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Old 08-07-2012, 12:57 PM   #16
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building 18x18 cottage need help 12 12 rafters


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Originally Posted by framer52
Sounds like it, Joe.
It could be 18'1" including the sheathing. He has to have a ridge beam too for a cathedral ceiling unless he's using rafters ties for a clipped ceiling...but he didn't say that.

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Old 08-07-2012, 01:09 PM   #17
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building 18x18 cottage need help 12 12 rafters


Thanks joe. My local lumber yard wanted me to order all 16 footers. Glad i found the forum.
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Old 08-07-2012, 01:25 PM   #18
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building 18x18 cottage need help 12 12 rafters


do you know what your ground snow load is if any? what about any wind loads? what species of wood are you using?

you said 12:12 pitch cathedral roof, I take it you mean without any ceiling joists/rafter ties so that your ridge will have to support 9' of tributary load from the roof?
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Old 08-28-2012, 07:37 PM   #19
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building 18x18 cottage need help 12 12 rafters


Rafter help. Can anyone help with the width of rafter boards
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Old 08-28-2012, 08:01 PM   #20
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building 18x18 cottage need help 12 12 rafters


this link will take your to the 2009 International Residential Code Rafter Tables. You will need to find the species of wood and grade your for your rafters, including your live and dead loads. This will give you the maximum span for your rafters

http://publicecodes.cyberregs.com/ic...9_8_par025.htm
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Old 08-28-2012, 08:13 PM   #21
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building 18x18 cottage need help 12 12 rafters


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Rafter help. Can anyone help with the width of rafter boards
as others have mentioned, exact dimensions are needed. At the wall top plates what are the measurements between the outside walls, inside of wall to inside of wall? Is it a 2x4 wall or 2x6 or??
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Old 08-28-2012, 08:16 PM   #22
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building 18x18 cottage need help 12 12 rafters


Its a 18 x 18 square. And they are 2x6 walls
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Old 08-28-2012, 08:28 PM   #23
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building 18x18 cottage need help 12 12 rafters


will you have ceiling joists installed?
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Old 08-28-2012, 08:31 PM   #24
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No. All exposed. No loft.cathedral cielings
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Old 08-28-2012, 08:33 PM   #25
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building 18x18 cottage need help 12 12 rafters


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No. All exposed. No loft.cathedral cielings
That changes EVERYTHING!

Ridge beam is necessary. If you don't know what this means, you are in over your head. Get someone qualified to work on this.
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Old 08-28-2012, 08:36 PM   #26
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building 18x18 cottage need help 12 12 rafters


I know what a laminated ridgebeam is. I was told by the lumber yard all i will need is a 2x12x20 ridge beam. Which i know is not correct.
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Old 08-28-2012, 09:15 PM   #27
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building 18x18 cottage need help 12 12 rafters


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I know what a laminated ridgebeam is. I was told by the lumber yard all i will need is a 2x12x20 ridge beam. Which i know is not correct.
not even close for a structural ridge beam ..... it would work if you were installing ceiling joists or rafter ties where it would simply be a ridge board.

you'll be looking at something like a 2-ply 16" LVL or 3-ply 14" LVL and you'll have to account for somewhere around 3800 pounds of load at each end of the ridge beam.

Have the lumber yard contact their rep for their engineered wood products to determine the actual size of beam needed and provide engineer's certified calculations for the building official (if needed). Engineered wood products fall outside the prescriptive nature of the building code.

You never posted what your ground snow load was so the actual load may vary from what I showed. You'll need to size the support column based upon the species of wood used for your sill plates so that you do not crush the wood fibers and cause the column to settle.

I typically install collar ties directly under the ridge beam attached to the sides of the rafters at each pair of rafters. Either that or Simpson Strong-Tie LSTA24 strap ties over the roof sheathing to connect opposing pairs of rafters together.

Just my thoughts ....
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Old 08-28-2012, 09:29 PM   #28
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Thank you for your help.
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Old 08-29-2012, 07:41 AM   #29
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not even close for a structural ridge beam ..... it would work if you were installing ceiling joists or rafter ties where it would simply be a ridge board.

you'll be looking at something like a 2-ply 16" LVL or 3-ply 14" LVL and you'll have to account for somewhere around 3800 pounds of load at each end of the ridge beam.

Have the lumber yard contact their rep for their engineered wood products to determine the actual size of beam needed and provide engineer's certified calculations for the building official (if needed). Engineered wood products fall outside the prescriptive nature of the building code.

You never posted what your ground snow load was so the actual load may vary from what I showed. You'll need to size the support column based upon the species of wood used for your sill plates so that you do not crush the wood fibers and cause the column to settle.

I typically install collar ties directly under the ridge beam attached to the sides of the rafters at each pair of rafters. Either that or Simpson Strong-Tie LSTA24 strap ties over the roof sheathing to connect opposing pairs of rafters together.

Just my thoughts ....

Exactly what I was thinking, a good 2x6 or 2x8 collar tie butted up to the underside of the ridge or down below the ridge some and nailed with a precise nailing pattern to the rafters...
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Old 08-29-2012, 07:58 AM   #30
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building 18x18 cottage need help 12 12 rafters


I typically use a 2x6 collar tie since our exterior wall are 99% of the time 2x6, why waste scraps?

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