A lot of places require a secondary membrane under shingles although,
up north I have seen them nail the shingles right to the plywood.
I used Grace Ice and Water under mine but we have hurricanes that will
peel shingles off, even with the required 6 nails each.
On Sep 7, 4:49 pm, email@example.com wrote:
I never understood why someone would omit the building paper when
doing so instantly voids the warranty. I guess some don't think the
warranty is worth anything at all, but if you never use it what's it
really worth? When someone works for someone else they can't be
taking liberties with warranty coverage and the owner's piece of
mind. Finding out they'd cut a corner, and a cheap one at that, and
potentially put the owner at greater financial risk, won't reflect too
well on them.
The building felt requirement doesn't make a whole lot of sense to
me. I'm with you on the membrane underlayment and would understand
if it were required everywhere. The only problem I'm seeing with it
is that some guys put on the membrane and then feel no particular rush
to get the shingles on. The manufacturers all stipulate the maximum
length of exposure to sunlight as it degrades the membrane. One house
going up near here has been under the membrane for almost nine
months. I guess even if the membrane suffered some degradation it
would still be at least equal to building felt...
On Tue, 07 Sep 2010 14:58:07 -0700, RicodJour wrote:
Yeah, if it's needed for warranty, I'd do it. If it's not, then it'd
probably depend on the building's use and the underlying roof
construction (separate timbers vs. OSB, say). I'm not sure that felt does
much for stopping moisture, but I suspect it helps to make things air-
tight (so may be beneficial on any kind of heated structure)
No building code where I am - but also not much building going on, so I
can't comment on what standard practice is!
If you're talking about reroofing, mebbe so, but code requires felt.
I'm in NY, so this is the NY state code, which is a slightly modified
§RR905 REQUIREMENTS FOR ROOF COVERINGS
§RR905.1 Roof covering application. Roof coverings shall be applied in
accordance with the applicable provisions of this section and the
manufacturer's installation instructions.
The manufacturers all require it, so code requires it, but there's
also this specific bit:
§RR905.2.7 Underlayment application. For roof slopes from two units
vertical in 12 units horizontal (17-percent slope), up to four units
vertical in 12 units horizontal (33-percent slope), underlayment
two layers applied in the following manner. Apply a 19-inch (483
strip of underlayment felt parallel with and starting at the eaves,
fastened sufficiently to hold in place. Starting at the eave, apply
inch-wide (914 mm) sheets of underlayment, overlapping successive
19 inches (483 mm), and fastened sufficiently to hold in place. For
slopes of four units vertical in 12 units horizontal (33-percent
or greater, underlayment shall be one layer applied in the following
manner. Underlayment shall be applied shingle fashion, parallel to
starting from the eave and lapped 2 inches (51 mm), fastened
to hold in place. End laps shall be offset by 6 feet (1829 mm).
Where are you and what code do they use in your area that permits
omission of the underlayment?
Sorry, I should have been more explicit. I'm in Ontario, Canada, right
across the lake from NY State.
Shingles right on top of plywood is quite legal here, and is 100% what new-
home builders do. Not a single new-home builder here puts anything more
than bare shingles, even on a million-dollar home, unless the buyer
specifically purchases upgrades. Believe it or not.
So, who said builders always follow Code? :)
I'd be really surprised if that is not a violation of Code in Canuckstan
being as in general Codes mimic others very closely and the reqm't for
following manufacturers' instructions is quite the common first step.
I looked up the Ontario code online, and maybe it was the format, but
I found it confusing and ambiguous. It clearly calls for eave
protection underlayment, but the wording for the rest of the roof is
unclear. Since both the Ontario and NY codes are based on the IRC,
they should have a lot of similarity. Not sure why there's such an
omission for the underlayment.
The most definitive thing I found pertaining to underlayment was here:
Ontario practice is about a fifth of the way down the page. So it
seems that Ontario feels there is less of a need for underlayment than
even nearby parts of Canada. Maybe you're in a micro-climate
No one is arguing your personal experience. I'm just trying to figure
out how, out of every area that has adopted the IRC which requires
underlayment, Ontario is okay with omitting it and makes no reference
to the manufacturers' instructions requiring it. It's odd, and from
the other responses you can see that I am not the only one that finds
It appears the Code references the Canadian version of the ASME
Standards for asphalt shingles based on a summary of the Code
requirements I found which on installation says--
"* Shingles shall be applied according to methods outlined by the
National Standards of Canada. Roof slopes 1:3 and steeper shall conform
to CAN3-A123-M85. Roof slopes 1:6 to less than 1:3 shall conform to
So, looking for the applicable Standards, best I came upon was the
following to catalog pages from the sales site--
CAN3 A123.51-M85 (R2006)
Asphalt Shingle Application on Roof Slopes 1:3 and Steeper
Canada National Standard/Canadian Standards / 01-Dec-1999 / 23 pages
This Standard describes the minimum application requirements for asphalt
strip shingles or low slope shingles on roofs with slopes from 1:3...
CAN3 A123.52-M85 (R2006)
Asphalt Shingle Application on Roof Slopes 1:6 to Less Than 1:3
Canada National Standard/Canadian Standards / 01-Dec-1999 / 24 pages
This Standard describes the minimum application requirements for asphalt
strip shingles or low slope shingles on roofs with slopes from 1:6 to
less than 1:3...
Unfortunately, they're published Standards and not generally available
online which is what makes finding the info so tough.
I'd be willing to bet both either include the requirement or rely on
following manufacturers' installation procedure for the particular
product. Universally afaik, the manufacturers' recommend same.
I'm still betting Code says "do it" even if it is widely ignored and
(apparently) not enforced.
That is changing real fast here in Waterloo Region. The Toronto
builders building here are still pulling that shit - but the better
local builders are ALL going to felt underlay as a minimum, and on the
expensive houses full membrane. (and many expensive houses are no
longer getting regular shingle roofs any more either)
Mind you, a "million dollar home" isn't what it used to be any
Boggle. Not even ice membrane on the overhangs and in the valleys? (Both
required by code around here, new or re-roof.)
I'd never omit it, or knowingly buy a house without it. Seen shingles
torn off in windstorms too many times.
On Tue, 7 Sep 2010 17:52:31 -0700 (PDT), RicodJour
A lot of roofers have been compeating strictly on price and not
installing any roof felt for several years. Some have been using roof
felt for ice-dam prevention.
The smart ones have finally figured out price isn't everything, and
there will always be someone able to do a worse job for less - so are
using roof felt again, as well as REAL ice guard. Some of the premium
roofers are using BluSeal ice guard membrane over the whole roof now -
and doing the job for not a whole lot more than the cheapskates.
The builders here in the South (Alabama) seem to all use felt under
the shingles. My house in NY didn't have any felt under the
shingles. I don't remember if my VT house had felt or not. I think
One other purpose of felt, it makes tearing off the roof much easier,
though builders wouldn't care much about that.
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