Reinforcing gable overhang ladder to prevent sag
I’m looking to add a slightly deeper gable end overhang to a detached garage structure. My understanding is that on new construction the gable end truss would be dropped 3 1/2″ to allow for cantalevered outlookers to support the overhang. However this is a retrofit and it’s just not an option to modify the gable end truss. The roof structure is site built trusses (plywood plates, 2×6 bottom chord, 2×4 top chord and web, 24 ft. clear span). Gable ends are standard vertical 2×4 on the flat and supported by the wall. The original 12″ saggy overhang was just the plywood roof decking with the barge rafter tacked on.
I’d like to do a 20″ overhang and understand that there are sag and snow load issues with just tacking on a ladder to the gable. My idea is to install blocking between the gable truss and the first common truss, then tie the ladder to the blocking with two Simpson HTT5 tension ties, one attached to the ladder and one to the blocking and bolted through the top cord of the gable end truss. It seems like this would effectively tie the ladder and the blocking together? It also doesn’t seem like a 5/8″ bolt through the gable end would cause issues (especially compared to notching or trying to drop the top chord of the gable end)?
Illustration of idea is attached.
Replies
The tension ties are a waste of money. You could accomplish the same thing with threaded rod going from the fascia to the first common truss, but you're still depending on a 5/8" bolt to resist bending. You'd be better off with an angle with 4 smaller bolts. If you are able to work from above, I'd let in a steel angle, from the first common truss to the fascia. I just had to repair a sagging overhang that was seriously under built. I used gallows brackets at the ends.
I agree with Mike. The tension ties will lead to the mating surfaces of the wood framing compressing into one another, thus allowing future sag. Better to support from beneath if possible. Corbels can be designed in traditional and contemporary ways.
Yep...
... gravity's NOT your friend in this endeavor.
Mike's got your back, his advice is good for a permanent cure.
With the roof structure you've described there's little latitude for adding support sufficient to resist the additional weight of the overhang you want, whether or not there's a snow load for three or four months.
I agree that the bolted ties are not the answer. I'm not even sure they'd work.
Are you taking the plywood off the roof? At least near the gables?
If you are, a 2X4 laid flat could be notched into the gable and cantilevered out to support the fly rafter.
I usually do that 4' O.C. so it catches the plywood breaks. If you want more strength you could do it 2' O.C.
couple other options...
I agree with the other replies. YOu're not going to overcome the overhang assembly torque with those connecters. You could tighten the heck out of those bolts, but your moment arm is still way too short.
As Boss says, notching the top of gable end for a 2x on the flat is a better idea.
Also, you can:
1. support it with a 2x on the flat going under the truss top cord--if your overhang detail can accomodate this thickness. See attached photos for an example.
2. add structural sub fascia. If you can cut back your truss tails to work in a cantilevered sub fascia like this, it will do a world of good toward resolving the gable end overhang load. I believe the gable end overhang for his project were 26" and soffet eaves were 36".
If I were going to try to use tension I'd want the member in tension to run across the top of the joint, to better take advantage of "leverage" -- ie, use a strap across the top. But one of the other suggested fixes would probably be better.
I would expect you to try that Dan
Wow, you'd be taking full advantage of another 1-3/4" of moment arm with that steel strap. Big deal. Sure, it's slightly better, but still nothing to write home about. For that matter, the roof ply is giving a similar tensile strapping effect. IMO, the additon of a steel strap over top of broken lookouts is not going to adequately do the job. As I stated earlier, the high level of torque here needs to be addressed by other means.