Ceiling joists are perpendicular to rafterslar

Second time I’ve seen these this week. But have never seen them before. I did some research and am wondering if anyone has any insight on this. This was an upstairs bedroom that had knee walls and 2 small sections of attic on either side. The home was built in the 40’s there is subfloor tying the joists together.

The ceiling joists are clearly visible in your second pic under those 2X4 perpendicular to rafters so for me its not a concern.

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Hey Marcel thanks. When you say 2x4 are you talking about the subflooring planks that are running parallel with the rafters? Would this tie everything together?

The ceiling joists (under the 2X4) are preventing the rafters from spreading, not the planks.

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Ah ok thank you

I’m not exactly certain what your question is…but in explaining…Carpenters will run the joists the shortest span possible, like over a one car garage, perpendicular to the rafters to meet the span rating of the joists. The short stubby joists are called lookouts and they help tie it together. In good construction a catwalk is installed on top to tie the lookouts to the joists to prevent spreading of the walls caused by outward thrust. Plank flooring (as you see here) can serve the same purpose if it extends to the lookouts. Depending on the time period of when the house was built (due to economic hard times) rafters was sometimes made with wood which was narrower (like a 2x4) instead of 2x6 or greater which we are accustomed to seeing now days and is sometimes a concern. I can’t tell from the picture which was used here.


When you have ceiling joists running perpendicular to the rafters, you typically need rafter ties, often installed 4 feet on center. I don’t see this in what you posted. It is possible the roof is supported by a structural beam instead of mere ridge board, then you may not need the rafter ties. Otherwise, the loads of the roof will push on the walls and can spread them apart.

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Can you explain how this happens with the ceiling joists running perpendicular to the rafters?

Looking at the picture, I see wood planks resting on 2X4 which are perpendicular to the rafters. Under those 2X4 at soffits area, I see ceiling joists which runs parallel to the rafters preventing them from spreading.
Doc1.pdf (33.7 KB)

Those (the ones you are pointing at with an arrow) are jack ceiling joists nailed to the perpendicular ceiling joist, the 2x4 you are referring to are the ceiling joists and they are at least 2x6 Per my post above, the rafter ties are missing.

This is not a gable end with flying rafters, what are you talking about? Either I’m seriously confused or I am about to learn something really cool and new. Please do explain your post.

I feel like I might be qualified to talk about this…for more info see… The Roof Framers Field Manual

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Basically I just want to make sure that no spreading will occur the way this is framed out. Generally when I see ceiling joists they run parallel with the rafters. But I found this article about IRC code and perpendicular ceiling joists. https://www.awc.org/pdf/education/mat/AWC-MAT108-Roof-071024.pdf
A structural ridge beam can be used, metal strapping, subflooring, or rafter ties. It pretty much sums up what you said, thanks for your help

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Understandable, but it was framed that way 80 years ago. Any signs of spreading or framing failure?

I don’t see anything wrong with the way that is framed. Obviously it has proven itself with the test of time.
That is the way it was done then and even today, in today’s standards a strap would be added on top of the ceiling joist, run flooring to grab those out lookers or add a rafter tie directly above the ceiling joist that are there.

What is missing in the OP’s picture is that there might be a wood lathe ceiling underneath that we don’t see and might be holding all together in some locations and the knee wall he mentioned is also holding up the rafters helping in a potential rafter spread that obviously has not happened.
Here is a detail from 2003.


Thanks Marcel. Yep it definitely did stand the test of time. I just was reading the same link that you posted those pictures from.

And still framed like that today with slight modifications to meet that code of late. :smiley: