Calculating support box cut out from center on sloped ceiling

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metelskiy

New Member
Nov 18, 2021
15
Beaverton, OR
This may sound like a stupid and simple question but I need help. Basically I need to install support box in 6/12 pitch ceiling. I used plumb bob to determine center of the support box. Now That the ceiling is sloped, it’s obviously not going to be same distance from center to sides. How to precisely calculate the cutout ?
 
This may sound like a stupid and simple question but I need help. Basically I need to install support box in 6/12 pitch ceiling. I used plumb bob to determine center of the support box. Now That the ceiling is sloped, it’s obviously not going to be same distance from center to sides. How to precisely calculate the cutout ?
Measure the angle draw it on the side of the support box then measure that.
 
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You can hold it against ceiling, level, as it will go thru the ceiling. Use a straight edge on what will be the long side, to the ceiling, and mark the spot. You will be able to draw the rectangular cutout on the ceiling. Just remember this box needs to fit between the ceiling rafters that should be 16" on center. To get my straight chimney where it was centered in the corner, I needed cut a rafter and build a box with a double header.