Rafter Length

 
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Old 11-07-2008, 07:56 AM   #1
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Rafter Length


Hi Everyone I need some advice on splicing or sistering rafters is this a common practice? I did a search of the site for prior posts and didn't find much. This wiil be my second roof and it looks like the rafters are going to be around 20' just to the top plate .I doint want to use trusses . Any help would be great Keith
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Old 11-07-2008, 08:12 AM   #2
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Re: Rafter Length


I've had framers do this before so we can save on the lumber, we were dealing with 20+ foot lengths and the cost is much greater over 20ft. They just cut a point at the end of one and the reverse on the other, put a block on one side and made sure a brace is directly under the joint.

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Old 11-07-2008, 08:20 AM   #3
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Re: Rafter Length


If you dealt with a real lumberyard and are really a carpenter you would know you can get dimensional lumber in lengths longer than that.

Most lumberyards around here stock up to 24 ft lengths and can get 28 footers.

One dimensional lumber manufacturers list that makes up to 24 footers.

http://www.canfor.com/products/wood/.../dimension.asp
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Old 11-07-2008, 08:29 AM   #4
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Re: Rafter Length


I know we can get long lengths, we do on some homes...but they priced per board foot goes up a lot around here once you break the 20ft length.
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Old 11-07-2008, 08:43 AM   #5
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Re: Rafter Length


Yes the price is higher per bd. ft., but I have never seen where it is that much higher that it would be cheaper to splice and run braces down to a wall. You have to figure in the extra time and what the extra lumber for the braces costs.

Now this is assuming a high pitched roof like a 10 or 12/12. If it is a low pitched roof you would need braces anyway at these lengths.
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Old 11-07-2008, 08:48 AM   #6
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Re: Rafter Length


We've done it on 10 or 12 pitch roofs. And I agree with the added cost in the bracing, etc. But as for labor, I am paying them a lump sum for the job...no matter if they use 24 footers or splice 20 footers. Around here the inspectors look hard for tons of bracing anyways so that isn't as much of an additional cost.
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Old 11-07-2008, 09:07 AM   #7
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Re: Rafter Length


Thanks guys, the pitch is 8 run is 18'. I think I'll price the 20' to see. It would be easier I think but if the price is too much I know I can splice. Monticellohomes the bracing is it always placed over load bearing wall? Looks like i'll have to splice the hips anyway.Keith
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Old 11-07-2008, 11:41 AM   #8
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Re: Rafter Length


Either over a wall or a beam depending on where you are needing to brace and what opportunities you have to brace.
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Old 11-07-2008, 12:23 PM   #9
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Re: Rafter Length


Quote:
Originally Posted by keith tatum View Post
Hi Everyone I need some advice on splicing or sistering rafters is this a common practice?
Yes, if the plans call for it and are designed for it by splicing them over a structural beam or a wall that is designed to handle the roof load when yoiu have a span long enough where you can't get rafters that long, but you don't have that problem, you can get them the length you need..

Quote:
I did a search of the site for prior posts and didn't find much. This wiil be my second roof and it looks like the rafters are going to be around 20' just to the top plate .I doint want to use trusses . Any help would be great Keith
You obviously know by now you don't have to use trusses. Just order the right length because that's the best way to do it. You are not qualified to decide how/where to splice it. Splicing them is ridiculous and you would spend more time and money doing so, especially not knowing where to do so.

Do the right thing and get the right length and be done with it, especially since you don't have a set of plans designed by an Architect or Engineer.
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Old 11-07-2008, 12:44 PM   #10
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Re: Rafter Length


20' is not a problem for rafter lenght. Using a brace (purlin) and kickers down to a bearing wall might let you reduce the size of the rafter.
All this should be calculated by a Structural Engineer.
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Old 11-11-2008, 09:41 PM   #11
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Re: Rafter Length


Looks like i'll have to splice the hips anyway.Keith

How bout a 7.25" or 9.25" LVL for the hips instead of splicing? We use them on long hip and valley rafters. Our yards will deliver 48'ers if we need them. They are pricey, but the time savings and straitness with no cuping is well worth the frustration.
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Old 11-12-2008, 04:59 AM   #12
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Re: Rafter Length


We use LVL's for long hips and valleys, actually for most hips and valleys. Have even used LVL's for long run common rafters.
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Old 11-17-2008, 06:54 PM   #13
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Re: Rafter Length


I-joists work well for long span rafters as well.
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Old 12-28-2008, 07:53 AM   #14
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Re: Rafter Length


If my math doesn't fail me, the 8 in 12 slope over an 18 foot run would require a rafter over 22 feet long. Unless the room arrangements allow for continuous, reliable support for bracing; you will eventually have a wavy roof deck and sagging ceiling joists. You may want to consider I-joist rafters for this job. Install lumber rafter tails to create seat and overhang and you will have a durable system. If you are trying to minimize cost, think ahead about whether it will minimize your reputation if problems arise!!! My biggest question is why you want to avoid trusses. They would give the most strength for the buck and keep room layouts flexible.
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Old 12-28-2008, 07:56 AM   #15
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Re: Rafter Length


Yeah, man, the LVL's work great for hips, but keep 'em dry!
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Old 12-28-2008, 08:34 AM   #16
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Re: Rafter Length


Quote:
Originally Posted by critter View Post
If my math doesn't fail me, the 8 in 12 slope over an 18 foot run would require a rafter over 22 feet long. Unless the room arrangements allow for continuous, reliable support for bracing; you will eventually have a wavy roof deck and sagging ceiling joists. You may want to consider I-joist rafters for this job. Install lumber rafter tails to create seat and overhang and you will have a durable system. If you are trying to minimize cost, think ahead about whether it will minimize your reputation if problems arise!!! My biggest question is why you want to avoid trusses. They would give the most strength for the buck and keep room layouts flexible.
Sagging ceiling joists? I-Joist rafters for 21' +? 29" LVL hips? You should really be thinking about your reputation right now???? Have you ever heard of a roof purlin??? I have always wondered why we have to flush the mind of the techies??? It's sad but now I know!!!!
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Old 01-02-2009, 10:32 PM   #17
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Re: Rafter Length


Yes, borat, I've heard of purlins. They go ACROSS rafters to support decking or roofing. Perhaps you were referring to under-purllins, which SUPPORT rafters? I was a farm kid and I could build a barn; mortised, tenoned and pinned with chinkapin oak in my sleep. I could pretty well figure out the placement of the under-purlins, jacks and knee logs. I worked construction for over 20 years before starting to teach because I witnessed too many idiotic mistakes made by people who couldn't or wouldn't think things through BEFORE bullding - and which were totally preventable with a bit of "techie" wisdom. I may have wrongly inferred that the gentleman with the rafter span concerns had issues with support due to room arrangement. Your under-purlin idea is standard practice and a no-brainer when such support can be used. An open room area could be spanned with a support girder of any description appropriate to the span - but weight will transfer to the ends of that span and through to the floor. If the floor in that area is not adequately supported, the entire roof deck section will sag - AND affect the room finishes, etc. below. Construction techies and tards both eat wood and **** splinters - you outta know that, even though you're just a kid. :-)
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Old 01-03-2009, 01:46 AM   #18
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Re: Rafter Length


dam guys, just get the right size lumber! If the span is so great, the guy who drew the picture usualy gives u a place to put a pony/knee wall over a bearing wall/partition to transfer the weight down to the main girder system using 2 smaller lengths,the cost of the longer boards? If the rafters r that big that ur worried bout the cost, the house is usualy very expensive and the xtra cost will seem like nothing when u get the price 4 the interior trim package. just remember if it ain't on the plans get the arch/eng to sign off on it, unless u want to fix it 4 free if it fails
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Old 02-05-2009, 05:34 AM   #19
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Re: Rafter Length


Hey Keith, When your figuring the longer lumber vs. splicing, dont forget to figure in the extra labor for splicing.
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Old 02-05-2009, 11:40 PM   #20
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Re: Rafter Length


Quote:
Originally Posted by keith tatum View Post
Thanks guys, the pitch is 8 run is 18'. I think I'll price the 20' to see. It would be easier I think but if the price is too much I know I can splice. Monticellohomes the bracing is it always placed over load bearing wall? Looks like i'll have to splice the hips anyway.Keith
No you can't ever splice a rafter without a qualified professional doing load calculations!!! Especially on your SECOND ROOF!!! Don't try to save a few dollars today so your VICTIM will need to spend thousands reframing in a few years.

This kind of thinking is why people think contractors are idiots and crooks!

Imagine a lead carpenter on his second roof. What is our industry coming to?

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