Sod roof

[David Meiland]

I looked at a house for a potential buyer recently, to price out some work on the exterior that will need done if they buy it. The house has a sod roof, or living roof, or green roof, or whatever you want to call it... it's got lots of dirt over a membrane and vegetation growing on it. I didn't look closely at it but do have a photo if anyone wants one. They had a licensed HI perform an inspection, but apparently a question has come up about how to inspect such a roof, and who could do it. The buyer's agent called to ask my opinion.

Given that the membrane is almost entirely concealed, what makes sense in a situation like this? I can do an IR inspection from the interior, and presumably the HI checked the underside with his moisture meter. What else?

[John Kogel]

I think they should get info from the builder.

I would want to know what the membrane consists of, and what the sheathing is under it. The depth of the soil would be good to know. I suppose you could jab a probe in to measure it.

I would expect to see some very solid supports under that roof, because the weight factor is significant.

Check the drainage. The water has to seep out of there somehow. Good luck with it.

[kurt]

I've seen a few of these, and there's no way to inspect them. You have to get installation details from the builder. Even then, there's no way to check to know if the details are installed correctly.

They're not complicated, but they're very involved. The one's that work are mightily expensive. There has to be structural accommodation of the (major) increased load. I had a bunch of specifications for them around here somewhere, but since I only used them a couple times, I may have tossed them.

Personally, I think green roofs are nuts. I get the environmental benefits, but it's so far outside of the average roof budget that it gets a bit silly.....very few will ever be installed, so does it really matter if .0000001% of the world has a green roof?

[David Meiland]

I haven't checked the county record, but I bet this place was built under an owner/builder permit. The owner may have details on it, he still lives there. Seems like only a matter of time before the membrane develops a leak, at which point you're up there shoveling all the dirt down into the driveway.

[kurt]

The good ones have redundant layers of membrane, drainage mat, etc.

I'd be mightily suspicious of a homeowner job.