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I have a cedar roof that needs replacement, and I would like to replace it with metal. One area of the home has vaulted ceilings with continuous soffet vents. There is not enough overhang on the gables to install venting up the sides of the home. The top of this area ends at a short wall for the upper floor of the house. Adding any type of continuous ridge venting is not possible due to high requirements. (The height of the cedar barely fits under the upper roof's internal gutter system.) My cedar roof never had condensation problems, should I be concerned with installing a metal roof without adding additional venting?
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First it would help if I knew the region you live, how old the cedar roof was when it failed and what class od cedar it was. This would give an indication as to whether you have a condensation problem or not.
A properly installed cedar roof is installed on spaced sheathing which allows the wood to breathe which is critical to its longevity. Obviously if you are in a dry climate such as phoenix it is less of an issue.
I am a strong advocate of good ventilation regardless of roof material. At the turn of the last century, they relied on the ceiling, attic and roof to exhaust the moist air out and designed accordingly.
Changes in home usage has increased significantly the amount of moisture and insulation upgrades have changed the assembly causing problems at times. Who knows what our homes will be required to in the next 50 years.
You may already have an air space under the shingles and if it is on spaced sheathing, it is venting through the wood shingles. Cedar will absorb and exhaust condensation quite well and if it breathes will last a long time. Changing the roof material is a change regardless.
You will pick up some room, when the old shingles are removed. Depending on the new system you may have roof to vent as it only requires 1" with vented mesh between the roof materioal and the wall flashing. Hopefully it is in good shape and you can tuck under itand provide ventilation with the mesh.
At vertical wall intesection, the same detail can be used as well. If you have more info contact me directly and I can help more. good luck.
10/9/2003
Dura-Loc Roofing Systems, Inc.
10/9/2003