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Link44
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# Posted: 30 Aug 2022 12:22am
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I finally started my cabin this weekend. I have a question about the ridge board. The cabin will be 24 feet long with a loft over 10 feet of the back end. I dont have 24 foot lumber and I have read that the ridge board will need support for the roof and at the joint. What is the best way to tie the 2 boards together to get the 24 foot length?
Thank you
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Brettny
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# Posted: 30 Aug 2022 05:14am
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You can scab a piece on both sides that's the same height. But this is if your doing a ridge board and not a ridge beam.
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ICC
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# Posted: 30 Aug 2022 01:55pm - Edited by: ICC
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If it is a ridge BOARD, it serves no real structural purpose. It holds the spacing of the rafters and helps with nailing the rafter points together. A ridge BEAM is a whole different thing.
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NorthRick
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# Posted: 30 Aug 2022 05:00pm
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What ICC said. Need more details before anyone could give a constructive answer.
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ICC
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# Posted: 30 Aug 2022 07:14pm
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https://www.techsupport.weyerhaeuser.com/hc/en-us/articles/207291947-Ridge-Beam-vs-Ri dge-Board-
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Link44
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# Posted: 31 Aug 2022 12:05am
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I have read about the differences in board vs beam. It is a ridge board, single 2x8, to have a place to nail the 2x6 rafters to. I was searching for the best way to join the two 2x8's end to end to get 24 feet in length. I had thought about scabbing 4 foot sections of 2x8 on both sides of the joint but wanted to check in here first. I will have a post under the joint.
Thanks
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razmichael
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# Posted: 31 Aug 2022 07:11am
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Quoting: Link44 I will have a post under the joint
Is the post doing something else? As noted, there is no use/value of a post under a ridge board (joint or not). Just trying to get a clearer vision here.
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Link44
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# Posted: 31 Aug 2022 08:22am
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I was hoping the post would support the ridge board at the half way point in the roof so the walls won't push out. The loft floor should tie the walls for the back 10 feet of the cabin. Does this sound reasonable? I'd rather not have rafter ties. I'd like to leave the ceiling open.
Thanks
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razmichael
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# Posted: 31 Aug 2022 09:16am
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There are people here with way more knowledge than I have but I really think you are mixed up on the role of a ridge board. As noted they have no structural value at all and only make it easier to put up rafters (which along with rafter and collar ties provide the various structural functions). Sounds more like you want cathedral type trusses or switch to a Ridge Beam which has a very different role.
I used a 24’ LVL beam (made up of 3 LVLs) with a support (actually a wall) at 16’ to cover the 24’ span (main floor is 16x16 with 8’ extension over a deck that includes an upstairs loft). Might have been able to span the full distance with bigger LVLs but did not need to. Gamble style rafters hung on the beam (stanly hangers). This provides open ceiling and lots of headroom in the loft (16x10) and I can stand in about 14x10 of the space).
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ICC
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# Posted: 31 Aug 2022 09:23am
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Quoting: Link44 I was hoping the post would support the ridge board at the half way point
And what supports the post loads?
Rafter ties are supposed to connect to the rafter tails at the level of the wall top plates. The ties are fastened (nailed) to the rafters with a prescribed # of nails that varies with dimensions and loads. The rafter ties can also be used as ceiling joists and floor joists for an upper level and are usually secured to the wall top plate with a hurricane tie. (And note that collar ties are Not rafter ties)
Rafters with a rafter tie and form a rigid triangle. It is a free engineered solution when built as prescribed by bldg code. that makes a no sag roof. Anything else is an experiment. Results can sometimes be acceptable, or not.
The open ceiling you want is why ridge beams are used.
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gcrank1
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# Posted: 31 Aug 2022 09:31am
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The 'ridge board' is under compression by the rafters, and wall pushout is not because of the ridge board.
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NorthRick
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# Posted: 31 Aug 2022 05:07pm - Edited by: NorthRick
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Quoting: Link44 I'd like to leave the ceiling open.
Then you need a ridge beam. It needs to be sized to support the roof loads. Any posts and the walls at either end of the cabin also need to be designed to handle the expected roof loads.
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curious
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# Posted: 31 Aug 2022 05:25pm
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NorthRick is correct
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Link44
Member
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# Posted: 31 Aug 2022 05:30pm
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Ive read that rafter ties are effective as long as they are in the bottom 1/3rd of the rafter correct? So with a 8/12 roof as long as the rafter tie is in the bottom 21 inches that would work.
My neighbors have an A-frame that has the walls tied every other rafter but they have a tie on each side of the rafter. So the rafter is sandwiched between 2 ties.
I'd like the ceiling open but I have myself in a time/weather crunch now. I should have asked more questions sooner so I may change plans to make sure the building will be structural sound. Would something like that work here instead of a beam?
Thanks
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Link44
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# Posted: 2 Sep 2022 09:55pm
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Does evey rafter need to be tied? I have seen that they can be installed 4ft oc. I read the building code section on roofs and it was not clear. It listed collar ties every 4ft but I didnt see specifics on whether or not ever rafter had to be tied. I did find the nailing schedule and noticed the steeper the pitch the less nails required. This will be a 8/12 roof.
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ICC
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# Posted: 2 Sep 2022 10:26pm
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IRC section R802.5.2.2 states rafter ties shall be spaced a maximum of 24" OC. So in the real world most of the time you end up with a rafter tie for each rafter pair.
Collar ties may be replaced by over the ridge metal straps.
The method illustrated in the screenshot seems a little unusual to me. Running the ceiling joists as illustrated would require some method of supporting the ceiling joists, such as a beam or structural wall at each end. Much more normal practice would be to combine the purpose of the rafter tie and the ceiling joist into the same member; call it a ceiling joist. Support the ends of the ceiling joists on the sidewall top plates and nail the rafters to the joists as specified in R802.5.2.
Are you using the actual IRC code as listed on the International Residential Code (IRC) website? Their pages get updated from time to time
2021 version
2018 version
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ICC
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# Posted: 2 Sep 2022 11:01pm
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Quoting: Link44 I did find the nailing schedule and noticed the steeper the pitch the less nails required.
Which is cause as the pitch gets steeper more of the roof load becomes a vertical load on the side walls and less outward horizontal push load. So fewer nails are required for the heel joint connection.
Re, the previous post.... an engineer may sogn off on installing the rafter ties on every other rafter pair if the ties sre doubled or increased in tension load capacity. The IRC has many instances where "other approved methods" may be used. That approval implies engineering.
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Link44
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# Posted: 2 Sep 2022 11:55pm
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I didn't find the 24oc part but I do now see the ever rafter part. It also states that other approved methods are permitted. I am finding what other methods are approved.
This cabin is not getting inspected but I do want it to be safe.
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ICC
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# Posted: 3 Sep 2022 08:52am - Edited by: ICC
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Quoting: Link44 It also states that other approved methods are permitted. I am finding what other methods are approved
That is any solution provided by a state licensed engineer who will provide a drawing with the design spec's and apply their professional stamp.
The screenshot is from the IRC website I linked, 2021. States can make changes. At times little details get lost and that can cause confusion and frustration, but the absence of a detail does not change the science behind the engineering.
I like safe and like codes as there is science and safety concerns behind what is spelled out.
I checked and that 24" detail was missing from some earlier versions. But every roof plan I have ever worked off has had a rafter tie or ceiling joist at every rafter and those were usually 24" or in some cases, 16" apart. Most of those were in code areas or stamped by an engineer.
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Link44
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# Posted: 3 Sep 2022 11:51am
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My building will be 16oc from top to bottom to create a solid path to the ground. If I have to tie every rafter I will. I realise you are not an engineer and I do appreciate the advice. What do you think about double rafter ties every other rafter? I am thinking I could box them in and make them look like beams. They will not have a "ceiling" attached to them.
Thanks
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ICC
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# Posted: 3 Sep 2022 02:41pm - Edited by: ICC
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"I realise you are not an engineer and I do appreciate the advice.". If I was I would not be giving away professional advise on a free forum. 
With your studs, etc. at 16" OC, my semi-educated guess is that doubling the rafter ties on every other rafter pair should be fine. You could increase the nail joint strength by a considerable amount by (1) driving the heel joint nails at different angles and (2), by using nails that will penetrate through and clinching the points over across the grain. I made a clinching iron similar to what wooden boat builders use, but one is not necessary for s one-off job. That adds considerable strength to joint separation.
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Link44
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# Posted: 3 Sep 2022 11:15pm
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That sounds good. Would substituting a large bolt with washers in each connection for some of the nails work to increase the strength of the joint?
Thanks
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ICC
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# Posted: 4 Sep 2022 09:20am
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Yes and no. The bolt can have much more tensile and shear strength than nails. The washers make it virtually impossible to have the connection fail by fastener withdrawal. However, if the wood cracks or somehow fails at/near the bot hole the whole connection could fail quickly. Using a group of nails distributes the load out over a broader area. Nails also will deform slowly if they receive heavy loads rather than fail rapidly as fasteners that are hardened will do. Several structural-rated screws might be a better addition or substation than a bolt.
Clinched nails are used in pallet construction which is why they are a bear to dismantle. Those nails are power-driven in a device that has a steel plate on the side where the nail points penetrate through and is bent over.
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Link44
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# Posted: 4 Sep 2022 10:55am
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I have tried to nicely disassemble pallets before, near impossible.
I will get some 3 1/8 GRK's to add to the connection. I really like those screws. I used some as well as nails to build up my 4 wide 2x8 beams for under the floor joists.
Thank you for your help.
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