good title huh?
i need to make an access to my attic (which is curiously absent). can i just cut a 3′ section out of one of the joists, and “head them off” with doubled up 2x material and joist hangers? when i cut, will there be any sort of deflection or “spring” that i need to counter prior to cutting? these are not engineered trusses, but conventional framed roof joists and rafters. they are 16″ o.c. 2x10s and the cut will be close to, but not on the center of the span (20′) which consists of “lapped” 2x material.
thanks everyone!
Replies
No, not usually. When you header something off the existing member on either side of the hole most often needs to be doubled for their full length. Some of this depends on other factors that we can't see from here - span, loads, etc.
>> they are 16" o.c. 2x10s and the cut will be close to, but not on the center of the span (20') which consists of "lapped" 2x material. << Lapped??? sounds like the span isn't really the full 20'.
Edited 1/20/2008 1:49 pm ET by Matt
That is true but as I understand this, he has a 2x10 spanning ten feet for the ceiling joists. That is already more meat than he needs to support a SR ceiling. he does say it spans 20', but since they are lapped, i have to assume they lap on a wall and in reality only span ten feet. The use of the word SPAN is one of the most oft misused here IMO.Admittedly I rely on assumptions and the description given to say no need to double in this case so I could be 100% wrong
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
I hate to think it, but from reading it carefully, it sounds like 2x10s were lapped and nailed together to span 20' - and he's looking to cut near the center of that span. I think that's why they're 16" O.C.
If the attic access is missing like he says in the op, then how does he know what's up there?"Put your creed in your deed." Emerson
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Cut a hole in the SR and pop your head up there, is my guess. If it's only needed for access to run wires or whatever, i'd just skinny up there between the joists and use an access hatch. If the rafter situation is anything like i'm imagining, i can't see storing much up there to require a stairway. Hopefully Piffin's correct and i'm wrong,, though.
LOL,
Damn perceptive!
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
"I think that's why they're 16" O.C."One would not have anything to do with the other. we typically stick frame at 16" oc but most trusses design out at 24" oc
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
???They'd be placed on closer centers if they were over-spanned, was my thinking.
or somebody said, hey, we've got a bunch of these here 2x10s, let's use them and then later we can put the pot farm up in the attic without making the ceiling sag;)I see where you were coming from though now.Isn't it fun speculating without the help of the OP?
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
He's probably a church-goer.You'll have to change your tagline to "The Church of Breaktime" for all of us Sabbatical sinners.
your assumptions are right on...as usual piffin. thanks
the total span front to back is about 21', so they're (joists) about 11' each, lapped by a foot over a wall.
are you suggesting that i need to double up from eave to eave on the outside members?
so the total LENGTH is 21' but the span is the distance they are unsupported from wall to wall, about 10-11 feet. A 2x6 @ 16" oc can handle that for ceiling only loading. if these are 2x10s at that layout, just cut one and header it off to transfer loads to the adjacent ones on either side.any plumber knows how...LOL
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
had another look,....it at first appeared that in some places, the rafters or the ridge beam were held up by some of the interior walls, but it turns out those are only short 2x4's that tie the walls into the roof, but i doubt that they have any structural use (as far as the roof goes), there's only about 4 in the whole attic. may i assume that since there is no roof load on interior walls, that the joists are indeed only holding up sheet rock and therefore i can apply what you wrote? the rafters btw, are 2x10 tied into ridge by joist hangers, and the ridge beam is a doubled 2x12.to be clear, the walls hold up the lapped joists, but they don't really have connection to roof, rafters, or ridge.thanks for everything, johnps, so i can chop right in the middle of the ridge to run my soil stack? (just kidding, plumber joke)
Edited 1/20/2008 5:52 pm ET by merlvern
Boy, someone must have been getting a kickback on the lumber for that one.
If your view never changes you're following the wrong leader
is there another option than doubling up the outside members? i literally cannot get out to the eavesthanks for the help
If the unsupported span is only ~10' and the joists are 2x10 they probably don't need to be doubled.
Seems odd that they would use 2x10s @ 16" OC for a 10' span with no other load but ceiling sheetrock(?) and insulation, but whatever...
BTW is there a beam or some other support that goes down to the foundation under this center wall?
stair wall on top of large doubled 2x10 in first floor ceiling, and a large tripled beam in the basement
probably OK based on the details given
Welcome to the
Taunton University of Knowledge FHB Campus at Breaktime.
where ...
Excellence is its own reward!
Are these lapped joists sitting atop a wall?
J. D. Reynolds
Home Improvements
thanks for all the responses...they are lapped over a wall, sorry for not including that.
the reason i can't just shimmy up thru 1 bay is that the pitch of the roof above is very shallow, allowing only about 22" of space in the attic......the only way i can get my 6 foot 220lb carcass up there is with more space....i need to adjust some wiring etc.
why not just get someone smaller, who can fit up there, to do the wiring? I think it would be a lot less hassle.Live by the sword, die by the sword....choose your sword wisely.
cause then i couldn't call myself a "do it yourself-er"....:)just kidding, i also want to wrap hvac, other wiring, bathroom vent, etc. gets expensive hiring folks, know what i mean.john
After you spend a few hours worming your 6' 220# body over the joists under 2" pitch rafters you will be begging to spend the money you saved as DIY.
There are only two instances where being a short as i am has been useful: attics and crawlspaces.
wife already spent it! no such luck :)
1 bay is that the pitch of the roof above is very shallow, allowing only about 22" of space in the attic
I'm going to guess some things here.
First off, that this is not "original" space, that this is converted space (converted attic or n.5 story). Which would explain things like tiny spaces with no access, and lapped joists (they were probably installed from below and set on the new partition).
I'm going to assume that Murphy insisted that the joists run perpendicular to the long 22" tall dimension, insuring that you need to be a contortionist to make the right-angle bend up in there (since Murphy will insist that you wil absolutely positively after all the stores are closed just before a holiday have to get to just beyond your reach).
See, if the joists were perpendicular to the rafters, you could probably get by with a 14.5 x 48 opening, so you could "roll up" on the joists into the 22" high area.
Stinkin' Murphy.
What might suit better would be 2-3 14.5 x 18 acccesses, each giving a different "reach" into this tiny space. Occupational hazard of my occupation not being around (sorry Bubba)
You (almost) always run the joists parallel to the rafters, so the joists can counter the thrust of the rafters. Otherwise the roof would fall flat, especially a low-pitch roof like this one.Eleven-foot rafters were used because they're easier to lift than 22-foot ones.
If your view never changes you're following the wrong leader
You (almost) always run the joists parallel to the rafters
Well, I was making allowances for some of the daffier things I've seen done. Running joists wrong-ways being one of those. If these did, then a long-skinny access would let a six-and-a-half foot person get into that 22" space, sideways like. Sure, they'd only be able to go forward and back, and it's drop out the attice to turn around. But, Murphy will have this one not allow that, sure as shootin'.
Otherwise the roof would fall flat, especially a low-pitch roof like this one.
Well, yeah, except I'm still guessing this is "found" space and what are now ceiling joists are occupying what had been collar tie locations, so the rafters may run past the top plates of this room.
Eleven-foot rafters were used because they're easier to lift than 22-foot ones.
Especially when they really need to be 21±' per the OP <G> And, those 22-footers are pain to get up the stairs <g>.Occupational hazard of my occupation not being around (sorry Bubba)
ding ding! you win the prize.converted single story cape with kind of a weird mansard like second story with low pitch roof.....we like the yard :)
2x10 ceiling joist are plenty strong enough to cut one and header would be better to do close to the wall and not the center. but if this is just attic space the reason they are 2x10 is not for strength but insulation space. you can get R33 in a 2x10 space and still be able to put plywood down to walk on or for storage.
If you wanted to add a 3rd floor and you were going to header off 3 or 4 joist to install a stair then yes you would need doubled joists (if not 2 LVLS) but that is not the case here. Also you only need to double the span that carries the load of the header so even if these where 22 foot joists if there is a load wall half way you only need to double from the load wall to the next load wall (the outside wall in this case) but lets say it in a hallway or closet you need double from load point to load point.
Many ceilings in older homes some with spans of 15 ft. have only 2x6 ceiling joists with a 2x4 nailed across on the flat as a strong back. and they support plaster ceilings much heavier then drywall. I have even seen 2x4 ceilings on some bungalows with small rooms (short span).
now I would not put much up in those attics but it is not a floor joist it is just there to support the a ceiling.
can't even get myself up there,...22" clearance, no worries about "storage" :)
thanks
You need to understand that the dynamics are different between a joist and a stud, when it comes to cutting an opening. A stud is under pretty much pure compression, with negligible lateral force. So the conventional door/window header scheme works to transfer the force to adjacent jack studs.
A joist is under tension and lateral force. Using standard studwall header techniques will do little to transfer the forces to other members.
To transfer the lateral force you can run a piece of 2x10 header-like between the adjacent joists. Use hangers to hold this new piece and then a hanger on it to support the end of the cut joist. If you really have 2x10s and are near the end of the span (assuming a load-bearing wall where the joists lap) there should be no need to double-up the adjacent joists, but there would be if you were cutting near the center of the span or had shallower joists.
To transfer the tension force you can nail a piece of 2x8 or 2x10 flat across the joist and it's two neighbors, a few inches from the cut point. Nail the heck out of it -- 4-5 16d or 20d into each joist.
i suppose, intuitively i figured there would be tension, that why i asked about "spring"thanks dan
In practice there's not likely to be much, but better safe than sorry.
If your view never changes you're following the wrong leader
""when i cut, will there be any sort of deflection or "spring" that i need to counter prior to cutting?""
Potentially yes, .
If you can skinny up far enough to place a 2 x on the flat across the joist outside of the area you want to cut and have it span across the adjacent joists it would be best . Screw it to the joists from above , if not all 3 then at least the one you want to cut .
That will hold things in place until you header things off and refastened the way you want.
Piffin and Dan have the rest covered.
yup, thanks,i appreciate the help