We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

Thanks,
George

"George" wrote in message
...
We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

Thanks,
George

4:12 is the minimum for a "standard installation". The IBC code allows
shingles down to a pitch of 2:12 with restrictions.

At 3:12 I would use 30 pound felt well over lapped and reduce the exposure.
The roof may not last quite as long but it should shed water. It may also
affect your warranty. Never seen one of those pay off any way.

Check for local code restrictions before you start. Some local codes are
more restrictive.


Colbyt

On Aug 13, 3:03*pm, George wrote:

snip

if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

That would likely work, but using Permafelt instead of 30 lb. felt
would be more effective, and somewhat pricier, but cheaper than EPDM
or other membranes. HTH

Joe

George wrote:
We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?


In conjunction w/ Colbyt's suggestion, look at the manufacturer's web
site for information. IIRC, most have instructions for minimum slope
installations and also minimums. I was thinking 4:12 was a little
steeper than what I recalled them stating, but I could be wrong (and
didn't go look).

--

On Wed, 13 Aug 2008 16:03:38 -0400, George
wrote:

We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

Wish I could help. Come on, let us know why a shallow roof would
solve yoiur problem?

On Wed, 13 Aug 2008 21:31:47 -0400, mm wrote:

On Wed, 13 Aug 2008 16:03:38 -0400, George
wrote:

We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

Wish I could help. Come on, let us know why a shallow roof would
solve yoiur problem?

Hard to describe. It's an (old) L-shaped addition on the north side of
the house. The parallel section (ie, along the house) has a block
wall. The perpendicular section is wood frame, is wider than the
parallel section, and its edge is lower ... as it needs to be, to keep
the 4:12 pitch.

So, at the valley where the roofs meet, instead of neatly coming
together at the corner, the one roof ends some distance up from the edge
of the other. And, the second roof plane extends under that first one,
creating a very shallow cavity. That cavity seems be a source of decay,
AND an irresistable magnet for birds and squirrels.

If I raise the wall on the perpendicular section, the two roofs will
meet at the corner, and the cavity is gone. Only raising the wall
lowers the pitch.

HTH,
G

On Wed, 13 Aug 2008 23:17:41 -0400, George
wrote:

On Wed, 13 Aug 2008 21:31:47 -0400, mm wrote:

On Wed, 13 Aug 2008 16:03:38 -0400, George
wrote:

We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

Wish I could help. Come on, let us know why a shallow roof would
solve yoiur problem?

Hard to describe. It's an (old) L-shaped addition on the north side of
the house. The parallel section (ie, along the house) has a block
wall. The perpendicular section is wood frame, is wider than the
parallel section, and its edge is lower ... as it needs to be, to keep
the 4:12 pitch.

So, at the valley where the roofs meet, instead of neatly coming
together at the corner, the one roof ends some distance up from the edge
of the other. And, the second roof plane extends under that first one,
creating a very shallow cavity. That cavity seems be a source of decay,
AND an irresistable magnet for birds and squirrels.

If I raise the wall on the perpendicular section, the two roofs will
meet at the corner, and the cavity is gone. Only raising the wall
lowers the pitch.

This should be a question on a solid geometry test. Who says that
high school math was worthless?

HTH,
G

"mm" wrote in message
...
On Wed, 13 Aug 2008 16:03:38 -0400, George
wrote:

We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

Wish I could help. Come on, let us know why a shallow roof would
solve yoiur problem?

Why not just ask the shingle manufacturer what the minimum acceptable pitch
is for their product to be watertight? Might even be on their website.....

on 8/13/2008 4:03 PM George said the following:
We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. But, that's also
what it was in the Stone Age.

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

Thanks,
George

A Google search on 'asphalt shingles minimum roof pitch' brings up a
number of sites that say 2:12.

--

Bill
In Hamptonburgh, NY
in the original Orange County
To email, remove the double zeroes after @

On Aug 13, 4:03*pm, George wrote:
We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. *I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. *But, that's also
what it was in the Stone Age. *

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

Thanks,
George

ya gotta use more shingles with less exposure when cheating, you might
only show 3" exposure to pull it off

On Aug 13, 1:03*pm, George wrote:
We have a roof problem that could most easily be solved by doing
somethign that would lower the pitch from 4:12 to 3:12. *I keep hearing
that 4:12 is the "minimum" pitch for a shingled roof. *But, that's also
what it was in the Stone Age. *

I wonder if that rule still applies, if I underlaid the whole thing with
a bituminous membrane (aka "ice and water shield")?

Thanks,
George

Been awhile but IIANM just visit your local supplier and look at a
shingle bundle. I recall that information (along with almost every
other answer to roofing questions) is printed right on the wrapper.

Harry K