> PVC boards under terne roof Harvey Lankford 1 Posts 1937 house, painted raised seam terne porch roof in good condition. Problem is original inadequate flashing design and leak. I removed part of porch ceiling to access underside, propped up rotted joist and rafter end, removed about 10 square ft rotted sheathing 1X8s.Underside of terne is still good, red coating seen. Will fix leak. Will replace structural wood with bolted-in treated lumber. ![]() DetailsBuildDirect – Comfort Plus Deck Veneer – Walnut - Profile View. ![]() New treated 1X8s not recommended as being too corrosive touching the metal roof. Should I use plain wood 1X8s? No problem if awkward leak site is fixed well, but if it recurs, using PCV 1X8 board is expensive but would avoid future rot. Are they too hard and expand/contract rub against the terne? By not breathing would they trap water. Any other risk? Thanks for any thoughts. Mere naseeb mein remix mp3 download. Attachments: Posted On: 12/05/10 8:38AM| Geographical Location: Richmond VA Info @windowsonwashington.net 773 Posts 'An informed customer is our best customer.' Plastic/composite lumber will probably expand and contract a bit more than acceptable ranges for structural lumber. You could use PT and just put an acceptable vinyl flashing between the metal and the beam or go with the untreated and hope you fix the moisture problem. Given the vertical orientation of the beams, it is unlikely they will rot as they will want to shed their moisture. Replied On: 12/06/10 9:29AM Nate Libbey 213 Posts Plain wood will work fine. You can also use 'Blue-Wood' borate treated 1x4s as they don't have a chemical reation with the zinc coating. Just make sure you don't use copper oxide treated wood. Replied On: 12/06/10 9:30AM all Thanks unfortunately the specs on Blu wood say that while it is no more corrosive than CCA, this means that it IS still corrosive (but not as much as newer PT), therefore it is not approved for use in contact with metal roofing such as terne (per Follansbee) The vertical vs horizontal orientation did not help before toa void rot- all types of exposures (rafter end, joist end, roofing planks) were all rotted by the original problem The use of plain modern wide-grain wimpy lumber bothers me for this repair. The former, denser, harder, resin-loaded 1X8s of 1937 are not available so easily. ![]() So to avoid the corrosion problem of PT, to avoid the rotting risk of plain wood (if/when the leak repair fails), I thought of using the PVC. All the choices will outlive me, but I still want to do it right. I imagine there is little experience with what I am proposing to do. Replied On: 12/06/10 2:57PM all Maybe I read the specs wrong on blu wood. Can't find where I read it was similiar to CCA in corrosion.
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