Flat roof materials

I've looked in to this and it looks straightforward enough that me and a friend could replace my rubber roof with new EPDM.
My question is that I know it has a slight pitch to direct rain water towards the drain, but what was used to shape the roof? When I bought the house the inspector said something about foamboard? I was thinking of using wedges to nail to the top of the joists that the underlayment will lay on...It would be easy enough to create the slight pitch that way.
Mike
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On Feb 19, 2:43 pm, snipped-for-privacy@gmail.com wrote:

Foam board comes in thicknesses from 1/4" to 2", maybe more, so it should be possible to lay a decent slope for what you need by transitioning from one thickness to another. A right angle grinder would take care of any transition junctions that are too abrupt. HTH
Joe
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upand_at snipped-for-privacy@yahoo.com wrote:

GAF and many other companies make foam board insulation and wedge shaped foamboard to provide slope. We use it all the time on commercial buildings to form the slope. Either that, or the roof is framed using standard roof joist systems which are then built up with wedge cut members to slope the roof, which is then decked. The foam board can then be used for insulation and the roofing material goes over that.
Here is an example of sloped foamboard:
http://www.gaf.com/Content/Documents/1040.pdf
--
Robert Allison
Rimshot, Inc.
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Robert is right as usual. Note that usually you have to screw down coverboard over the foam (otherwise the contact cement will melt the foam). coverboard is just 1/2" fiberboard held down with washers. You could do it with wedges as you suggest, but then you would have to sheath it with 3/4" t and g plywood--at least that is what is specced on the flat roofs I do. Might find information here: http://www.watertighttech.com/home.shtm
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