side of caution and get the pro involved early. Otherwise, you might get lucky with a detailed DIY plan, but it’s a bit of a gamble.
I get the frustration, but honestly, requiring stamped plans—even for lightweight tray systems—makes sense from a liability standpoint. Inspectors can’t always judge structural or drainage adequacy just from a DIY sketch, no matter how straightforward it seems. I’ve seen “simple” installs cause major issues when overlooked details like overflow routes or membrane compatibility get missed. The inconsistency between projects is annoying, but I’d rather deal with red tape than risk water damage or structural failure down the line. Sometimes the upfront hassle is just the price of playing it safe.
