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How much a ceiling can you cut to install openings

How much a ceiling can you cut to install openings

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  #1  
Old 09-10-17, 03:47 PM
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How much a ceiling can you cut to install openings

I have a 2 story frame house. The roof has two peaks at different levels. I have two opening in the back half. One is an entrance to attic (36W X 24L) that I have to use a ladder to get into attic. The other is a whole house fan (34W X 34L). It has been this way for over 20 some thing years. The installer of the whole house fan had boxed the beams in the ceiling that he had cut like the ones the builder did around the attic opening that he did. MY question is now I would like to take out the whole house fan. The installer would like to cut one more ceiling beam to install a large attic folding stair. What I mean by boxed in is a support from ceiling beam to each other that is cut .The question is does it matter if 1 more ceiling beam is cut as long as it is boxed in (supported to all the ones next to it.
PS: I have included pictures of attic.Sorry but there is a lot stuff there.
 
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Old 09-10-17, 04:16 PM
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Your pictures dont show much of what we would need to see... all the ceiling joists. Generally, when 1 joist is cut and a section removed a single member can head off the cut joist on both ends of the opening and transfer that load to the single uncut joist on either side.

however when 2 joists are cut, they must be headed off with a double member, and the joists on either side must be doubled and must continuously span between 2 load bearing points. With 3 it gets a little sketchy and you should usually seek the advice of a structural engineer who will calculate the area, the load, and determine if a triple is needed or a microlam or?

In short, some structural questions can't be answered on the internet because there are too many variables, we can't see everything, whereas someone who is there in person can.

But I will say that if the hallway walls left and right of your whole house fan picture are load bearing, you should have no problem making the changes needed to make the opening longer.
 
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Old 09-10-17, 04:23 PM
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The installer would like to cut one more ceiling beam to install a large attic folding stair
Attic stairs are installed parallel to the roof trusses, it appears your attempting to install perpendicular. That is going to be tough!
 
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Old 09-10-17, 04:32 PM
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Attic stairs can be installed in either direction as long as the framing is done correctly.
 
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Old 09-11-17, 04:21 AM
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Instructions from my recent installation.

A Preferred, If the chosen location is parallel to the ceiling joists, mark the
length of the opening on the top surface of the joist as shown on Figure 8.

B Non Preferred, If the chosen location is perpendicular to the ceiling joists, mark
the width of the opening on the top surface of the joist as shown on Figure 9.
 
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