Sagging trusses in detached garage

[zak77]

I don't want this thread to turn into a similar thread so i'm going to keep this short and sweet. At my grandmother's house she has a detached garage about 22x22 that was built in the early 80's if i had to guess. Very simplistic design(2x4 walls, t-111 siding, truss roof structure). The issue is that my grandfather stored lumber for woodworking from the trusses, which was a fair amount of weight and as a result it caused the entire roof to sag. I'm up in Mass so the snow did not help matters at all. So is it even possible to correct this sag?? Or does it involve truss replacement?

I'm not looking to do this right away but at some point my mother's going to inherit the property so i'd just like an idea on what can be done. Probably about the same time i tackle this, it probably will need a new roof so i might as well do everything at once. And honestly i dont know if the trusses were homemade or bought.

I dont have pics at this time but if you were to look down the ridge, i'd say the center has sagged about 4".

 

[matt_i]

Pics will certainly help

In basic terms, if its time for a reroof, then it might be wise to strip off some of the decking, and place something like a doubled LVL beam in its place (with some analysis to support the sizing of course, but in general I trust a 1-3/4" x 11-7/8" LVL more than a 2x12)

Another idea, the sag could be potentially jacked out by supporting from the concrete floor, but you are into a long column which would want to buckle. But succesfully and slowly done, if there is room at the ridge, additional timber could be sistered both sides and possibly at the bottom (inverted "T" shape) and fastened at appropriate intervals.

 

[1969]

Hang tight there lad, class is about to begin.

 

[ishiboo]

Yeah, we really need pictures. It would take a lot of wood to sag a properly engineered truss system. Are you 100% sure it isn't a stick built roof and only the rafter ties are sagging?

 

[Jim Riseborough]

Well at least you started this thread out correctly, and not a scatter brain like the last one.

Is the wood gone now, or is it still there, might get it out if its still there.

some pics are needed, then we can come up with a solution that will work for you.

 

[zak77]

The wood was removed shortly after my grandfather passed away so there's no longer that concern. The ceiling height isn't that tall, maybe 8' max so there's no room for an lvl or any sort of center support. They are most deffinately trusses.

I really dont know of a way to correct this and if there is no simple solution such as jacking and somehow straightening the trusses, then it's simply a matter of replacing the entire roof system. Not sure if i'd go trusses or stick build it the next time around.

I'm not sure when i'll be at my grandmother's house so pics may be weeks out.

The real issue was the lumber was supported by only 2 trusses. One near the very rear of the structure and one a little less than half way into the structure so the majority of the load was at about the halfway mark. I'm questioning if these trusses were engineered or homemade but either way it's not what should be happening to a proper roof system.

 

[theoldwizard1]

Most of the time, when a roof sags, it is because the walls bowed out. Carefully measure the distance between studs on opposite walls at the bottom plate and at the top plate. If the top measurement is more than 1/2", that is a lot.

It could also be just separation of the bottom chord at the nailing plates or the bottom chord slipping on the top plate.

You can pull it back with a come-a-long, some 2x6 and cable with turn buckles. First pull the two opposing studs in (not required if the top and bottom measurements of the studes were within "spec"). Go slow. If the bottom chord of the truss has sagged, jam a 2x6 under each side of the joint(s) to lift it back to level, while you are pulling on the walls. Once the walls are back plumb and the bottom chord is level, make some over sized "nailing plates" out of 1/2" plywood to go over the existing nailing plates. Use one on each side of the joint. Attach with construction adhesive and screws/bolts.

Let the construction adhesive cure at least 24 hours (check the tube for cold weather cure time). Carefully remove the 2x6 braces and come-a-long and see if it holds. You may have to rig cables and turn buckles to hold the wall in place.

If the bottom chord has slipped from it original place on the top plate, use a hurricane truss connector (Simpson H1 or similar) to hold it in its proper location.

 

[matt_i]

If trusses of any kind I'd look very closely at the timber connections. Its possible one or more separated under the load, and that/those could be repaired by pulling back the gap and refastening. Its also possible that one or more of the truss members cracked thru a weak spot like a knot or the like, and the broken timber is consipring to deflect the roof.

I was assuming in my earlier post this was a classic ridge and rafter roof. Properly built & unmodified trusses would be more rigid in my estimation.

 

[ssdave]

Theoldwizard and Matt j have covered it well.

The first thing to do, is find out where the trusses have displaced, so you can see what needs correcting. As matt j said, find out what connections are damaged or displaced. Then, use cables and turnbuckles or a come-along to pull things back into shape. Using a jack and props to help will be a plus.

Once things are pulled back into position, adding braces and connections to hold things into place will be required. Leaving the cables and turnbuckles in place on the bottom chord permanently might be appropriate.

Then, remove the props and monitor it for awhile. You might have to re-tighten or adjust things as the trusses take back up the weight and settle into position. With some judgement, you might over-adjust slightly to allow for some relaxation after the temporary supports are removed.

 

[ms fowler]

When I read these "truss" threads I am amused at how the term "simple truss" has come to mean "it can be easily modified in whatever manner anyone wants to ".
There is nothing simple about a simple truss. The OP of this thread is to be commended for asking for advice before committing to a "fix".

 

[Jim Riseborough]

When I read these "truss" threads I am amused at how the term "simple truss" has come to mean "it can be easily modified in whatever manner anyone wants to ".
There is nothing simple about a simple truss. The OP of this thread is to be commended for asking for advice before committing to a "fix".

I agree, yet I am being chastised for posting **** here by administrators. Having professionals on these sites is what makes them work.

 

[James-W]

Is the building in good condition except for the roof? What I am getting at is, if the rest of the building is rather run down then it may not be worth the time and the expense of doing the repairs. In my opinion it would be best to do a very thorough inspection of the building and see exactly what it will take to fix it up properly.

 

[bczygan]

This thread really needs photos.

Typically, if a roof is overloaded, something will move and members will be damaged.

Check the side walls for bowing out at the top along their length. It will be more extreme in the middle. This will cause the ridge to lower in the middle, causing a swayback condition. It may crack the ridge board if it has rafters. Is this a gable or hip roof?

If the roof is ready for new shingles, now is the time to do it. How many layers does it have?

BTW, an LVL or other beam can be installed above the bottom chord of a truss or ceiling joist, to support it from above.

To help us determine if it is indeed a truss system, tell us, how far apart are the trusses?

Are there trusses along the whole length of the garage about 2' apart?

Bill

 

[zak77]

The structure is not in bad shape, average condition for an 80's garage with typical upkeep.

I think the roof has 2 layers of shingles on it and they are in good shape, reroofed about 20 years ago, wow it's been that long?? I do believe the trusses are 2' OC but not sure. I never took a good look at the under side of the roof or upper portion of the trusses since there's insulation between the trusses and i just never bothered to pull it down and take a look since any repairs are years out.

I am not concerned with the structure collapsing at this point. I know i've got to deal with this at some point in the future which may be 2-10 years out. I just wasnt sure if trusses can be "corrected" or if once they sag, that's it. It's not a dwelling so there isnt an immediate concern about life and limb but at some point my mom is going to own the property and i want to keep it in good shape for her.

 

[umtallguy01]

Whatever you do carefully price it out. Trusses and sheathing are cheap and if you need to reroof it anyway...

Sent from my ALCATEL A564C using Tapatalk

 

[James-W]

This thread really needs photos.

Typically, if a roof is overloaded, something will move and members will be damaged.

Bill

I agree totally. Pictures of the entire building, pictures of the roof, and then some pictures of the trusses themselves showing the roof sheathing.

 

[bczygan]

And this is really the time to make an assessment of the entire structure including drainage and foundation and everything.

I would be tempted to strip the roof, if the top layer is more then 10 years old. And I never like adding a second layer to a roof.

Bill

 

[kbs2244]

I agree on the need for PICs.
But, based on the build date, I would doubt it is a "truss" built roof as we know it today.
I am guessing it is "conventional" rafter and tie joist roof.
Maybe with a joist to ridge board splice vertical support at the mid point.

If so,
Get all the weight possible off it.
Look at a way to jack up the ridge board while pulling the walls back vertical.
Think of using those sheet metal joint reinforcing things at the joist to top plate joint.

 

[Justanoldguy]

I agree on the need for PICs.
But, based on the build date, I would doubt it is a "truss" built roof as we know it today.
I am guessing it is "conventional" rafter and tie joist roof.
Maybe with a joist to ridge board splice vertical support at the mid point.

If so,
Get all the weight possible off it.
Look at a way to jack up the ridge board while pulling the walls back vertical.
Think of using those sheet metal joint reinforcing things at the joist to top plate joint.

I spent many years doing truss roof builds from mid '70's on.
Your guess that it's not truss is really not based on anything is it?

 

[DougWil]

Residential trusses are typical designed for a 5psf bottom chord load. Basically sheet rock and insulation.

Grandpa probably way overloaded those trusses and with years of time and heat up by a warm roof have taken a permanent set, much like a bow, or other bent wood that has been steamed and bent.

You aren't going to straighten those trusses out.

 

[CNGsaves]

Please don't tell me the guy who built the "Ultimate Shed" . . . .
. . . . . which was EPIC thread with loads of pictures . . . .
wandered into your garage and did some work in the rafters/truss area !! . .

Without pictures, this thread is like asking Ray Charles how your haircut looks !!

 

[KenC]

Another request for pics. My reason: it is almost impossible for a true truss to sag without breaking. The bottom chord would have to become shorter, pulling the walls together, while to top chords become longer, pushing the walls apart. So pics to clear up what is really in place.