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-   -   Roof Framing a 18 x 22 shed (http://www.diychatroom.com/f9/roof-framing-18-x-22-shed-64353/)

BatmanDIY 02-13-2010 02:06 PM

Roof Framing a 18 x 22 shed
 
Hi i am looking to build a shed by 18 x 22. i got some books about roof framing since i never done that before. i figured out all the measurements for my roof and rafter lengths and everything. i am doing a 6/12 pitch roof and going to use 2x6 for rafters. my only question is what about the ridge beam. where can i go to find out what dimension of wood that is good for a ridge beam thats going to be 22' long. can i use a 2x6 or a 2x8? Do i need a engineer lumber for this? can someone please help me out with this. thank you

mike

Scuba_Dave 02-13-2010 03:22 PM

With rafter ties the ridge beam is not a structural element
As long as the rafters land at the same opposing point on the ridge beam it just needs to be large enough for the rafter face to land

BatmanDIY 02-13-2010 03:28 PM

i want to make sur ei am understanding this correct so if i use rafter ties on all my rafters i can just use a 2x6 for a ridge beam? thank you

mike

Scuba_Dave 02-13-2010 03:31 PM

No, when you cut a rafter at an angle the resulting "face" of the 2x6 rafter end will be longer then 5.5"
With my 5/12 roof one size higher would work
So with 2x6 rafters you would need a 2x8 ridge beam at the very least

Yes, as long as you have rafter ties the ridge beam is a ridge board

BatmanDIY 02-13-2010 03:57 PM

ok. yes thats what i meant a 2x8 ridge. ok thats all i needed to know so i know how to build this. thank you so much for your help i been looking for this kind of info all over for awhile know i can move onto the next stage. which is waiting for the snow to leave so i can start to build. thanks again

mike

BatmanDIY 02-13-2010 03:59 PM

im sorry that was my other question what size can i use for rafter ties? or can i just use collar ties? i want to put some kind of rafter ties up so i cna store a little bit up their.

jlhaslip 02-13-2010 04:00 PM

ridge boards (this is not a ridge 'beam') are typically sized 1 size larger than the rafters.
in your case, make it a 2 x 8.
line the long point of the rafter to the edge of the ridge board and set them in pairs.
watch that the setting of the rafters doesn't push the ridge out of straight.
set each end and a pair in the middle to help keep it straight.

Gary in WA 02-13-2010 06:01 PM

I suggest you clear this with your local Building Department. And your Homeowners Insurance carrier for liability and protection.

The size of your building is about twice bigger than our minimum to build without a permit, this varies per locale.

IRC, 2003, requires the ridge board to be minimum 1x & full depth of cut rafter... 802.3 UBC- 2320.12.3

Definitely use rafter ties (1x4, 4'o.c.) and notch a heel bearing seat cut on the wall: 802.3.1 “Toe-bearing rafters
One of the last things done on an addition is framing the roof. To tie a new roof into an existing roof line, rafters often bear on the toe rather than the heel of the seat cut or are notched too deeply over the top plate (Figure 4). These situations weaken the rafter at the bearing point and can split the rafter. Always try to bear the rafter on the heel of the seat cut. This does two things. It means the full depth of the rafter is bearing on the top plate, so you don't have to worry about the rafter's splitting. It also means you can get more insulation over the top of the outside wall, providing much better energy efficiency.”
Read the rest here: http://www.housingzone.com/proremodeler/article/CA462902.html#

Add the correct amount of nails at the rafter/tie connection: http://www.engineersedge.com/civil_e...onnections.htm

Hope this helps you build!

Be safe, Gary

Daniel Holzman 02-13-2010 06:16 PM

Since you have a book on framing, you probably know this already, but just in case. A rafter tie is defined as a structural element that connects the ends of both rafters to each other. Typically this is a joist that spans between the walls, and is nailed or connected via a hanger to the rafters where the rafters meet the walls. It is NOT PERMISSIBLE to substitute a collar tie for a rafter tie. The collar tie is typically a light (read 1x4 or 1x6) element attached at approximately 2/3 of the distance from the floor to the peak of the roof, and connects opposite pairs of rafters.

The purpose of a collar tie is to equalize loading on the rafters during unusual load conditions such as uplift from wind, or shaking from earthquakes. A lot of people mistakenly think that the collar tie helps resist outward thrust of the rafters on the walls, however this is not the case, due to the small size, weak connection to the rafters, and location in the upper third of the roof. The floor joist (rafter tie) resists outward thrust of the rafters against the walls.

If you install a ridge beam (as opposed to your intention to install a ridge board), you will eliminate outward thrust of the rafters, which in some cases allows you to eliminate both the collar ties and the floor joists, however you always need to check code for your area to see if this is permissible. A ridge beam is a structural element typically supported at either end by a column or wall, and supported at intermediate points if necessary. This is probably irrelevant for your project, since you are planning to frame using conventional rafters, however if you are thinking about cathedral ceilings a ridge beam is commonly used.

BatmanDIY 02-13-2010 06:45 PM

wow this is a lot to take on. i know im going to have to apply for a permit an plan on doing so but i wanted to get all my plans correct so they can quickly pass the plans and also i want to get the plans right know so i know about how much this is going to cost me to build. so i can do a 2 x 8 ridge board and what size rafter ties should i use. can i get away with 2x6 rafter ties or have to go with 2x8. i was thinking of putting collar ties in and rafter tie. i figure ill put both in and it would be stronger. any suggestions and please help me with the last questions on how big should my rafter ties be? thank you

mike

Daniel Holzman 02-13-2010 06:53 PM

If the rafter ties are floor joists, they are sized based on the floor loading. Check your local code for minimum allowable dead and live load for floor loads. If you are not planning to put a floor on the joists, you should check code for minimum sizing of the rafter ties. I have never designed a project with zero floor load, so this is new to me.

BatmanDIY 02-13-2010 06:58 PM

what you mean by zero floor load. im just going to use that area to store minimal amount of stuff. like spare wood and stuff like that if anything at all. so on monday ill check what the code is. how do i do that do i just go to town hall and ask for the code book or something?

mike

Gary in WA 02-13-2010 08:01 PM

It depends on what you want to store up there. In the middle of my post #8, I quoted the IRC requires a 1x4 for a rafter tie, every 4' on center. OR, you can use ceiling or floor joists that substitute for rafter ties, and you can load them: example: http://www.colonie.org/forms/building/bdspanab.pdf They all serve to keep the walls from spreading.

It also depends on what year's code book you are under.... give them a call, or check on-line.

Be safe, Gary


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