recommended installation proceedure

Wayne Weick
9/27/2005
I'm intersted in installing a metal roof over old 3 tab asphalt shingles. Do I need to do anything other than strip over the old shingles with 1x4's and then fasten the steel roofing to the 1x4's. Next, if the old shingles and tar paper have been removed by mother nature. Should I apply tar paper (felt) to the old roof then 1x4's followed by the steel or should the felt be installed between the steel roofing and the 1x4 lathes rather than under the 1x4's.
Allan Reid
Dura-Loc Roofing Systems, Inc.
9/28/2005
It sounds like you are installing a vertical rib metal roof. There are certian requirements in the building codes that should be met especially in a wind zone. Choose a product and ask to see the product approval report that will indicate it has been tested and how can be installed and how to fasten it for the various wind zones. Certainly, I would recommend tearing off the existing roof down to the deck, renail the decking to the new code standards, install a proper inderlayment and then the roofing. The code also calls for ventilation which will need to be addressed.
Wayne Weick
9/28/2005
I plan on using "X-press panel" with 'ceram-a-star 950' finish. My primarly question is rather the metal should be fastened directly to the 1x4 strips or should 'tar/felt' paper be installed between the metal and 1x4 strips?
Allan Reid
Dura-Loc Roofing Systems, Inc.
9/29/2005
I am not familiar with the panel but that is a good paint system. Again contact tyhe manufacturere and get their recommendations. The code allows for the underlayment to be in either location. When using a felt paper it is not capable of spanning the strapping so it needs to be on the deck. The down side is that on vertical rib sheets, any condensation could run down the underside and get trapped at the strapping if you are in a climate that has many dew point crossings and high humidity. If the space is not vented properly, continuous wet lumber will eventually release the acids in the wood which could react with the metal backing and start corrosion. Ufortunately I do not have ennough info to give you the best answer. There are some ungraded undelayments that will span over the strapping that do not tear such as Triflex 30 that would resolve all the above. Hope this helps.
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