TOPIC: Is A Metal Roof Right For My House
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Hi, thanks for advance for comments. i have a trailer in a northern climate with snow. looking at replacing the existing metal roof and take a few steps to prevent the ice damming and leakage that has occured in the past. the roof is 3:12 and will be stripped to the plywood sheathing. The plan is for the roof plywood to be covered with underlayment, then rigid insulation, then strapped with 2X4 parallel to the eaves, then fascia flashing then ice/water shield along the eaves over the flashing and finally finished with new metal roofing (with lap sealant). The insulation in the ceiling will also be improved, but it is a mobile home with no truss heel height at the eaves so insulating that area properly is tough. Also no soffit venting is present, however there is gable and roof venting. Questions:
3:12 is fine for metal assuming you are using a system that is rated for that pitch.
I would incorporate at least a couple of inches (3" is better) of foam into the equation on the roof side. I would strip the roof, install the foam, stagger the seams, install a wood buck/box around the perimeter for easy attachment points for the roof.
Then install your ice/water and underlayment over the foam.
I like the idea of a set of vertical battens with some horizontal strapping so as to create a vent space above the roof that will keep the roof much closer to ambient temperature.
thanks for that. do you see any issues with the insulation over the roof deck and the insulation in the ceiling and the subsequent air cavity in the truss between the two (vented). I wonder about this area accumulating moisture?
The more insulation on the top, the warmer the framing is going to be.
The reality is that air permeable insulation is never a really good plan in a vaulted ceiling to be honest. I would like to see more insulation to the exterior and then you can get away with just a full fill of OC SPF or the CC SPF and batt fill at that point.
Never a bad idea to incorporate something like Mem-Brain on the interior surface for moisture control.
If the ceiling is going to be dry walled, the biggest thing it to make sure the drywall is airtight.
Look up ADA - Airtight Drywall Approach.
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