Underlayment- flat or purlins?

Guest User
10/22/2002
Is it better to fasten metal to plywood or to shim out for ventilation? I was going to install roof on covered (30# felt)plywood and put inside and outside closures in. Will this cause condensation between the metal and plywood? What's the RIGHT way? Thanks.
Allan Reid
Dura-Loc Roofing Systems, Inc.
10/23/2002
If you live in a climate that is warmer than 50 degrees you should not be as concerned. Next is you have not described the roof assembly, building use and type of product. If you have a properly vented attic space you should feel fine installing it either way. The roof will get hot and eventually cook out the oils in the underlayment so use a better quality underlay especially if you are going directly over. Remember that you are installing a long term roof. The strapping is a great way to stand the roof off from the deck and reduce heat transfer. Also it gives yo a more positive location for fasteners especially in a re r0of situation. As t the closures, I would suggest the little extra money and use the vented closure strips available which will further help keep your roof cool and save you money. Good Luck.
Guest User
10/23/2002
I recently help put a metal roof on an addition to my mephew's house and I noticed that the excisting roof didn't have a moisture between the OSB board and the roof, shouldn't it have? I am in East Tennessee.
Todd Miller
Isaiah Industries, Inc.
10/23/2002
To the best of my knowledge, in an installation over solid decking such as OSB or plywood, all metal roofing manufacturers would suggest some sort of underlayment to protect the decking from condensation when weather phenomena occur such that condensation does form on the back side of the metal panels.
Guest User
2/19/2003
Greetings All, Would metal roofing be a consideration for use as a replacement on a flat town house type roof ? What is the minimum pitch required for the use of metal roofing materials ? This project will be a complete tear off of a 36x17 flat roof so the instalation can be done in any form needed to comply with the metal roofing material standards. If it can be used at all on a flat roof situation. Thanks in advance for any and all information in regards to this matter! M Kingsborough Sr.
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