| Author |
Message |
Melissa Aguiar, CSI, CDT, SCIP
Senior Member
Username: melissaaguiar
Post Number: 14
Registered: 12-2003
| | Posted on Thursday, May 26, 2005 - 12:06 pm: |    |
Hey all,
I need some help. I have an Archy that wants a Contractor to change the type of ballast that they are putting on an EPDM roof. They said that the ballast is not what I spec'd which was smooth, washed, riverbed rock ranging in size from 3/4" to 1-1/2". The Owner says the size range is larger than than and that the rock is not smooth, the rock is also jagged and sharp.
The sub that is putting it on says that they are bringing it in from the Ohio river and that they do not know of any other place to get ballast in Arkansas. (Work is in Nortwest Arkansas)
Please give me your suggestions on where I might find some ballast that will meet these ranges? |
Marc C Chavez
Senior Member
Username: mchavez
Post Number: 111
Registered: 07-2002
| | Posted on Thursday, May 26, 2005 - 12:48 pm: | |
Id say let him put it down BUT...
If jagged, remember to lay down roof mfr. approved geofabric to protect membrane. Run it up the at preimeter and edges at least 2-3 inches. and discontinue at scuppers and other exposed places.
Larger should be no problem.
ASTM C136 small stuff and ASTM D448 larger stuff. The wieght should be about the same at 13# per square foot (1300lbs per square)
C136-05 Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates
D448-03a Standard Classification for Sizes of Aggregate for Road and Bridge Construction
There are NO sources of river rock in the SE USA?
that's hard to believe. |
John McGrann
Senior Member
Username: jmcgrann
Post Number: 49
Registered: 03-2002
| | Posted on Thursday, May 26, 2005 - 12:55 pm: | |
As surprising as it may seem, there are regional shortages of naturally occurring stone suitable for roofing ballast. Seems a lot of the good stuff is already up on top of other roofs. |
Robert E. Woodburn
Senior Member
Username: bwoodburn
Post Number: 32
Registered: 01-2005
| | Posted on Thursday, May 26, 2005 - 01:20 pm: | |
If it's jagged and sharp, it could well puncture the membrane, and with EPDM it may be hard to locate the damage, making repairs much more difficult. Rolling a heavy load, like a replacement A/C unit, across the roof could perforate it with countless cuts - a nightmare. (I have seen EPDM roofs that were riddled with patches, and those weren't even ballasted.)
It's crushed stone that is jagged and angular. Looks like that, not river rock, is what you've got. And the runaround, to boot.
Did the spec require that it be from a nearby source? If not, it's available, somewhere. Is it available in a different size range? If so, would using a smaller size be an acceptable change in order to get smooth rounded gravel?
Or - here's a real long shot - could the term "ballast" itself be part of the problem? Is someone confusing this with railroad ballast, which preferably IS crushed stone, since for that use, the angularity is desirable? |
Tobin Oruch, CDT
Senior Member
Username: oruch
Post Number: 23
Registered: 04-2003
| | Posted on Thursday, May 26, 2005 - 01:47 pm: | |
To further reduce puncture issue, should be sure to require pads or pavers where traffic is likely -- or paver the whole thing. |
Don Harris CSI, CCS, CCCA, AIA
Senior Member
Username: don_harris
Post Number: 38
Registered: 03-2003
| | Posted on Thursday, May 26, 2005 - 02:01 pm: | |
I'm curious...What, if anything, was submitted and approved? Robert is correct jagged, sharp and EPDM do not play well together. |
Anonymous
| | Posted on Thursday, May 26, 2005 - 08:04 pm: | |
<<jagged, sharp ballast>> ... may void the mfrs warranty. |
David R. Combs, CSI, CCS, CCCA
Senior Member
Username: davidcombs
Post Number: 60
Registered: 08-2004
| | Posted on Friday, May 27, 2005 - 12:25 pm: | |
Just as a side, be careful about specifying ballasted roofs in high wind-speed areas. Under the right circumstances, the ballast can become flying debris, raining down on everyone below (and into the building's windows). |
William C. Pegues, FCSI, CCS
Senior Member
Username: wpegues
Post Number: 399
Registered: 10-2002
| | Posted on Saturday, May 28, 2005 - 04:19 pm: | |
David has a good point here, and insulation manufacturer's for ballasted roofs basically address this, Dow has a good publication that talks about your wind speed area, height of the membrane above the ground and height of the parapet above the membrane.
I am not sure that the roof membrane people have as good a recommendation, and there are factors that are not required for the membrane that hoding down insulation can require.
But, they do address blow off requirements by having the ballast become larger and larger minimum size. And at some point when the conditions become worse (higher wind, lower parapet, higher off the ground) you can wind up with pavers at all outside perimeters, all inside perimeters (people often forget that) and at all penetrations (roof drains and the like). And then as it worsens, you get more and more rows of these, up to 4 rows, extending 10 feet, and sometimes strapped to each other.
i have a pdf file that is this document from Dow - its on my office system which I can send out on Tuesday if anyone is interested.
Again, it is addressing ballast for insulation, not for direct to membrane - but some issues like the size of the ballast will be common, and it makes good reading for general principals anyway.
I give copies of this to my project managers and project architects, so that our drawings express these requirements.
Wiliam |
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