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Old 07-18-2014, 09:03 AM   #1
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Attic Access: Double Joists Needed?


I've seen this topic addressed elsewhere, but each situation seems to be unique, so please bear with me for asking a question that's already been discussed.

I'm trying to add a second access to the attic space above my garage, which already has pull-down stairs. (I want to install a light duty hoist in the attic, to avoid repeated trips up and down rickety pull-down stairs with armloads of said junk.) I feel sure that my attic space is intended to hold significant loads because the floor joists are 2x10 -- 16" on center. (In fact, I think this space is actually designed to be a finished bonus room -- which we may tackle one day, but for now, I just need the extra storage space.)

I want the new attic access hole to be 24" x 48", which will require cutting one joist, so that the new access will run parallel (in between) the remaining joists. My question is whether I need to double-up or "sister" the remaining joists to help support the load previously carried by the cut joist.

Obviously, I'll install proper headers, etc. But my question is simply whether the joists to which I'll attach the headers can stay as-is, or do they need to be doubled up?

I've attached a (not to scale) drawing, for reference. The blue lines represent the potential new joists, which I'm hoping to avoid. The attic space is quite large (roughly 24' by 20'), bisected in the middle by a beam, which is reinforced with a steel plate.

Thanks in advance for your help and advice.
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Old 07-19-2014, 06:52 AM   #2
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Attic Access: Double Joists Needed?


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i am no pro. but i think that would be ok.

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Old 07-19-2014, 06:58 AM   #3
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Attic Access: Double Joists Needed?


Yep---they should be sistered to properly support the new load----
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Old 07-19-2014, 08:11 AM   #4
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Attic Access: Double Joists Needed?


doubles on both sides of opening( sistered) and doubles for the headers you add in to form opening. four double 2x10 hangers for your header and 4 single hangers to catch the joists that you cut for the opening. get the sisters over to the beam to bear on and back to the wall opposite side- 1 1/2" minimum bearing requirement onto plates/beam etc...
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Old 07-21-2014, 11:15 AM   #5
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Attic Access: Double Joists Needed?


Thanks for the responses, guys. If I tweaked the design, so that the opening was only 24" x 24," would I still need to double up?

I'm looking at Building Code R502.10:

"Openings in floor framing shall be framed with a header and trimmer joists. When the header joist span does not exceed 4 feet the header joists may be a single member there same size as the floor joists. Single trimmer joists mar be used to carry a single header joist that is located within 3 feet of the trimmer joist bearing. When the header joist span exceeds 4 feet the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the floor framing into the header."

I'm willing to have a smaller opening, if it saves the trouble of doubling the joists.

Thanks, again, for your help.
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Old 07-21-2014, 11:48 AM   #6
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Attic Access: Double Joists Needed?


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Originally Posted by coleman1279 View Post
Thanks for the responses, guys. If I tweaked the design, so that the opening was only 24" x 24," would I still need to double up?

I'm looking at Building Code R502.10:

"Openings in floor framing shall be framed with a header and trimmer joists. When the header joist span does not exceed 4 feet the header joists may be a single member there same size as the floor joists. Single trimmer joists mar be used to carry a single header joist that is located within 3 feet of the trimmer joist bearing. When the header joist span exceeds 4 feet the trimmer joists and the header joist shall be doubled and of sufficient cross section to support the floor framing into the header."

I'm willing to have a smaller opening, if it saves the trouble of doubling the joists.

Thanks, again, for your help.
anytime you cut a joist for an opening the weight from the cut joist gets carried/transferred over to the joist members aside of cut joists via a header,hence the reason for doubles to catch the added weight, plus the door and stair weight with you and whom ever else decides to climb up and down them.
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Old 07-21-2014, 01:43 PM   #7
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Attic Access: Double Joists Needed?


Quote:
Originally Posted by hand drive View Post
anytime you cut a joist for an opening the weight from the cut joist gets carried/transferred over to the joist members aside of cut joists via a header,hence the reason for doubles to catch the added weight, plus the door and stair weight with you and whom ever else decides to climb up and down them.
That makes total sense to me, but I thought the code was saying that, as long as the opening is small enough (less than 48") and close enough to a load-bearing point (within 36"), then single joists are fine.

Not trying to argue -- just trying to understand! I appreciate all the help.
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Old 07-21-2014, 04:17 PM   #8
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Attic Access: Double Joists Needed?


just as a FYI since you mentioned codes in post #5


From the 2009 International Residential Code (your code may differ):

SECTION R807 ATTIC ACCESS

R807.1 Attic access.
Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or greater. The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members.

The rough-framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. When located in a wall, the opening shall be a minimum of 22 inches wide by 30 inches high. When the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics.

just some food for thought ......

Good luck!
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Old 07-21-2014, 07:15 PM   #9
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Attic Access: Double Joists Needed?


Thanks, GBrackins! That's great to know.

So... drumroll, please.... If I make the minimum size access hole (22" x 30"), would I need to double the joists, assuming that no header is more than 36" from the joist bearing point on the load bearing wall?

If I'm reading right this would satisfy both R807.1 and R501.10... right? Right? (fingers crossed)
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Old 07-21-2014, 09:12 PM   #10
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Attic Access: Double Joists Needed?


my understanding is you are correct. however most nail bangers will still double up on the framing. just a little more in materials and time, you have to remember the codes are bare bone minimums.

good luck!
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Old 07-22-2014, 09:31 AM   #11
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Attic Access: Double Joists Needed?


Got it, and understood about the "bare bones." I still may still double up the joists.

I really appreciate everyone's help.
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Old 07-22-2014, 09:13 PM   #12
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Attic Access: Double Joists Needed?


The other thing which every attic access needs is a bunch of nails and what not sticking out to bang your head on as you're trying to get up there. Seriously, make the hole as big as you can if you plan on going up there. If your joists are 16" oc, then you know 32 won't work, so you may as well go to 48, which you will reduce to 45 with the trimmers.

And locate this access where you will have plenty of headroom above it, and plenty of room for a staircase below.

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