18.5" width opening to attic?

[slakwhere]

so i finally got the keys to the new house with the massive stand alone garage, and cut access to attic. the beams are 20" centers, making the opening 18" or so between. all the kits i saw at HomeDepot are 22.5" or 25".

do i need to remove a beam and frame in a 22" or 25" opening?

 

[Stuart in MN]

20 inches on center is an odd size - are all of them the same?

 

[slakwhere]

i didn't measure all of them, but yes they all seem to be pretty uniform. i'm 3 or 4 feet off the wall so it should be the general spacing.

 

[GeorgiaHybrid]

My attic trusses are spaced at 19.2 centers (5 spaces for 8'). I have been wondering the same thing but I will not cut a truss bottom chord so it looks like I will need to build a ladder from the storage level up the wall and go between two trusses. I hope the guy blowing the insulation isn't to hefty...

 

[Lawson4450]

well as long as you transfer the load by boxing out the area and giving it proper supports you can make it a little bigger just have to frame it out properly.

 

[slakwhere]

well as long as you transfer the load by boxing out the area and giving it proper supports you can make it a little bigger just have to frame it out properly.

yeah i'm leaning that way, just curious what "proper" is. i've framed in non-load bearing members but don't wanna cut this thing in half without a proper plan.

 

[CD1]

You should also build a temporary support wall to support the joist when you cut it, so the ceiling doesn't sag. After you've boxed in the area and tied into the joist you cut, you can then remove the support.

 

[Stuart in MN]

Are we talking about conventional rafters here, or manufactured trusses?

 

[GeorgiaHybrid]

Mine will not get cut, they are pre-man trusses. The bottom chord is a tension element with no good way to transfer the load to the two trusses on each side.

 

[ishiboo]

Mine will not get cut, they are pre-man trusses. The bottom chord is a tension element with no good way to transfer the load to the two trusses on each side.

Why not? In stick-built joists, the bottom chord is the tension element as well. Are there any attic/roof designs where the bottom chord, if structural is NOT in tension?

They're cut all the time, I just did my attic as I had ZERO access.

Bolt a 2x6 above and below to the joist you are cutting and each side around it, then cut flat 3" beyond where you want your opening.

Using the same size member as the chord (ie, if a 2x6 use a 2x6), nail or bolt TWO of the members together to the joists on each side. Using lag screws and washers, bolt the chord through these two members. As you said it is under tension so screws or nails are no good for that particular joint.

 

[kbs2244]

I would be more comfortable narrowing one of the stair “kits.”

 

[Falcon67]

Put some 2x6 angle bracing between the lower chord to be cut and the neighbor chords on both sides of the hole. I'd cut them so they'd bear on the framing surrounding the hole. That would help transfer some of the loads to the neighbor members and the framing of the opening. Should not really be an issue. Double headers on each side of the cut.

19.2 is a known spacing spec, just not used very much I think.