I have a situation in a 25×40 SFD where the ceiling joists/ rafter ties are 2×4 dimensional DF. 16 o.c. spanning app. 12.5′ (25′ with a bearing wall down the center): single story, little to no storage in attic (20psf), 9′ p&l ceiling (to be removed). From my understanding this is overspanned (which would explain some sagging an plaster patches) and I would like to upsize them as part of a ‘remuddling’ project. Without rebuilding the roof, however, I see three options but would like to others ideas or feedback on these:
1) once ceiling finsh is removed sister in 2x6s on the top plates, I’m concerned however that the heel would need to be clipped excessively and compromise the strength of the bearing portion.
2) install a ledger on opposing top plates, and hang new CJs with hangers or pressure blocks, hanging down below the existing CJ (or pushing them up and creating some wall/ ceiling corner detail to hide the ledger)
3) as covered in a recent FHB issue, install some headers in wall pockets below the existing Cjs and then trim them out as a box-beam feature/ detail (this is likely the most problematic as they would need to be installed parallel to the long axis and there is some existing open spaces and cantilevered bay window to deal with).
Any a) feedback on these ideas or b) other ideas?
Thanks,
David
Edited 5/8/2009 9:30 am ET by peedee
Edited 5/8/2009 11:26 pm ET by peedee
Replies
I don't have your answer, but here is a bump and some feedback.
I would think sistering on is the solution, and clipping the top of the 2x6 wouln't be a big issue. If you are replacing ceiling with drywall, I think the weight will be reduced also.
Mike
Small wheel turn by the fire and rod, big wheel turn by the grace of god.
Thanks, I realize now that the OP is a bit long and hence likely deters some from reading and subsequently responding... but then again there's always hope :)
#1) Sistering 2x6's ok for limited attic storage (20#/sf) for you span of 12.5 LF. If you think that more attic storage would be ever be imposed/desirable, you might want to bump up the joist to 2x8's. Clipping no problem. Bearing/shear usually not of concern under normal circumstances.
#2) If I understand what you saying, I don't see the need if you do #1.
#3) Again. If I understand your problem (not there to see it) #1 should be adequate.
And as Ruffmike indicated, getting rid of the lath & plaster will help.
Thanks for looking these over giving feedback on the options, oops. I agree #1 is the easiest and most common, I was considering the alternatives in the event the clipping compromised the strength excessively.
David
Clipping the end of a joist won't affect the sag at mid span; all it will do is reduce the shear resistance at the point of support. In that a 2x4 has more than enough shear resistance, clipping the end of a 2x6 to 3½" deep shouldn't cause you any problems.
If you're worried about the joist splitting at the heel of the notch, you can band the joist to prevent that. Easiest way to do that would be with a steel-band packing strapper; you could probably borrow one from your lumberyard or (even easier) notch all the joists then bring them into the yard along with a six-pack of something frosty and ask the guys to strap them for you.
BTW, if there is any chance of the attic being used in any 'live' sense, you should go up to 2x8. A 2x6 floor joist shouldn't span more than 10' (and that's for SS; #1&2 is limited to 9'6").
Dinosaur
How now, Mighty Sauron, that thou art not broughtlow by this? For thine evil pales before that whichfoolish men call Justice....
Thanks Dino, those are some relevant and important thoughts and ideas for me to consider. I appreciate the input.
David