Home Repair forum - Flat roof materials

Author

Flat roof materials

upand_at_them@yahoo.com

2008-02-19, 1:25 pm

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

Joe

2008-02-19, 5:25 pm

On Feb 19, 11:13=A0am, upand_at_t...@yahoo.com wrote:
> 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? =A0When I bought
> the house the inspector said something about foamboard? =A0I 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

Your idea sounds OK, but check the manufacturers directions to see if
foamboard is required as an underlayment and not a slope building
material. Good luck.

Joe.

mkerna@gmail.com

2008-02-19, 5:25 pm

Well, the manufacturer says that it "will adhere to wood, metal,
plastic, glass, fiberglass, rubber, masonry, brick, smooth surface
built up
roofs, non-granular roll roofing, non-granular "half lap" roofing,
painted
surfaces, wood fiberboard, lightweight concrete, and
polyisocyanurate."

Besides wedging the underlayment, would there be any other way to
slope it?

Mike

Joe

2008-02-20, 1:26 pm

On Feb 19, 2:43=A0pm, mke...@gmail.com wrote:
> Well, the manufacturer says that it "will adhere to wood, metal,
> plastic, glass, fiberglass, rubber, masonry, brick, smooth surface
> built up
> roofs, non-granular roll roofing, non-granular "half lap" roofing,
> painted
> surfaces, wood fiberboard, lightweight concrete, and
> polyisocyanurate."
>
> Besides wedging the underlayment, would there be any other way to
> slope it?

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

Robert Allison

2008-02-20, 5:25 pm

upand_at_them@yahoo.com wrote:
> 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

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.
Georgetown, TX

marson

2008-02-20, 5:25 pm

On Feb 20, 1:56 pm, Robert Allison <rimsho...@verizon.net> wrote:
> upand_at_t...@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.
> Georgetown, TX

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

LinkBot