mgbinspect Posted August 18, 2010 Report Share Posted August 18, 2010 Greetings brethren, Workin' on a very large bay front property inspection. Click to Enlarge 69.07 KB I've seen this roof setup a number of times before, and I've always been fine with it. But, I thought it might be prudent to poll the TIJ brain-trust to see if anyone has had bad experiences or is aware of any problems with this marriage. It's CMU patio stones over a membrane roof. I've always thought it was fine. Some of the stones rock a bit, which causes me to wonder if they can't cause some materials chaffing. Any thoughts or concerns? Click to Enlarge 58.65 KB Click to Enlarge 28.82 KB Thanks in advance for all insights. Mike Quote Link to comment Share on other sites More sharing options...
kurt Posted August 18, 2010 Report Share Posted August 18, 2010 What membrane? Mod bit, granulated, what? Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 What membrane? Mod bit, granulated, what? Definitely not selvedge (aggregate), Kurt. I could only see about 2" around the perimeter, but it appears to be what I've always thought of as a modified rubber membrane - the look/finish/feel of an automobile inner tube - heavier of course. Built in 2006. Quote Link to comment Share on other sites More sharing options...
Marc Posted August 18, 2010 Report Share Posted August 18, 2010 I don't see an issue with it, as long as there is no conditioned space beneath it. Marc Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 I don't see an issue with it, as long as there is no conditioned space beneath it. Marc It' the master bedroom balcony that is also the roof over the monstrous eat-in kitchen. As I said, in general, I'm fine with it. I mostly want to hear of any precautions or bad experiences with the setup. Quote Link to comment Share on other sites More sharing options...
kurt Posted August 18, 2010 Report Share Posted August 18, 2010 There's no such thing as modified rubber membrane. Is it EPDM? That looks like inner tube material, sort of. EPDM can be ballasted, but I'm not sure about concrete pavers. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 There's no such thing as modified rubber membrane. Is it EPDM? That looks like inner tube material, sort of. EPDM can be ballasted, but I'm not sure about concrete pavers. I think you're probably right - looking at photos of EPDM, that looks to be the animal. It has the look and feel of a rubber compound - thick material, of course with an apparent mesh reinforcement in it that slightly telegraphs through the material surface. Quote Link to comment Share on other sites More sharing options...
Marc Posted August 18, 2010 Report Share Posted August 18, 2010 The following is from the Building Envelope Design Guide produced by the National Institute of Building Sciences (NIBS) available here. If crushed aggregate is specified, a stone-protection mat between the membrane and aggregate should be specified to avoid puncturing the membrane. A stone-protection mat is also recommended when smooth aggregate is used because some sharp fragments are often among the smooth aggregates. Also, aggregates sometimes fracture into very sharp pieces after they have been installed. It is also a conservative practice to specify a mat to protect against abrasion and puncture from fragments during paver installation. A somewhat thinner mat is normally sufficient for paver-ballasted jobs. Marc Quote Link to comment Share on other sites More sharing options...
Bill Kibbel Posted August 18, 2010 Report Share Posted August 18, 2010 EPDM is synthetic rubber. The top manufacturers (Firestone, Carlisle, etc.) require a protective barrier called paver mat, between concrete pavers and the roofing membrane. Carlisle has a rubber paver that doesn't need a mat. You should be able to easily find if the mat is present. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 The following is from the Building Envelope Design Guide produced by the National Institute of Building Sciences (NIBS) available here. If crushed aggregate is specified, a stone-protection mat between the membrane and aggregate should be specified to avoid puncturing the membrane. A stone-protection mat is also recommended when smooth aggregate is used because some sharp fragments are often among the smooth aggregates. Also, aggregates sometimes fracture into very sharp pieces after they have been installed. It is also a conservative practice to specify a mat to protect against abrasion and puncture from fragments during paver installation. A somewhat thinner mat is normally sufficient for paver-ballasted jobs. Marc That was useful. I don't think there's any type of protective mat under the CMUs, which are about 12 x 12 x probably 2" Kurt (or anyone else), any thoughts? I'll probably call for a roofer to bless the installation. I'm sure it's fine for now - no leaking and the material I can see looks great - like new. But the way some of the pavers rock suggest that maybe the roof sheathing should have been thicker or doubled. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 EPDM is synthetic rubber. The top manufacturers (Firestone, Carlisle, etc.) require a protective barrier called paver mat, between concrete pavers and the roofing membrane. Carlisle has a rubber paver that doesn't need a mat. You should be able to easily find if the mat is present. Thanks Bill, I believe the second photo shows the turned up edge of that mat. I think we're good to go then, except I still don't like the way units rock over the joists. I bet they should have doubled up the sheathing. Quote Link to comment Share on other sites More sharing options...
John Kogel Posted August 18, 2010 Report Share Posted August 18, 2010 Another concern is keeping the drain(s) clear. The drain has to be in the membrane below the level of the pavers, so it should be easily accessible. I've seen them covered so you have to lift pavers to find them, wrong. Quote Link to comment Share on other sites More sharing options...
mgbinspect Posted August 18, 2010 Author Report Share Posted August 18, 2010 Another concern is keeping the drain(s) clear. The drain has to be in the membrane below the level of the pavers, so it should be easily accessible. I've seen them covered so you have to lift pavers to find them, wrong. John, No indication of a drain other than a slight slope. the balcony is probably about ten feet wide and fifteen feet long. I see no scupper or indication of an internal downspout system. Quote Link to comment Share on other sites More sharing options...
kurt Posted August 18, 2010 Report Share Posted August 18, 2010 Put down small grain ballast over the paver mat, bed the pavers into the stone. That way, they don't rock or move. Quote Link to comment Share on other sites More sharing options...
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