I’ve had those mats do the slow crawl myself—on a mild pitch, mind you, nothing wild. I tried using landscape pins at first, but they ended up poking through the membrane, which made for a fun spring leak. What finally worked for me was edging the mats in with pressure-treated 2x4s and adding some heavy pavers here and there. Not perfect, but at least the plants aren’t all huddled at the bottom anymore...
That slow crawl is no joke—seen it a few times during inspections, especially on roofs with just enough pitch to make things interesting. I’ve watched folks try everything from chicken wire to those plastic grid systems, but the 2x4s and pavers seem to be the most reliable, at least short-term. Curious—did you run into any pushback from your local building department about using pressure-treated lumber up there? Some places around here get picky about what touches the membrane.
Curious—did you run into any pushback from your local building department about using pressure-treated lumber up there? Some places around here get picky about what touches the membrane.
- Haven’t had direct issues with PT lumber yet, but I’ve heard stories. Around here (midwest), inspectors seem more worried about chemical leaching than actual weight or structure.
- On one job, they made us put a slip sheet between the PT and the membrane. Kind of a pain, but it passed. Not sure if that’s standard everywhere.
- The plastic grid systems you mentioned—those are getting popular, but I’ve seen them warp in hot summers. 2x4s and pavers just feel sturdier, even if they’re not “officially” approved for long-term use.
- Did you have to submit a full assembly detail for your green roof? Our city started asking for cross-sections showing every layer, even for small projects. Wondering if that’s just a local thing or if it’s catching on elsewhere.
We had to do the full assembly detail too, even for a tiny 200 sq ft section. It felt like overkill, but I get why they want it—too many horror stories about leaks and failed membranes. The slip sheet thing is definitely a thing here (Chicago area), and honestly, it’s not the worst extra step if it keeps the inspector happy. I’m with you on the plastic grids... they look slick at first but I’ve seen them buckle after a couple hot summers. I’d rather deal with the weight of pavers than risk a warped mess down the line.
I hear you on the plastic grids—looked great on install, but I’ve seen them get wavy too, especially on south-facing roofs. The pavers are a pain to haul up, but at least they stay put. Curious if anyone’s tried those newer recycled rubber tiles? I’ve only seen them in catalogs, never on a job. Wondering if they hold up better with the freeze/thaw cycles we get here.