# Sagging Joists & Strongback Question



## Yodaman (Mar 9, 2015)

1-2" sag over 12' is a lot. It may be split. If possible remove the bad joist and replace with the same size. Over sizing will force you to notch the strong back or the over size joist any way. If a sister approach is used jack up the sagger a little above level before you attach the sister. 
Regarding a strong back support, 12' is not a wide span, so one in the center will do. You should try to get the longest possible board in there. Anything you do will obviously help.


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## PSUlion01 (Jul 16, 2015)

Thanks. 2" is probably aggressive, but it's close to 1" I think. I can't say for certain as I haven't ripped the ceiling apart yet. I need a game plan to avoid dragging the project out (wife isn't going to be happy with a giant hole in the ceiling for more than a few days!) 

Good call on the strongbacks and using the larger joist. I didn't even think of that and would have realized it when doing the work. 

Assuming I need multiple boards for the strongbacks to span the 23', would I just want to overlap them as I run them across, I.e. First one from 0-8', second from 6'-14', etc.? Hope that makes sense?

Lastly, what should I use for the strongbacks? 2x4 laid flat with a 2x6 coming up, or something larger?

Thanks for the quick response. 


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## carpdad (Oct 11, 2010)

It may not be the framing. It could be the drywall, plaster, lathe, whatever that detached from the frame. You should inspect the roof as well for leaks and the condition of the insulation.


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## Yodaman (Mar 9, 2015)

I would use 2' for strong back overlap, 2 x 6 down flat and 2 x 8 for the vertical


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## PSUlion01 (Jul 16, 2015)

Not the drywall. I thought (hoped) it was just sagging drywall, as I've been fixing that on the walls in almost every room of the house. Drilled a hole under the sag with a spade bit and the joist was right under the drywall - no gap so it appears to be a framing issue. 


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## carpdad (Oct 11, 2010)

Reconsidering, if the joists are undersized, strongback will not work. You either have to add better joists or put a header there. Strongback will not hold up the joists unless the joists are not only self supporting but also will hold additional weight. Before you open the ceiling, get to the problem joist anyway you can and find out what happened to it.


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## PSUlion01 (Jul 16, 2015)

Thanks for the thoughts. Unfortunately there's no access to this area of the house, so the only way to see what's going on is to open the ceiling. Did this today as it's the only way I can move things forward.

Luckily I didn't see any signs of leaks or other things that might have caused the problem. All of the joists seem to have a 2x4 laid flat and running perpendicular, much like a strongback but without the vertical 2x attached. The joist in question seems to have sagged or warped, and pulled itself from the 2x4 strongback (if that's what this should be called). The other joists seem to be fine, except for one other a few feet away that seems to be starting to do the same thing. 

As of now the plan is to cut the sagging joist and either sister it or completely replace with a new 2x6. Then I'm thinking I'll try to screw that 2x4 pseudo-strongback into the joists just to keep it from pulling out again (unless this is ill-advised). 

As for the other joist that seems to have sagged a bit, I'm still not sure how I'd like to handle. I'd prefer not to rip more sheetrock down than necessary, so I'm hoping I can either screw a support of some sort or jack up the sagging area to correct it. 

Just curious as to why you said the strongbacks wouldn't work? I'm just looking to create a little more strength to keep a rogue joist from twisting or warping. Can you elaborate a bit on why you said it wouldn't work?

Attempting to attach a pic showing the problem joist. Thanks again for the help.











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## carpdad (Oct 11, 2010)

The strongback is not a header. It replaces blocking, more than holding the joists up so that they stay straight. I guess if you overlap them by 3-4 joists, more joists means more holding strength, but if you put heavier strongback, the added weight could become problem. It's not so simple as just adding more wood there. A header has load bearing supports at the ends. In this case the joists are bearing the load, and it becomes a guess how much they can bear. 
But it looks like other joists are fine, and just that one joist is the problem, although if one nail and 2x4 make the difference, the joists are undersized.
In the middle of the ceiling, cut a hole in the joist bay about 6'. Start with hand saw and watch out for any power lines, etc.
Cut out the 2x4 strongback over the work area and the problem joist. You can add one later. 
Support the joist with ply pad and 2x4 with slight pressure on the ceiling. Anchor the pad in the drywall and 2x4 supports with screws. The pad should help spread out the load and let you see if the drywall might go back without breaking. Cut 2 lines in mid joist about 1/2" apart and about 1/2 way up and knock out the cut. The joist should start to move up. Put more pressure on the 2x4 supports. If the joist doesn't move, cut the whole thing.
Slip in new joist. Get a lumber with slight crown and install crown up. It would be best if the joist sits on supporting wall, but you can use the old joist. Get the longest you can work with and don't patch with 8' ply or such.
Thinking about it, maybe something was hanging on that joist.


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## PSUlion01 (Jul 16, 2015)

carpdad:
Cool, thanks. All makes sense to me now. Putting in a header isn't an option now. The span is too wide for me to be able to do it myself, and I'd need to rip the whole ceiling down. I'm going to try and fix the problem area and if problems persist I'll likely have a pro come address things.

A few questions:
1) When cutting the joist, I assume I cut the notch from the underside and not the top of the joist. Can you confirm?

2) The drywall is already cracked for the majority of the 12' length. Assuming I can get the new joist in place without needing to remove all of the busted drywall, and the existing drywall snugs back up to the new joist, can I get away with keeping the cracked piece and patching it up? My concern is that it's cracked along the joist where it would nee to be screwed in. Seems like the structural integrity is already compromised and would need to be replaced. Thoughts?

3) Should the 2x6 joists be able to hold me (I weigh about 175) if I were to climb up into the ceiling? In addition to this framing work, I'm in need of new/more insulation and am looking to run some recessed lights in the rooms below me. It would be easy if I could work from above but I'm concerned about the load on the ceiling. I'm less concerned with the ceiling collapsing, but more worried that the joists deflect and crack more of the good drywall. 

Thanks again. Very helpful info here. 


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## BigJim (Sep 2, 2008)

If you can get into the attic in that area you can make a stiff back beam using plywood and 2xs. A 2X6 over that length will sag, but, screwing a 2X4 flat to the joists (after jacking the downward crown back up) plywood nailed and screwed to the 2X4, staggered, will hold the joists in place. What you are trying to achieve is build a truss beam of sort. You will have to support the ends of the truss beam on a wall to hold the pressure.

I have an entire ceiling supported this way with a beam similar to this.

If you were talking about removing all the ceiling joist, you don't want to do that without supporting the ridge of the house, those ceiling joists are keeping your outside walls from spreading and keeping the ridge from dropping. Trying to correct a mess like that is really hard.


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## PSUlion01 (Jul 16, 2015)

BigJim said:


> If you can get into the attic in that area you can make a stiff back beam using plywood and 2xs. A 2X6 over that length will sag, but, screwing a 2X4 flat to the joists (after jacking the downward crown back up) plywood nailed and screwed to the 2X4, staggered, will hold the joists in place. What you are trying to achieve is build a truss beam of sort. You will have to support the ends of the truss beam on a wall to hold the pressure.
> 
> I have an entire ceiling supported this way with a beam similar to this.
> 
> If you were talking about removing all the ceiling joist, you don't want to do that without supporting the ridge of the house, those ceiling joists are keeping your outside walls from spreading and keeping the ridge from dropping. Trying to correct a mess like that is really hard.


BigJim: 
Having a hard time picturing what you've described. Are you saying to run the 2x4 flat and on top of the joist (parallel over the 12' length), and then attaching the plywood vertically to the 2x4? Or are you saying to connect the ply to the rafters, thus connecting the joist to the rafter almost like a truss?

Or... are you describing a strongback like the one pictured, but running from wall to wall, perpendicular to the joists? I appear to have part of this going on now... there seems to be 2x4s running perpendicular, but there's no vertical member and the 2x4s are only 8' or so, overlapping by a few feet. The length of the room if running perpendicular to the joists is about 23', so getting one continuous piece of lumber from wall to wall isn't going to happen as a DIY (as mentioned in an earlier post).

As for removing all of the joists in order to replace -- no, definitely not going that route. I want to fix this one that's sagging bad, and possible correct another one a few feet over that seems to be showing similar issues (though not nearly as severe.


As an aside, I've noticed that despite the eaves of my house having the perforated vinyl, the soffits appear to be solid and fully enclosed. My guess is that when the previous owners had the siding done, no vents were cut into the soffit to allow for proper airflow for the ridge vent. Would the lack of circulation or excessive heat lead to the bowing/warping of the joists? I wasn't planning on such issues, but it seems like there should be vent holes cut into the soffits and if i'm up in the ceiling I may just try to do it.

Thanks!


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## hand drive (Apr 21, 2012)

PSUlion01 said:


> BigJim:
> Having a hard time picturing what you've described. Are you saying to run the 2x4 flat and on top of the joist (parallel over the 12' length), and then attaching the plywood vertically to the 2x4? Or are you saying to connect the ply to the rafters, thus connecting the joist to the rafter almost like a truss?
> 
> Or... are you describing a strongback like the one pictured, but running from wall to wall, perpendicular to the joists? I appear to have part of this going on now... there seems to be 2x4s running perpendicular, but there's no vertical member and the 2x4s are only 8' or so, overlapping by a few feet. The length of the room if running perpendicular to the joists is about 23', so getting one continuous piece of lumber from wall to wall isn't going to happen as a DIY (as mentioned in an earlier post).
> ...


personally I would get a 12" 14' LVL and rip it in half to 5.5" to sister fix the two problem joists. use the lvl as a sister to attach to problem joists after getting problem joists straight. make sure sister joists bears onto outer exterior/interior walls at least 1- 1/2" full bearing. do all work from within attic...


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## Yodaman (Mar 9, 2015)

PSUlion01 said:


> BigJim:
> 
> As an aside, I've noticed that despite the eaves of my house having the perforated vinyl, the soffits appear to be solid and fully enclosed. My guess is that when the previous owners had the siding done, no vents were cut into the soffit to allow for proper airflow for the ridge vent. Would the lack of circulation or excessive heat lead to the bowing/warping of the joists? I wasn't planning on such issues, but it seems like there should be vent holes cut into the soffits and if i'm up in the ceiling I may just try to do it.
> 
> Thanks!


Yes, sounds like somebody pulled a fast one on a unknowing homeowner. If the ridge vent has no intake it will pull the conditioned air from the house. Costing you extra to reheat or re-cool your living space. It also will pull in moisture vapors (and Radon) from the basement or crawlspace. Adding the soffit vents will keep the attic space cooler in the summer and dryer in the winter. Did the closed off soffit cause you the current problem? Hard to say, but it is causing other problems, you just weren't aware of them yet.

The ridge vents should equal or slightly exceed the amount of net free vent area of the ridge vent. Example if your ridge has a NFVA of 16 sq inches per foot, then a balanced soffit system should have at least 8 sq inches per side of roof to equal the 16.

The easiest thing to do now would be to cut a 1" wide slot from under neath the entire length of the overhang. The slot should be cut as close to fascia as possible. And of course you would have to remove the existing soffit first and re-install. If you try to do it from inside you will fill up the vents with saw dust. 

I wouldn't try to combine this project with your current, just put it on the list and know the sooner it gets done the sooner some of the things I spoke of will improve.


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## keymaster (Jul 28, 2015)

There are many excellent suggestions here. I'll add mine, which may be redundant, but might help with understanding.

1) If you can get into the attic space, this problem becomes much more easily solved. Most such spaces have an access panel somewhere, it might be tucked away in a hallway or walk-in closet. The 2x6s can support the average-sized person if you get some cut plywood panels and use them to distribute your weight, two panels can be "walked" around. 

2) If you can't access the ceiling, or if too much of the drywall needs repair anyway, make your own access in the area of the repair. Cut your opening in the area that looks the worst. Do this carefully, and make your cuts with a straight edge so that the patch can be easily applied. (A pre-drilled furring strip screwed in using drywall screws makes a cut guide perpendicular to joists.) Use a good drywall saw. Give yourself an opening that overlaps two to three joists in width and 4'-8' in length. Four feet long makes the drywall patch easier. 8' length will make getting new lumber into the opening easier. The width should be determined by the centers of the structure, as follows:

For the width, run the blade perpendicular to span, when it hits the joist skip over it, and run your blade _perpendicular _to the first cut, parallel to the outside edge of the joist. The outside edge of the joist is now your cut guide. If done correctly, you should have the 2 joists exposed to attach your patch when you are done. (After other repairs are complete, block between the joists with 1x mid-opening to stabilize the remaining cut edge of drywall, attach to drywall with drywall screws.) Turn off ceiling electrical before cuts.

3) If you can gain access, and are able to "walk" to the bad joist, remove the entire joist if possible and replace. (If others are suspect, remove them one at a time.) If you can get full bearing and replace the joist, use a 2x8, min. No reason to use undersized structure if you have the room, and it appears you do. 

4) If not, or if removal is too difficult, either sistering or a strongback (or beam) will work. Combining the solutions may add unnecessary weight. The "beam" may be nothing more than 2x material with straps, run perpendicular to structure, bearing on the top plates. (I found this drawing which is quite good. Notice that they get full bearing on structure, and also that they are gaining access from the exterior wall--which might be another possible approach.) NOTE: Block at ends to prevent tipping, or attach to studs.











When sistering, run your supports to structure (top of wall). If not possible, use smaller strongbacks which run perpendicular to structure, being aware of weight.

Ceiling drywall is a finish issue primarily for our purposes here, not a structural one, so you only are repairing it because the appearance is poor. If it is sagged, crumbled, cracked or doesn't attach well, it needs to be replaced. I would use a nice fresh sheet of drywall, but that's my preference, and it depends on things such as texture and finish. (If after getting this repair done, you need tips on finishing drywall, I'm sure there are many here who can help.) 

Use this as an opportunity to add insulation, when done.


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## BigJim (Sep 2, 2008)

PSUlion01, I was basically talking about what is in the illustration keymaster posted. 2X4 flat on top of joists (screwed tight) 3/4 plywood about 12 to 14 inches tall nailed and screwed to each side of the 2X4, stagger the joints of the plywood to break at 4 foot from each other. Nail 2X4 uprights at 16 inch centers especially on the break of each sheet of plywood. 

Envision a short wall about 12-14 inches tall with 3/4 plywood glued, nailed and screwed to each side.

I built a wall just like this over a garage years back to take the bounce out of the floor as they were adding a room over the garage. The only difference was I use full 1/2"X4X8 sheets glued with construction adhesive nailed and screwed and the wall ran from floor to rafters. The joints of the plywood joints must break at 4 foot, you don't want the seams to line up at the same place on each side of the 2X4 plate.


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## carpdad (Oct 11, 2010)

1. Yes, cut from under. You are making a curf cuts. Cut through the drywall and make sure there's no wire, etc, visually make sure from above.

2. Cracks may be more in the paint and skim coat. But if the drywall is damaged it is twice the work. Then go to the next bay and cut in the middle. Use 1x3 fur strip as a nailer to join the repair piece. It may be better to go to 2bays over if bigger area of sheetrock became mis-shaped. Add screws to the old part if nails or sheetrock has separated from the joists.

3. Going back to your first post, 2x6 spanning 12' is about the norm for unused ceiling. When you work on top, it may bounce or feel soft, but 2x6 is more than what you need. If you are adding on to the joists, support the ceiling from underneath. You don't want to add while flexing the joists with your weight.


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## PSUlion01 (Jul 16, 2015)

Thanks all... I've been away for a few days and have been meaning to follow-up on this thread and the status of the project. Here goes...



keymaster said:


> 2) If you can't access the ceiling, or if too much of the drywall needs repair anyway, make your own access in the area of the repair. Cut your opening in the area that looks the worst. Do this carefully, and make your cuts with a straight edge so that the patch can be easily applied. (A pre-drilled furring strip screwed in using drywall screws makes a cut guide perpendicular to joists.) Use a good drywall saw. Give yourself an opening that overlaps two to three joists in width and 4'-8' in length. Four feet long makes the drywall patch easier. 8' length will make getting new lumber into the opening easier. The width should be determined by the centers of the structure, as follows:
> 
> For the width, run the blade perpendicular to span, when it hits the joist skip over it, and run your blade _perpendicular _to the first cut, parallel to the outside edge of the joist. The outside edge of the joist is now your cut guide. If done correctly, you should have the 2 joists exposed to attach your patch when you are done. (After other repairs are complete, block between the joists with 1x mid-opening to stabilize the remaining cut edge of drywall, attach to drywall with drywall screws.) Turn off ceiling electrical before cuts.


This is helpful. I didn't have an access panel or door for the space above the ceiling, so I needed to cut an exploratory hole 2 joist bays wide and about 3' long. The tips for making clean, straight cuts on the drywall are helpful because I tend to be all over the place with the hand saw. I'll likely replace the full sheet of drywall, rather than try to salvage what's there. 

A question about removing the existing drywall though -- using your technique above (jumping the joist and using it as a cut guide), wouldn't I end up with an opening that's slightly larger than the 4' wide panel of sheetrock? I'd like to be able to remove a 4'x8' panel and simply replace, but due to the skim coat it's hard to find the seam on the existing damaged piece of drywall. Should I be cutting away the bad piece, or just breaking and pulling it down if the whole panel is to be replaced? I've been trying to cut the bad drywall with a blade right in the middle of the joist, and it's quite a chore, not to mention it only leaves me with 3/4" of joist for either panel to screw into. Sorry if I'm not describing this well, but I'm trying to understand what the 'proper' technique is to remove the full drywall panel and not end up with huge gaps after installing the new drywall panel. Also, any good tips for hanging the drywall without a lift? Temporary cleats on the ceiling of some sort?




keymaster said:


> 3) If you can gain access, and are able to "walk" to the bad joist, remove the entire joist if possible and replace. (If others are suspect, remove them one at a time.) If you can get full bearing and replace the joist, use a 2x8, min. No reason to use undersized structure if you have the room, and it appears you do.


So you'd suggesting replacing the bad joist using a ]2x8, rather than a 2x6, even if it means needing to cut and lose the existing strongback? Clearly the strongback in place isn't working, so I have no issues cutting and losing that, but by replacing with a 2x8, I won't be able to use any strongback on the replacement joist. I suppose it's not a concern, as the 2x8 likely negates the need to have the joist strongbacked, correct? Not that I'm looking to make this more of a project than necessary, but would there be a good reason to replace (or sister) all of the other joists with 2x8s, even if there are no signs of sagging or problems? 

The replacement joists will definitely span from wall to wall, overhanging by a few inches on each side, so it issues/concerns with them not being supported. If I do sister, rather than remove/replace, is there a preferred way to attach? Liquid nails + framing nails? Bolts?



keymaster said:


> Ceiling drywall is a finish issue primarily for our purposes here, not a structural one, so you only are repairing it because the appearance is poor. If it is sagged, crumbled, cracked or doesn't attach well, it needs to be replaced. I would use a nice fresh sheet of drywall, but that's my preference, and it depends on things such as texture and finish. (If after getting this repair done, you need tips on finishing drywall, I'm sure there are many here who can help.)
> 
> Use this as an opportunity to add insulation, when done.


Insulation will be added. I'll get those shields to keep it from by soffit vents that will someday be functional (!), and will probably get the blown insulation to cover the entire attic space. Since I don't have an access panel, i'm curious how best to insulate the opening in the ceiling that will eventually get closed back off? I'll probably leave a 4'x4' panel (the room is 12' wide, so i'll replace a full 4x8 sheet, leaving the 4x4 opening for access). Should i get batt insulation for this opening, or is there a better way to insulate the last area that will be closed off?

As for finishing the drywall, I still don't know how to proceed there. I don't have a popcorn ceiling or anything, but between the skim coat and decades of ceiling painting, is there a trick to getting the new panel to blend with the old? I may bit the bullet and just try to get a drywall guy to knock this portion out for me.

Thanks again for the support and advice...Appreciate the time you (and the others) have taken.


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## PSUlion01 (Jul 16, 2015)

carpdad said:


> 1. Yes, cut from under. You are making a curf cuts. Cut through the drywall and make sure there's no wire, etc, visually make sure from above.
> 
> 2. Cracks may be more in the paint and skim coat. But if the drywall is damaged it is twice the work. Then go to the next bay and cut in the middle. Use 1x3 fur strip as a nailer to join the repair piece. It may be better to go to 2bays over if bigger area of sheetrock became mis-shaped. Add screws to the old part if nails or sheetrock has separated from the joists.
> 
> 3. Going back to your first post, 2x6 spanning 12' is about the norm for unused ceiling. When you work on top, it may bounce or feel soft, but 2x6 is more than what you need. If you are adding on to the joists, support the ceiling from underneath. You don't want to add while flexing the joists with your weight.


carpdad,

Thanks for the reply. See my recent post for questions about the replacement joist sizing and drywall replacement. As I'd like to just replace the full sheet of drywall, any pointers on how to best remove the existing for a good, clean fit of a new 4x8 panel would be helpful.


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## Yodaman (Mar 9, 2015)

PSUlion01 said:


> carpdad,
> 
> Thanks for the reply. See my recent post for questions about the replacement joist sizing and drywall replacement. As I'd like to just replace the full sheet of drywall, any pointers on how to best remove the existing for a good, clean fit of a new 4x8 panel would be helpful.




Don't worry about cutting a perfect 4 x 8 hole out of the ceiling. Cutting the new drywall to fit is easier. But you should keep your cut out smaller than the 4 x 8. Cut down the inside of 2 joist using the joist as a guide. And then use 1 x 4 mat't or larger attached to the side of the joist to attach the drywall to. Be sure to keep your end cuts square on the cut out and the new pc. After the hole is cut out and you have measured it, cut your new pc a little smaller (maybe 1/4" in both directions). No fun holding a ceiling sheet over your head trying to fit it and fasten it. The tape and mud will easily cover the gaps. 

Good Luck


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## keymaster (Jul 28, 2015)

PSUlion01 said:


> This is helpful. ... A question about removing the existing drywall though -- using your technique above (jumping the joist and using it as a cut guide), wouldn't I end up with an opening that's slightly larger than the 4' wide panel of sheetrock?


Smaller than a full sheet is easy to fit and has straight edges, but is a lot lighter, which matters on the ceiling. If you use my technique, going two joists (one bay) in width is roughly 17-1/2," maybe 18" (assuming 16" spacing). Two joist bays in width (three joists) is 33-1/2" to 34"--_cutting outside the joist. _The length is under your control, and a good target is 4'--the width of a sheet. 



PSUlion01 said:


> I'd like to be able to remove a 4'x8' panel and simply replace, but due to the skim coat it's hard to find the seam on the existing damaged piece of drywall.
> 
> Should I be cutting away the bad piece, or just breaking and pulling it down if the whole panel is to be replaced? I've been trying to cut the bad drywall with a blade right in the middle of the joist, and it's quite a chore, not to mention it only leaves me with 3/4" of joist for either panel to screw into. Sorry if I'm not describing this well, but I'm trying to understand what the 'proper' technique is to remove the full drywall panel and not end up with huge gaps after installing the new drywall panel. Also, any good tips for hanging the drywall without a lift?


You will never find the edges of the drywall, you have to make your own cut as carefully as you can, use a square if possible to keep it from getting skewed, and then patch. The only tip I have on not using a lift is have a helper--or two--and work with about a third of a sheet, not a full sheet. The width of a sheet is 4 ft. Make that the length of your cut, plus an 1/8". The width of the patch is determined by the number of bays you cut, so for example, you might cut two bays, you take which means a 33-1/2" piece from the end of a sheet of drywall. A patch of 33-1/2" x 48." Don't just break off the drywall, cut yourself a precise opening or you will have a nightmare of a time patching it. 



PSUlion01 said:


> So you'd suggesting replacing the bad joist using a ]2x8, rather than a 2x6, even if it means needing to cut and lose the existing strongback? Clearly the strongback in place isn't working, so I have no issues cutting and losing that, but by replacing with a 2x8, I won't be able to use any strongback on the replacement joist. I suppose it's not a concern, as the 2x8 likely negates the need to have the joist strongbacked, correct? Not that I'm looking to make this more of a project than necessary, but would there be a good reason to replace (or sister) all of the other joists with 2x8s, even if there are no signs of sagging or problems?


I was disregarding the existing flat laid 2x as I felt it was not doing anything useful. If you follow my instructions (or others here), regardless of which approach you take you won't need it. A strongback is really a beam and it could be more difficult to install properly than replacing the joist(s) near the problem area. I'm not able to see it, so I can't advise about which approach is best. If you use 2x8, attached properly, I can assure you those 2x8s won't sag. _That doesn't mean other joists can't, however. _A 2x8 is a per joist solution, a beam is an entire ceiling span solution. (Needless to say, it will likely require full access to the attic space to install.) I would probably replace any that show signs of sagging, several either side of the sagging joist, with 2x8s, and let it go at that. Using 2x8s won't prevent other solutions later. Sistered 2x8s could be used to support a beam--or all remaining joists could be replaced.

Note: I would install an access panel (elsewhere, in a hallway) for future maintenance, if needed. 

I was trying to find where the span was mentioned and I can't find it. if the span is 12', then 2x6 are almost certainly undersized, as they max out around 9'-10,' depending on spacing and species. You don't want to be on the end of the span of a particular size of lumber. Depending on the span, replacement, or sistering is recommended if undersized.

*EDIT: *Okay, 12' span. This is undersized. You may very well have problem with other joists sagging. Either a beam is needed, or sistering/replacement of all joists. In areas where you have to refinish, replacement; in areas where you don't, I would sister the joist. 




PSUlion01 said:


> The replacement joists will definitely span from wall to wall, overhanging by a few inches on each side, so it issues/concerns with them not being supported. If I do sister, rather than remove/replace, is there a preferred way to attach? Liquid nails + framing nails? Bolts


If the replacement joist spans, that should be all you need. Sistering can't provide additional structural benefit here. (If you are talking about all the joists, and not just the repaired area, then sistering makes more sense.) I like the 2x8 simply because we know the 2x6 failed--for whatever reason. Maybe it's due to venting, or maybe undersized. 

(If you still want to sister them, I would toenail to the plates, both sides, and screw into the face, both sides. Attaching together is to stabilize and make them act as one. Screws do an excellent job. )



PSUlion01 said:


> Insulation will be added. I'll get those shields to keep it from by soffit vents that will someday be functional (!), and will probably get the blown insulation to cover the entire attic space. Since I don't have an access panel, i'm curious how best to insulate the opening in the ceiling that will eventually get closed back off? I'll probably leave a 4'x4' panel (the room is 12' wide, so i'll replace a full 4x8 sheet, leaving the 4x4 opening for access). Should i get batt insulation for this opening, or is there a better way to insulate the last area that will be closed off?
> 
> As for finishing the drywall, I still don't know how to proceed there. I don't have a popcorn ceiling or anything, but between the skim coat and decades of ceiling painting, is there a trick to getting the new panel to blend with the old? I may bit the bullet and just try to get a drywall guy to knock this portion out for me.


If you are going to replace entire panels, you will need two helpers to hold it up while another is doing the attachment. I would create a square or rect. access panel in a remote area--keep it small but to code--and then insulate the top with rigid insulation. 

We can treat finishing as a separate problem. Finishing drywall is something about which few can agree. Asking about it is opening an can of worms. Let's cross that bridge when we get to it.


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## keymaster (Jul 28, 2015)

I'm not able to edit that post, but I realized only after posting that the span was 12,' which does change my advice. Sistering 2x8s or a beam makes the most sense, as I now know that _all _ceiling joists are undersized, and your problem could repeat itself with other joists. Replacement only makes sense in areas where the drywall is needing replacement as well. (Sorry if that resulted in some seemingly contradictory advice.)


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## PSUlion01 (Jul 16, 2015)

keymaster said:


> I'm not able to edit that post, but I realized only after posting that the span was 12,' which does change my advice. Sistering 2x8s or a beam makes the most sense, as I now know that _all _ceiling joists are undersized, and your problem could repeat itself with other joists. Replacement only makes sense in areas where the drywall is needing replacement as well. (Sorry if that resulted in some seemingly contradictory advice.)


Thanks...A few follow-up questions, as I may begin working on this tomorrow afternoon.

1) Just for my reference, can you point me to a good source for joist span tables? I'm not questioning that the 2x6 joists aren't sufficient (as illustrated by my disaster of a ceiling), but most of the tables I see online are saying the max span for a 2x6 that is 16"OC is around 16 feet. You mentioned 9-10', so which is it? This leads me to my next question...

2) Is there any other possible approach for the joists not currently showing any signs of problems? I'll likely be doing most of this myself, so the task of getting 15-20 16-foot 2x8s, getting them up into the ceiling and installed isn't something I'm completely thrilled about. If it's the best or only way then I'll do it, but would I be able to sister a few 2x8s, say every 4 joists or so, and then strongback the 2x8s and attach the 2x6 joists (that were not sistered) to the strongback with a small truss or a steel strap or hurricane tie? \

I don't plan on using the space for storage, so really I just want to keep the joists from sagging more and leading to this project all over again. My house is from the mid-60s, so part of me wonders if i'll have problems with the other joists if they haven't shown signs of problems by now. Is it possible that the two joists that sagged were crowning to being with, which just amplified the problem? I know it's hard to say for certain, but I appreciate the opinions here. I'm not one to take shortcuts, but I also don't want to overdo this if truly not necessary.

Thanks again!


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## carpdad (Oct 11, 2010)

I'm not very good with reading the span charts, but the span charts are easy to get. If not this forum, search 2x6 ceiling joist span. Your case will include:
1. dead load - construction material only. Look for number 10. No live load.
2. 2x6 grade #2 douglas fir which is most common and applicable in general.
3. joist spacing - 16" o.c.

Personal experience: I used 2x6 to span 12.5', 16" oc ceiling, crawl space attic. Only insulation and 1/2" drywall. Passed all plan inspection. 10 years before selling. No sag. This is in NJ.

I think you want to make it bullet proof, which I think is a wrong approach based on one joist. I think the best way to reinforce other joists is what's been mentioned already. Ply glued and nailed to the joists. 12" rips (4 sheets from a ply) of 3/4 cdx, construction glue and 8d nails 3 each row and 12" apart. Center the ply on the joist and use 1/8" paint stick for a spacer from the drywall. Remove spacer. Support the joist from under while youre on it.


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## PSUlion01 (Jul 16, 2015)

carpdad said:


> I'm not very good with reading the span charts, but the span charts are easy to get. If not this forum, search 2x6 ceiling joist span. Your case will include:
> 1. dead load - construction material only. Look for number 10. No live load.
> 2. 2x6 grade #2 douglas fir which is most common and applicable in general.
> 3. joist spacing - 16" o.c.
> ...


Whereabouts in NJ? I'm up north (Wayne). 

I hear what you're saying. One (maybe two) problem joists and i'm talking about re-working the entire ceiling. As stated earlier, the only reason i'm looking to possible address the whole ceiling is because I don't want to be repeating this exercise in a few years. However, we're considering either having a room built above this space a few years from now, or having the ceilings vaulted (it would all be done by professional contractors as part of a larger reno at the house, so my joist work wouldn't be used to support the structure). All the more reason that I don't want to go too crazy, as this may only be needed for a few years. Then again, maybe that work never happens, so I don't want to take too big a shortcut.

Just so I'm clear, is the suggestion to do the following:
1) Replace the sagging joists with 2x6s, to be consistent with the rest of the ceiling.
2) Sister all of the joists with 3/4" ply, cut to 12" wide (high)? A few questions here:
- Should the ply be sistered on each side of the joist? There will be a seam since I'd need an 8' and 4' piece to make the 12' span, so do I need to sister a 4' and 8' piece on the opposing side of the 2x6 joist?
- Could I go smaller than 12", possibly even down to 6" in height?
- Using this approach, the ply wouldn't extend over the wall plate, correct?

Thanks!


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## Yodaman (Mar 9, 2015)

Sistering 12" ply to the joist is a mistake. Will make it difficult to move around anytime after. If it's needed use another 2 x 6 full length. Or change them all to 2 x 8. Sometimes you just get a bad board! Replace it and get on with your life


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## PSUlion01 (Jul 16, 2015)

Yodaman said:


> Sistering 12" ply to the joist is a mistake. Will make it difficult to move around anytime after. If it's needed use another 2 x 6 full length. Or change them all to 2 x 8. Sometimes you just get a bad board! Replace it and get on with your life


Thanks, and I agree, time to get on with things. Appreciate the thoughts.


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## hand drive (Apr 21, 2012)

PSUlion01 said:


> Whereabouts in NJ? I'm up north (Wayne).
> 
> I hear what you're saying. One (maybe two) problem joists and i'm talking about re-working the entire ceiling. As stated earlier, the only reason i'm looking to possible address the whole ceiling is because I don't want to be repeating this exercise in a few years. However, we're considering either having a room built above this space a few years from now, or having the ceilings vaulted (it would all be done by professional contractors as part of a larger reno at the house, so my joist work wouldn't be used to support the structure). All the more reason that I don't want to go too crazy, as this may only be needed for a few years. Then again, maybe that work never happens, so I don't want to take too big a shortcut.
> 
> ...


with all that info it would suffice to just add a 2x6 sister to the problem joists. jack up the problem joist to straight and then sister on the 2x6 nailing/screwing double intervals @ every 16" along the span. just remember to set the sister to the outer wall plates at least an 1 1/2" . if you have wires in the way you can make small notches in the joist but not to big as to compromise the structural integrity.


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## Gary in WA (Mar 11, 2009)

You are under the IBC, and IRC; http://www.cmdgroup.com/building-codes/new-jersey/

Ceiling joist span tables for a 5#psf load is 16'6", for a 10#psf load is 12'8", they are not over-spanned if Doug-Fir #2; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_par027.htm?bu2=undefined


Just sister the bad apple or run a couple of 1x4 to the rafters above (near the peak and inline on same set) to carry them with a new 2x4 flat on each side of the cut one (to ease lifting back on plane) crossing two cjs on either side for added support. 
Make the access hole to minimum code and close to bearing wall with single member framing, no hangers required; http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_par034.htm?bu2=undefined

Trim it out with some painted door case, both horizontal and vertical to rest the drywall lid you removed and new foamboard insulation with drywall sandwich for ignition barrier on the lid.http://publicecodes.cyberregs.com/icod/irc/2009/icod_irc_2009_8_sec007.htm

Gary


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## keymaster (Jul 28, 2015)

PSUlion01 said:


> Just for my reference, can you point me to a good source for joist span tables? I'm not questioning that the 2x6 joists aren't sufficient (as illustrated by my disaster of a ceiling), but most of the tables I see online are saying the max span for a 2x6 that is 16"OC is around 16 feet.


The span depends on spacing, loads, deflection, species and lumber grade. I don't know what they used, so I made conservative assumptions, an attic designed for limited storage. Better grade Doug fir should have been plenty for a 12' span, assuming 5PSF dead/10PSF live, an attic with no storage. My approach was based on what you said: There appeared to be sag, a 2x6 support added at some point to support the joists, concerns about lack of soffit venting, and for me, unknown construction quality.

(The 9'-10'? No idea. Possibly thinking of 2x4 ceiling spans.)

Given the age of the building, and if it is just one joist that is sagging, that conservative approach looks unnecessary.

A resource you can look at is the Simplified Span Tables for Light Construction. American Wood Council is another, but more complicated. 



PSUlion01 said:


> 2) Is there any other possible approach for the joists not currently showing any signs of problems? I'll likely be doing most of this myself, so the task of getting 15-20 16-foot 2x8s, getting them up into the ceiling and installed isn't something I'm completely thrilled about. If it's the best or only way then I'll do it, but would I be able to sister a few 2x8s, say every 4 joists or so, and then strongback the 2x8s and attach the 2x6 joists (that were not sistered) to the strongback with a small truss or a steel strap or hurricane tie?
> 
> My house is from the mid-60s, so part of me wonders if i'll have problems with the other joists if they haven't shown signs of problems by now.


If you haven't had problems by now, for 50 year-old home, that one joist may be your only problem. (I should have asked the age of the home before this got started.) 

If the other joists don't show a problem, _don't do anything_. (Install an access panel in the hall.) You could just replace the sagged joist. I was originally going to suggest an alternative: sistering every third, or fourth. 

That last description of the strongback sounds great, basically my suggestion for a beam that doesn't span the entire ceiling. 2x8s, with a small header riding on them and connected to the ceiling joists with hurricane straps. Still, that may be much more than is warranted if no other joists appear affected.


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