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Ridge board or ridge beam?

mtlogcabin

mtlogcabin

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Question came up about ridge beams versus a ridge board.

Hand framed shed or garage typically we see a ridge board and collar ties installed face plate connectors (bottom picture)

If a contractor uses a top flange hanger (top picture) and collar ties does that change the ridge board to a ridge beam and need to be properly sized?

Some here say because the rafter does not bear on the top of the ridge it does not add an additional loading and therefore is not a beam.

Any thought on this?

46 lbs snow loads we do want to get it correct
 
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Does the framed element [ i.e. - your Ridge Board ]

fit snuggly [ on 3 sides ] in to the top hanger ?

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With a ridge board only, the rafters "lean" against each other. To get a good visual of this, put 2 pencils on your desk and lean them up against each other. If you let go of them, they fall.Now add an imaginary ridge board that keeps 'em from falling over sideways, but doesn't hold the end (peak) up. Now the pencils are leaning against each other and can't fall over. But the bottoms of the pencils will probably slide out and they'll fall anyway.

Now add a ruler to the mix - Imagine it's a ceiling joist. The bottom end of the pencils/rafters are fastened to the ruler/ceiling joist to keep them from sliding out. And the ridge board keeps them from falling over.

Using the pencils leaned against each other again, imagine having a ruler as a ridge beam. The ruler/ridge beam is supported on each end by something like a coffee cup. Fasten the pencils to the ruler with some super glue, and you've got a solid structure again. No need for ceiling joists.
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http://forums.finehomebuilding.com/breaktime/construction-techniques/ridge-board-vs-beam
 
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From the `12 IRC, Section R802.3 - Framing details:

"Rafters shall be framed to ridge board or to each other with a gusset plate

as a tie......Ridge board shall be at least 1-inch (25 mm) nominal thickness

and not less in depth than the cut end of the rafter........At all valleys and

hips there shall be a valley or hip rafter not less than 2-inch (51 mm)

nominal thickness and not less in depth than the cut end of the rafter.

Hip and valley rafters shall be supported at the ridge by a brace to a bearing

partition or be designed to carry and distribute the specific load at that point.

Where the roof pitch is less than three units vertical in 12 units horizontal

(25-percent slope), structural members that support rafters and ceiling

joists, such as ridge beams, hips and valleys, shall be designed as beams."

IMO, ...I think that the top ledger bracket [ in your pics. ] will work,

and not increase the loading of the ridge board.

Also, ...if you DO consider your Ridge Board to be a Ridge Beam, you would

[ technically ] have to install additional framing underneath each end of the

"Ridge Beam" to increase the support for the additional psi loading.



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Without rafter ties or ceiling joists tied to the rafter heel at top plate, the ridge becomes a beam requiring load capacity and end support.
 
Also, ...if you DO consider your Ridge Board to be a Ridge Beam, you would[ technically ] have to install additional framing underneath each end of the

"Ridge Beam" to increase the support for the additional psi loading.
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That has been some of the concerns that have been brought up

Roofs are typically 4/12 to 6/12 pitch so a ridge board has been quite common around here.
 
Roof pitch below 3" and lack of rafter tie is what triggers a ridge to become a beam.

The top flange hanger would not work well at all. There would be a flange on top a flange and the metal at the sides gets in the way of nailing the rafters to the ridge. The seat is not skewed so,it has to be let in. So whether it changes up the loading or not wouldn't be an issue for me because I wouldn't approve it to begin with.
 
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ICE said:
Roof pitch below 3" and lack of rafter tie is what triggers a ridge to become a beam.The top flange hanger would not work well at all. There would be a flange on top a flange and the metal at the sides gets in the way of nailing the rafters to the ridge. The seat is not skewed so,it has to be let in. So whether it changes up the loading or not wouldn't be an issue for me because I wouldn't approve it to begin with.
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Or a volume roof design without ties
 
mark handler said:
Or a volume roof design without ties
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I've not heard the term"volume roof design" before now. What I meant was that any roof below 3" pitch is engineered with a probable beam. Any roof pitched 3" or greater without rafter ties is engineered with a probable beam.
 
Don't confuse a collar tie with a rafter tie. A collar tie is generally used to resist uplift and is installed in the upper third of the attic space. A rafter tie is used to resist rafter thrust and is installed in the lower third of the attic space. It is most effective when installed at the heel and less effective as it is raised above the heel (to the max lower third height). Collar ties are installed every 4'. Rafter ties are installed on every rafter. Code requires rafter ties OR a ridge beam so if your "ridge" is not capable of carrying the tributary load from the rafters then you must have a rafter tie on each rafter in the lower third of the attic space. Keep in mind though that as the rafter tie travels up from the preferred placement at the heel joint it will reduce the rafter span (see the span tables and notes for the formula). Of course all this is prescriptive, and maybe a lot of over-kill for a shed. When you use a rafter tie you are basically creating an opposing force at the top and the tension will tend to hold the top of the rafters tight but when you don't the opposing force is eliminated as the bottom of the rafter will thrust out and the top will come down. Think of a sawhorse without a gusset.
 
Thanks Glenn. That is an informative article. I didn't know about increasing the rafter size if the rafter tie is raised above the wall plate. Can I can go home now because I have already learned something new for today?

You should place that article at the useful links thread. Do you have other articles to share? Well then I took a look at the website for your link. There is a forum. It is pay to play all the way. The forum is pretty bland. Does the ICC own the site? Another thing that I noticed is that I can't print the article.
 
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Thanks ICE,

The Journal of Light Construction is a trade journal (primarly targeted to contractors and "best practice") I worked with them to create a regular column called "Codes Eye View" so some code can get squeeked in every edition. I work very hard to get contractors interested in learning code. I've got some great topics lined up this year. The link is to their online version of the magazine. They also have a trade show, the JLCLive. It's not ICC, it's owned by a big media corporation.

Here is a link to all the articles I've written for them so far: http://www.jlconline.com/find-articles.aspx?byline=Glenn+Mathewson
 
I am subscriber to JLC. Pretty decent mag but seems to have eclipsed the 50% ads to info mark. I do see your column pretty regularly Glenn.
 
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"This was an awful lot of talk for a simple 'wrong hardware Mr. Contractor' kind of post."
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That's what we do here Big John, ergo this emoticon - - - > :beatdhrs Plus we DO like the entertainment value ! :mrgreen:



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