I have been on the site for some time gathering a lot of good information, but now I'm in need of a little advise so I registered. A little history on the garage and it's ridge line that's dipped about 2 inches. I am not sure how long the ridge has been sagging. I added insulation and drywall last to the ceiling and just noticed this year my ridge line has a sag in it. May have been there when I moved in a couple years ago, not sure. The trusses are 24 center on center. I have no knowledge about roofs. Plan is to jack up the middle 7 trusses out of 11 with Jack's and 2 2x4s screwed together because I have a bunch for free. I plan on using 2 cable binders towards the center some where to pull walls in and just leave them there. I understand all this take time in slow increments. Is that the right way to do it? Trying to do it cheap as possible. So by care of roof is perfect just don't want it to get worse. What do I need to do once it's straight again to prevent in from sagging again and hold the weight of insulation and drywall?
Sagging ridge line
- Thread starter btk
- Start date
wrenchguy
Well-known member
with that shallow pitch and home made trusses i believe u'll probably keep it from getting any worst. jack it up and put more cable binders into motion over a period of a month should do it. the walls spreading i believe is the biggest issue. as far as keeping it there think of running cables top plate thru opposite top plate with turnbuckle to draw up tight. when its good, plan on padding the bottom of the joist to be able keep cables in place, then insulate and osb.
LX-Markham
Well-known member
thought this was going to be another truck vs real truck debate.
Very odd for trusses to deflect that much. Where are you located? Lots of snow?
I would monitor it instead of trying to take the "sag" out of it.
Very odd for trusses to deflect that much. Where are you located? Lots of snow?
I would monitor it instead of trying to take the "sag" out of it.
matt_i
Well-known member
I would inspect every joint closely to see if anything is pulling apart. If so then I believe you have a problem that you could correct.
Its possible they were not all made to exactly the same dimensions and the "sag" is just manufacturing variation....and that's not something as easily repaired.
Its possible they were not all made to exactly the same dimensions and the "sag" is just manufacturing variation....and that's not something as easily repaired.
I will post pictures of the brackets I'm making for the cables and turn buckles once I finish them. I only planed on 2 1/4" cables running across is that enough? Can I add any wood that would help add strenth. Thought about sistering 2x6 on the bottom of the trusses? Not sure it would do anything. Im located in southwest kansas. Id rather get it fixed and my Insulation back up as soon as possible instead of monitoring it.
Bretny
Well-known member
My father had something like this happen in his garage. Walls bowing out to the point that framing started to fall appart. He took two bessey large bar clamps put them over the wall on the inside and used a come along to pull it back. Then added more horizontal collar ties.
You may also look into the holes in the tie plates to see if there ripping the wood. Plywood, screws and glue might be better if they are. I wouldnt use 1/4in cable. Thats far to thin. U wouldnt want to be in that garage if one broke.
How wide are the trusses?
I would avoid adding a post. My garage has one and i hate it.
You may also look into the holes in the tie plates to see if there ripping the wood. Plywood, screws and glue might be better if they are. I wouldnt use 1/4in cable. Thats far to thin. U wouldnt want to be in that garage if one broke.
How wide are the trusses?
I would avoid adding a post. My garage has one and i hate it.
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wrenchguy
Well-known member
put a cable next to every joist. probably wood stretching on all nails with snow loads, thats a shallow pitch thats not offering much strength, as in a steeper 1. i wouldn't add wood, cables r stronger. u should've left this job 4 warmer weather if needing heat that bad. that sag been there awhile. whats break strength of 1/4" cable?
matt_i
Well-known member
I question the logic of pulling the walls together on a trussed roof. For 2 reasons.
1. Unless there's a noted gap to close somewhere, likely resulting in nails elongating in the steel plates, the cable cannot compete with the compressive strength of the timber.
2. This is 100% reliant on the fastener(s) between the top plate and the bottom chord being able to transfer the cable load to the bottom chord. A lot of times its traditionally toenailed...even something like a Simpson H1Z which is getting very common is only strong in vertical uplift, it would be a useless bendy piece for transferring load across the top of the walls. Imo, only something like a structural screw (timberlok, etc) up thru the plates and into the bottom chord would be the start of a connection that would transfer the load. A connector purpose built out of steel would work, but that would be a specialty thing you wouldn't see on any normal build.
McMaster lists 1/4" wire rope as using a 1200# working load with a 5:1 safety factor. Being able to design a fastening strategy to transfer the forces to to the timber is a much bigger problem than the wire rope being too weak.
1. Unless there's a noted gap to close somewhere, likely resulting in nails elongating in the steel plates, the cable cannot compete with the compressive strength of the timber.
2. This is 100% reliant on the fastener(s) between the top plate and the bottom chord being able to transfer the cable load to the bottom chord. A lot of times its traditionally toenailed...even something like a Simpson H1Z which is getting very common is only strong in vertical uplift, it would be a useless bendy piece for transferring load across the top of the walls. Imo, only something like a structural screw (timberlok, etc) up thru the plates and into the bottom chord would be the start of a connection that would transfer the load. A connector purpose built out of steel would work, but that would be a specialty thing you wouldn't see on any normal build.
McMaster lists 1/4" wire rope as using a 1200# working load with a 5:1 safety factor. Being able to design a fastening strategy to transfer the forces to to the timber is a much bigger problem than the wire rope being too weak.
Radix2
Well-known member
Based on your observation that the truss bottom is sagging, the problem does not seem to be related to the walls bowing out.
It seems to be that with the low pitch, the upper and lower chords are simply sagging ( which doesn't make sense unless the truss members are really undersized or weak.)
Pulling the walls together may help, but unless you can measure them going out, you may want to think about what else might be wrong.
There should not be any out thrust on the sidewalls, you have members connected and taking all the thrust - the issue may be that the trusses are coming apart at the eves - not the connection to the building.
It seems to be that with the low pitch, the upper and lower chords are simply sagging ( which doesn't make sense unless the truss members are really undersized or weak.)
Pulling the walls together may help, but unless you can measure them going out, you may want to think about what else might be wrong.
There should not be any out thrust on the sidewalls, you have members connected and taking all the thrust - the issue may be that the trusses are coming apart at the eves - not the connection to the building.
James-W
Well-known member
I am confused and I need some clarification.
The bottom chord is anchored to the top sill plate on the outside walls. So if the bottom chord is sagging, then how can the outside walls be bowing outward? With a sagging bottom chord the outside walls should be leaning inward, not leaning outward.
The bottom chord is anchored to the top sill plate on the outside walls. So if the bottom chord is sagging, then how can the outside walls be bowing outward? With a sagging bottom chord the outside walls should be leaning inward, not leaning outward.
like2wheel
Well-known member
Thanks for asking. Was wondering same...
tjpavlov
Well-known member
Can you check old real estate photos to see if the sag were present when you moved in?
It's possible that the weight of the insulation and drywall was too much for the trusses. I know people who overstuffed their attics and their roofs sagged because of it.
It's possible that the weight of the insulation and drywall was too much for the trusses. I know people who overstuffed their attics and their roofs sagged because of it.
tjpavlov
Well-known member
Great question. I'm not an engineer but could the bottom chord sagging cause the weight of the roof to push more on the top corners of the walls rather than the middle? Perhaps part of the issue is with how the walls and joists are fastened.
lakeroadster
Well-known member
Please edit your details and add "SW Kansas" as your location
This is likely the issue.
BTK, Did you check to see if the truss lower chords were rated for the new dead load of the insulation and drywall you added?
And if they aren't rated for the actual load all the cables you are adding won't help the sagging truss issue.... but adding some ceiling joists will.
How wide is the garage?
What will you be putting back up for insulation and ceiling?
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mcbane
Well-known member
Those dont look like engineered, shop-built trusses. You sometimes see 2x4s in manufactured trusses but those are stress rated 2x4s with connections that ensure they can adequately transfer tension and compression forces without the connectors appreciably deflecting.
Even without sheetrock the trusses may have been inadequate for the span and loads (do you have snow? how many layers of asphalt shingles are up there?).
The last thing I would try to do is to put a cable in to add compression to a bottom truss cord that is already bowing. That might cause it to fail. The safest thing to do is ask an engineer to take a close look at the trusses and propose how you might prevent further sagging. If the official fix (probably doubling up your trusses) is too expensive for your budget at least the proposal will give you some ideas for a DIY repair.
Even without sheetrock the trusses may have been inadequate for the span and loads (do you have snow? how many layers of asphalt shingles are up there?).
The last thing I would try to do is to put a cable in to add compression to a bottom truss cord that is already bowing. That might cause it to fail. The safest thing to do is ask an engineer to take a close look at the trusses and propose how you might prevent further sagging. If the official fix (probably doubling up your trusses) is too expensive for your budget at least the proposal will give you some ideas for a DIY repair.
The Tool Tyrant
ALLIANCE MEMBER
BTK...personal message sent!
dave89iroc
Well-known member
personally? I'd wait till spring and replace the entire roof structure with new engineered trusses
Homerr
Well-known member
Tear the one, or more?, layers of asphalt shingles off and replace with a standing seam metal roof.
Appreciate all the help but I'm just not up on the roof lingo so I'm a little lost. 2x4s across the bottom of the trusses are defintally bowed. I will try and measure walls tonight to see if they are bowing out. I'm starting to think you guys are right about the walls not the issue and it's just weak trusses. If I did put trusses sistered in (11 total) how would I get roof back to square before I did that. Do I jack it up at the bowed part of the 2x4 or the middle? Any idea how much an engineer would charge to look at it?
matt_i
Well-known member
This is my recommendation. Find a good week of weather, order materials, take a vacation from work, and go to town while the sun shines.
As I look at the haunch plate it would not take much for that tie-plate to twist in a parallelogram type manner and allow the top chord to slide past the bottom chord at the interface. That would cause your sag...
matt_i
Well-known member
While it seems like a stronger steel gusset would be better, there's always the challenge of sawing the plate to size, then the pain of attaching wood to heavy-metal.
I better like the solution of making 3/4" plywood gussets in a much larger overall size, something like 24" horizontal and 16 (guessing) high to match. Then liberally use polyurethane construction adhesive like Loctite 3x or 8X and then "anti split point" torx drive screws like a GRK or ABC-SPAX, repeat same on both sides.
If you can support near the roof peak, and possibly also under the vertical center post of the truss, I think it would be safe to take off the sheetmetal on one side of one joint at a time and replace it with the plywood. Putting the ply over the sheetmetal does little good.
Hi, I would check the walls with a simple level to determine if they are bowing. then use a pole jack to level out the 2x4's and just sister them with a 2x6. do one at a time. you are asking just a little too much from the 2x4's. from the pictures it does not look that bad.
I've worked alot more with metal and have sheets of 1/4 inch steel laying around. If it would be better with metal I'm game. Plasma cutter will make quick work of any plates than need done. Will try and get level on wall today. Do i put a pole jack in the middle where they meet on bottom chord or 2 with 1 on each bowed part of the bottom chord. Each bottom chord has 2 bows in it.
wrenchguy
Well-known member
Use a dry line corner to corner on the inside along the top plate to check if walls are bowing out. In my 1st post i mentioned those are homemade trusses. I agree with everyone mentioning that it all the sag may be in the truss. In this case a engineer is gonna tell u to replace with cert trusses. I'd find ol'school carpenter to see if they can be jacked and plywood reinforced. With its 2x4 bottom cord i'd be concerned…. maybe with a 2x? sistered in may work. I see no problems with the paint cracking.
Radix2
Well-known member
At 2.5/12 pitch, It may be that you just don't have enough angle to make the truss work with that size of lumber and geometry- it would be interesting to go to a lumber yard and have them spec out trusses for you ( a good way to get some free engineering) and see how they compare to what you have.
Top and bottom chord sizes, how the triangulation is done, etc.
Once you have a better idea of what is required you could decide on a fix.
Top and bottom chord sizes, how the triangulation is done, etc.
Once you have a better idea of what is required you could decide on a fix.
FullRaceMerc
Well-known member
Have you run a string to see if the wall is bowed at the top plate? I think it would be important to determine exactly what all has moved to figure out the next step.
How long is the garage along the ridge? Gable ends? Garage door under a gable end?
How long is the garage along the ridge? Gable ends? Garage door under a gable end?
wrenchguy
Well-known member
lakeroadster
Well-known member
Your trusses aren't designed to support point loads on the bottom chord in the manner you are lifting it.
The vertical members just above the jacks will be the next to bow. They are columns, unsupported, and will buckle under compression.
What's your planned next step? to leave the jacks there?