I have a customer who removed the cieling joist from his garage.now there is a sag in the ridge.I have stripped the old roof off,before I knew this was done,and am waiting to reroof .I dont think it is structurally safe with just rafters and a 2x 8 ridge. any suggestions on the most cost effective repair?
I was considering temporarily supporting the rafters from both sides and putting in a 4 x 12 beam ,supported on the bearing walls on each end,then attaching the rafters to it. the span is 24 ft, the pitch is 4 12 .
Replies
don
The sizing of the new ridge beam is important, as are the continued support at each end down to the foundation. If the bearing point falls on an opening, the correct sized header needs to be installed to carry the load.
The most cost effective is to replace the joist. I'm sure the walls are bowed out.
Personally, I would start by getting some helpers, a couple of jacks and a couple of come alongs. I would slowly jack the ridge back up at the same time you pull the walls back in. Once you get it back close to spec, I'd put the joists back in and 'splain to the man that they do serve a purpose.
the cieling joist
did you mean joistS?
hmmm 24 ft span, basically, HO removed the bottom chord of the trusses, wonder why the ridge is sagging........
quick calc if the garage is 24 by 24, ridge would need to be a 6x20 gluelam
Bet the outside walls have a bow in them also?
What you have there is a ridge board, not a ridge beam. It's imporant to know the difference.
DANGER DANGER DANGER - Your are about to become part of a slideshow at the next OSHA conference!
At least with the old roof off there is less weight bearing down, but you are lucky you didn't take a quick ride down to the concrete slab along with a few tons of lumber and shingles! Beware - with that 2x8 bowing, that is the ONLY thing stopping a lumber storm from coming down on your head while you are working under it trying to shore it up. That whole structure needs to be red flagged and fenced off. At this point, the only way to safely relieve the stress would be to remotely jack it up - say with a scissor lift controlled from OUTSIDE the garage, or via a tele-handler and a loop of cable through the top
With it in the state it is now (bare deck and structurally unsound), I think the best thing to do now is find out what the client wants the garage to be like. The guy pulled out the joists for a reason... what was the client trying to achieve? If you go with a ridge beam, that might require a moment frame for the new door header as well. Scissor trusses might be better option - so long as the client understands he CAN'T modify them!
If you can - post some pics of this disaster in waiting!
Paul
Cool your jets.
It isn't a disaster waiting to happen necessarily..................
But then again, he hasn't been back.
I agree the threat of something catastrophic happening is below minimal. Wood structures just don't fail the same way brick ones will. I can point you to a hundred structures locally that have had sagging ridges and bowed walls for generations...not days, weeks or months.
The only catastrohic failures you hear about with wood structures are decks that are overloaded and collapse causing deaths in the worts cases.
I agree that conventionally built wood structures don't just suddenly fail. I used to live in the country, and I've seen barns and equipment sheds do the slo mo collapse over decades.
I would argue this is in a different catagory however. The owner has taken a conventional building system and radically altered it by taking out a critical structural component - the joists. Now, the only thing keeping the walls from blowing out and the roof coming down is the bracing provided by the front and rear walls, the top plate on the side walls, and the 2x8 ridge board. The only saving grace at the moment on that ridge board is it's load is distributed fairly evenly, and there isn't a sudden load point in the exact middle but rather a gardually rising pressure in the middle. The rafters are keeping it pressed more or less vertricle on the ends, but as the rafter heels in the center pull away more the 2x8 is going to pick a side that is weaker and flop over. At that point, the only thing keeping the lumber storm at bay is the pullout resistance of the nails... and that aint much, especially now they are being levered apart instead of being in shear as intended.
I agree with your analysis in almost all respects. In no way would I put any additional load on that roof as it is now or you could certainly see a catastophic collapse. That being said, I wouldn't hesitate to work on the building from the inside particularly if he were to start as I suggested and place jacks under the ridge and come alongs at the top of the walls.
<holding blankie tightly> I'm skaered! </holding blankie tightly>