# Skylight framing- cutting one rafter



## Aunty Lulu (Oct 12, 2020)

Hi -I am framing a skylight and can not find a framing detail in the code except one for metal rafters. Figure R804.3.5(1)
My rafters are 2" x 6" on 20" centers with a 16' span with a 12:12 pitch. I will be removing one rafter and putting in a 30" wide x 39" tall skylight.
Can anyone steer me to the proper code for this? I am in the Denver CO area.

I would appreciate any input.

Thanks, Aunty Lulu


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## mark handler (Oct 13, 2020)




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## ADAguy (Oct 13, 2020)

As usual MH, your files contain many ref's, thanks for sharing.


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## my250r11 (Oct 13, 2020)

I believe he is looking for wood detail. I would except if 2 x 6 joist hangers used  in same place on the wood as is in the metal detail.


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## e hilton (Oct 13, 2020)

Don’t the rafters that carry the headers need to be doubled?  If you look at the metal detail carefully, they have nested the second member into the first ... its not obvious.


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## classicT (Oct 13, 2020)

Aunty Lulu said:


> Hi -I am framing a skylight and can not find a framing detail in the code except one for metal rafters. Figure R804.3.5(1)
> My rafters are 2" x 6" on 20" centers with a 16' span with a 12:12 pitch. I will be removing one rafter and putting in a 30" wide x 39" tall skylight.
> Can anyone steer me to the proper code for this? I am in the Denver CO area.
> 
> ...


See _IRC Section R802.9_ as follows:

*R802.9 Framing of Openings*
Openings in roof and ceiling framing shall be framed with header and trimmer joists. Where the header joist span does not exceed 4 feet (1219 mm), the header joist shall be permitted to be a single member the same size as the ceiling joist or rafter. Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. Where the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. _Approved_ hangers shall be used for the header joist to trimmer joist connections where the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).


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## ICE (Oct 13, 2020)

classicT said:


> See _IRC Section R802.9_ as follows:
> 
> *R802.9 Framing of Openings*
> Openings in roof and ceiling framing shall be framed with header and trimmer joists. Where the header joist span does not exceed 4 feet (1219 mm), the header joist shall be permitted to be a single member the same size as the ceiling joist or rafter. Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. Where the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. _Approved_ hangers shall be used for the header joist to trimmer joist connections where the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).


And that folks is the bare minimum.


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## mark handler (Oct 14, 2020)

my250r11 said:


> I believe he is looking for wood detail. I would except if 2 x 6 joist hangers used  in same place on the wood as is in the metal detail.


Doesn't matter its a graphic, DOES THIS MAKE IT ALL BETTER 
use LTP or A35 at all side
​


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## ICE (Oct 14, 2020)

Aunty Lulu said:


> My rafters are 2" x 6" on 20" centers with a 16' span with a 12:12 pitch.


Another 8" and you would be required to double the trimmers.  Knowing that the rafters are over-spanned already....code is the minimum allowed ....what does that tell you?


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## e hilton (Oct 14, 2020)

Aunty Lulu said:


> My rafters are 2" x 6" on 20" centers


That’s an odd number.  They could be 19.2” oc (the black diamonds) but not many people use that spacing.


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## ICE (Oct 14, 2020)

e hilton said:


> That’s an odd number.  They could be 19.2” oc (the black diamonds) but not many people use that spacing.


Ever since the fourth grade, 20 has been an even number.


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## my250r11 (Oct 14, 2020)

e hilton said:


> Don’t the rafters that carry the headers need to be doubled?  If you look at the metal detail carefully, they have nested the second member into the first ... its not obvious.


I did see that. I assumed it was a track to be able to screw the clips on the open side.


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## e hilton (Oct 14, 2020)

ICE said:


> Ever since the fourth grade, 20 has been an even number.


I didn’t make it past the 3rd grade.


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## MACV (Oct 15, 2020)

If the rafter span (horizontal distance from exterior wall to the ridge board) is 16 ft, the roof is *seriously* under structured.  Perhaps 16 ft is the width of the building and the span is 8 ft.
If that's the case, the location in CO is important but to be safe I recommend doubling the rafters unless there're rafter ties just above the skylight.
You really need more information to design a roof in CO regardless of what the code says.


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## Aunty Lulu (Oct 19, 2020)

MACV said:


> If the rafter span (horizontal distance from exterior wall to the ridge board) is 16 ft, the roof is *seriously* under structured.  Perhaps 16 ft is the width of the building and the span is 8 ft.
> If that's the case, the location in CO is important but to be safe I recommend doubling the rafters unless there're rafter ties just above the skylight.
> You really need more information to design a roof in CO regardless of what the code says.


Thanks- The rafters are indeed 16' from floor to ridge board (what I can measure with the room finished). The house is 115 years old so it must be working- back then they did what they did. The roof is 12:12 so maybe that helps. I did see on one place in the building code that one species is ok for that span but not the spacing. So, I will double the rafters and put in some beefy headers above and below the skylight to be safe. Thanks for your input.


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## Aunty Lulu (Oct 19, 2020)

my250r11 said:


> I did see that. I assumed it was a track to be able to screw the clips on the open side.


So where do they have a diagram of the wood rafter spacing (doubling) for skylights?


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## Aunty Lulu (Oct 19, 2020)

Aunty Lulu said:


> So where do they have a diagram of the wood rafter spacing (doubling) for skylights?


Sorry I am reading the post from bottom to top so missed the diagram.


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## Aunty Lulu (Oct 19, 2020)

classicT said:


> See _IRC Section R802.9_ as follows:
> 
> *R802.9 Framing of Openings*
> Openings in roof and ceiling framing shall be framed with header and trimmer joists. Where the header joist span does not exceed 4 feet (1219 mm), the header joist shall be permitted to be a single member the same size as the ceiling joist or rafter. Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing. Where the header joist span exceeds 4 feet (1219 mm), the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the ceiling joists or rafter framing into the header. _Approved_ hangers shall be used for the header joist to trimmer joist connections where the header joist span exceeds 6 feet (1829 mm). Tail joists over 12 feet (3658 mm) long shall be supported at the header by framing anchors or on ledger strips not less than 2 inches by 2 inches (51 mm by 51 mm).


Thank you for such detail classicT 
My roof window will start 7' from the bearing point of the rafter, roughly in the middle of the 16' span (I am not at the house so can't measure for sure), so does that knock me out of:

Single trimmer joists shall be permitted to be used to carry a single header joist that is located within 3 feet (914 mm) of the trimmer joist bearing.

My plan is to double the trimmer joists but not the one joist that I cut out. Do you think that will work?

Sorry, in previous posts, I wasn't using the right name for the trimmer joists.

ALu


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## Aunty Lulu (Oct 19, 2020)

mark handler said:


> Doesn't matter its a graphic, DOES THIS MAKE IT ALL BETTER
> use LTP or A35 at all side
> View attachment 7050​


Thank you for the info on the ties and yes, a diagram does "make it all better". 
So, this summer at our museum we had an exceptional wind event and lost a roof (with all the trusses). I overheard the contractors that came (to revel in the fact that THEY hadn't built it), say that the builder was supposed to use nails not screws for those strong ties. Is that correct? I would MUCH rather use screws if it is ok (i'm really not enthusiastic about having 115 years worth of dust and mouse crap raining down on me with all that hammering- I'll get enough with an impactor). I did see in the code book that they reference nails and how many (when not using ties) but nothing about screws.

Thanks, and please don't get mad at what might be to you a stupid question... up here on a ranch Wyoming, we kind of just use common sense because there are no inspectors to speak of- but that house is in Denver...


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## Paul Sweet (Oct 20, 2020)

Simpson does make screws that can be used with their connectors:








						Screws and Nails
					

Screws and Nails | Simpson Strong-Tie




					www.strongtie.com
				




Do NOT use cabinet screws, drywall screws, decking screws, or other stock screws from big-box stores, because many of them are brittle and will snap with repeated bending under cyclical load.


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## MACV (Oct 20, 2020)

"16' from floor to ridge board" is not the dimension of the rafter span.  If this is a simple gable roof, what is the total width of the house?


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## MACV (Oct 21, 2020)

If the 2x6 rafters slope 12 in 12 and are 16-0 long measured *along* the rafters, then the horizontal *span* is about 11-2 and the width of the house would be about 22-4.


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## Aunty Lulu (Oct 22, 2020)

Paul Sweet said:


> Simpson does make screws that can be used with their connectors:
> 
> 
> 
> ...


Thank you- I found the strong tie site and found the right screws: Strong-Drive® SD CONNECTOR Screw SD 9  1.5"
Deck screws are exactly what the contractor used on the building that lost it's roof.


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## Aunty Lulu (Oct 22, 2020)

MACV said:


> "16' from floor to ridge board" is not the dimension of the rafter span.  If this is a simple gable roof, what is the total width of the house?


Sorry I'm not there now to get an exact measurement but based on geometry, it should be around 22-23'


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## Aunty Lulu (Nov 21, 2020)

So, here is the framing that I did. I'm waiting for the roofers to show up and put the actual skylights in.
So, one thing I learned after fighting to fit the first rafter in at full size- IT WON'T FIT FROM THE INSIDE!! I thought maybe I would be able to turn it sideways or nip the point of the top- but no! So, after checking with a building inspector, I cut 1-1/2" off at the bottom of the rafter (When in place, it actually ended up being more like 2.5" and it didn't matter which end I cut). This gave it the wiggle room I needed. I then put in a block at the bottom for it to rest on.

When putting the rafter in I tied a rope to the top of the rafter and put it through a small hole next to the existing rafter to pull it up (and hold it there while I screwed it into place). It worked pretty easily after I cut the bit off the bottom.

It would have gone into place full length if I had put it in from the outside but I would have had to cut all the deck boards out (they are re-decking the roof).

An interesting find when I exposed the rafters was, when they built the house, they used a 2x4 as the bottom plate. So you have a 2x6 cut at a 45 degree angle (which makes a resting edge of nearly 8.5") resting on 3.5". Strange! When I redo the flooring, I may put a block under the inside edge of the rafters because I see some cracking on some of the rafters where they (don't) rest on the 2x4". The photo is of my neighbor's house which actually has the 2x4 at the edge of the rafter point (even worse than mine which was roughly in the middle of the 2x6)

Also, in one pic, you can see an electric line running out from the between the roof deck boards- NOT MY HANDY WORK!. And its coming out! Also those J-boxes were mudded over- another no-no.

Thanks for all of your input.
And the moral of the story is if a 60 year "*old*" lady can do this alone- so could you! 
Still awaiting the inspection....



https://imgur.com/mCpeoXp




https://imgur.com/BquW3QY




https://imgur.com/SKqX55j


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## cda (Nov 21, 2020)

Aunty Lulu said:


> So, here is the framing that I did. I'm waiting for the roofers to show up and put the actual skylights in.
> So, one thing I learned after fighting to fit the first rafter in at full size- IT WON'T FIT FROM THE INSIDE!! I thought maybe I would be able to turn it sideways or nip the point of the top- but no! So, after checking with a building inspector, I cut 1-1/2" off at the bottom of the rafter (When in place, it actually ended up being more like 2.5" and it didn't matter which end I cut). This gave it the wiggle room I needed. I then put in a block at the bottom for it to rest on.
> 
> When putting the rafter in I tied a rope to the top of the rafter and put it through a small hole next to the existing rafter to pull it up (and hold it there while I screwed it into place). It worked pretty easily after I cut the bit off the bottom.
> ...



You go!!!!

Yep if they can cover it, people may not see it, till they need to open a wall.

I have been re dry walking my garage ceiling, never done dry wall before 

Had to add some wood, to screw the dry wall to,
Added a pull down stair , more added brace 

Yep learn as I go and YouTube


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## e hilton (Nov 21, 2020)

Feels good to know you did it yourself.


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## Aunty Lulu (Nov 21, 2020)

e hilton said:


> Feels good to know you did it yourself.


It feels like $1,000-$2,000- good! That is probably what I would have paid someone else to do it- or more. What I have found from scrabbling around on a ranch for 40+ years is there is always a way to get things done yourself. This job had me a bit intimidated but was I was very satisfied when it was finished.


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## Aunty Lulu (Nov 21, 2020)

cda said:


> You go!!!!
> 
> Yep if they can cover it, people may not see it, till they need to open a wall.
> 
> ...


Sounds good! I need to put an attic stair in at work. 
I LOVE YouTube!! Thanks to all of those people who take the time to make the videos!!!!


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## ADAguy (Nov 23, 2020)

Aunty Lulu said:


> Thanks- The rafters are indeed 16' from floor to ridge board (what I can measure with the room finished). The house is 115 years old so it must be working- back then they did what they did. The roof is 12:12 so maybe that helps. I did see on one place in the building code that one species is ok for that span but not the spacing. So, I will double the rafters and put in some beefy headers above and below the skylight to be safe. Thanks for your input.


 100 year old Rafters are most likely net as to dimension (old growth) and therefore can span a bit longer.


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