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TOPIC: Condensation Issues

No vapor barrier

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As part of a the purchase of a house in far south Texas insurance required a new roof to be put on at the seller's expense. We have the right to inspect/reject the work as it is done. They are putting on 28 gauge painted steel over 20 year old composition (decent) shingles as follows: no tear down and rebuild, no extra felt backing, simply putting up 1X6 untreated lathing strips and attaching the roofing. Most of the house has vaulted ceilings with 6 inch insulation, but there is an attic with an HVAC unit that is uninsulated with no vapor barrier between the rafters. Won't this space create condensation and leaking over untreated lathing, then pooling which will rot? Also, if the ridge vents leak in a hurricane won't the same thing happen? Thanks for advice...there's no code in the country but I can still change the roof.
Guest User

9/8/2004
You really need to check with the product manufacturer and get their recommendations and ask to see their product approval report on installation over existing roofs. While there is no code in your area a proper roof system needs a good underlayment. If the existing asphalt shingle roof is in good condition it can substitute however products are generally required to be rain tested this way. It also needs ventilation.For the vaulted cxeilings in needs 1" min and more is better of free air space that is vented at the eaves and ridge. There are venting ridge products tested to resist the wind driven rain from hurricanes. I am unsure of what you mean in the attic as to a vapour barrier. If the HVAC unit is in an unheated attic, then make sure any exposed pipes are insulated and that the attic has ample ventilation which is to be supplied equally at the ceiling level and ridge. While you are at it choose a lighter colour or ones that are enegy star approved (Check out our web site at www.duralocc.com) and that the paint is either a PVDF or SMP both with ceramic pigments so that you get good service life. Also the substrate should be minimum G90 or AZ50. Hope this helps.
Allan Reid
Dura-Loc Roofing Systems, Inc.

9/8/2004
Thanks for the response. They are intending to put the batting 24 inches apart, untreated, but claim this will be real strong. Also, the ridge cap is now cut 1.5 inches wide for venting and a long one piece black poly substance is to be used for the ridge as a rain guard and to breathe. I am a little concerned that the eaves aren't vented where the ceiling is vaulted but the ridge cap is...is this a negative, or just a neutral condition. The shingles undeneath were in good enough shape to be rain tested. Another issue is that 28 guage seems standard around here but seems a little light(?). Once again, thanks for your expertise and time.
Guest User

9/13/2004
Passive ventilation requires intake and exhaust and they should be balanced. depending on the profile of vertical rib that you will use, it will intake through the flutes so the size and quzntity of flutes will be the governing factor. They do make vented closure strip for the flutes as well. The strength of the sheets is dictated by profile, then steel strength and then thickness. Check with the manufacturer.
Allan Reid
Dura-Loc Roofing Systems, Inc.

9/13/2004
Thank-you, your help has been excellent!
Guest User

9/15/2004