Most
manufacturers recommend both tarpaper (often called building felt) and rosin
paper. The tarpaper provides a
secondary water barrier in the event of a failure of the primary (metal) roof. In almost all cases rosin paper is
required between the metal and substrate to allow the metal to slip when it
expands and contracts. I suggest
you check with the supplier and/or installer to get their recommendation. It could affect the warrantee.
Venting is
not usually needed between the metal and substrate but ventilating attics and
other cavities above the ceiling is usually required to remove moisture vapor
buildup and secondarily to reduce temperatures. Most shingle roof warrantees will not be valid without
venting. There is a faction that
recommends venting in most cases but I do not subscribe to that theory.
Cheers,
Ralph
Bicknese
-----Original
Message-----
From: The Gros family
[mailto:pakamama@cswnet.com]
Sent: Thursday, January 03, 2002
7:52 AM
To: Environmental Building News
Subject: [GBlist] tar-paper for
roofing
building
a metal roof on top of OSB sheets (actually using "solarboard"
which has an aluminum-foil backing for radiant-heat blocking). we'll have
an un-insulated, well-ventilated (open-ridge) attic underneath.
question:
is it useful at all to put a layer of tar paper between metal and wood (to
limit condensation on wood surface ?? or??). if yes, is there a need for a
(ventilation) space above tar paper?)
thanks
