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Old 07-09-2007, 01:24 PM   #1
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45 degree calculation

I'm not sure if this should be posted in this forum, or in a different category. Can anyone tell me how to estimate the overage when siding a wall @ 45 degrees? I'm using shiplap planking to finish the walls of my basement. Instead of running the planks horizontally, I'm running them at a 45 degree angle of a few of the walls. I've calculated out the cost of the materials if I ran all boards horizontally around the room. But I know there's a formula out there that will tell me how much extra to factor in if I'm running them at 45 degrees. I "thought" it was something like add an additional 10%, but I'm not sure. Does anyone know ? Thanks !


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Old 07-09-2007, 06:49 PM   #2
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There may be a "magic number" out there that some pro knows, otherwise,

On the two triangle cuts of each board, your scrap will be a square equal to width*width dimension.

i.e. if you had 4" boards, you'd lose 16sq-in, divide by 144 = .11 sqft loss per board

You could then figure out how many boards by drawing a 45-degree diagonal line on the wall, measuring it, then divide by board width to get a # of boards. Unless its a square wall, you'll have to draw two lines. Tough to explain...

It all depends on what size boards, the wider, the more loss in material.
the real question is... can you return any extra material?


Last edited by johnny331; 07-09-2007 at 06:53 PM.
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Old 07-10-2007, 09:15 AM   #3
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Johnny331 did a good job trying to explain your problem. I installed engineered hardwood flooring in my dining room and ran it at a 45 degree angle similar to how you are running your panneling, just on the floor.

I just figured my square footage and added 20% for waste to make sure I got enough wood. When making some of your shorter cuts, like in corners, you will end up with fairly long pieces after you make the cut. Fro example, using 8' board and cutting a 6" piece to fit a corner you have a 7'6" piece left. Use this for a row further down the line. This may give you joints in the middle of rows but if thats the look you want then it should work out. If you only want full pieces for each row and no joints then some more planning will be necessary.

You would be surprised how much you waste when making some of the cuts. Its really hard to figure an exact amount, but you sure don't want to make extra trips to get more supplies all the time.
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