Gambrel Roof Overhang Details

[Dennis Putnam]

I am planning to build a shed with a gambrel roof. However, I cannot find any good details about how to build the overhangs on the gable ends. From what I've read the gable ends are built the same as the rest of the joists except wall studs are added but nothing about overhang.

Can someone post a link or explain it to me? Thanks.

[Steve Rozmiarek]

Dennis, most gambrel roofs on the barns around here have an overhang similar to the eaves, assuming that is what you are thinking, the way I would do it is inlay a 2x6 on the flat into the outside rafter/truss (the one the gable wall mounts too), so that it gets but nailed to the second rafter/truss in. Use this cantilever to support the overhang framing, sheet with the rest of the roof and done.

If you want to go further and use one of the bigger overhangs, like what they used on gambrels that were designed to support winches, it takes more framing.

[Dennis Putnam]

Thanks for the reply. So the end trusses need to be build different to accommodate the cantilever extensions. Do you have some info on how to build that? I am guessing it needs to be done after all the interior joists are in place.

[Mark Bolton]

Dennis,
I think what Steve is referring to around here is called a drop gable when dealing with a truss manufacturer.

http://hitec.ca/images/droppedGable.gif

They simply build the gable truss smaller by the thickness you intend to frame your overhang. It was common when sheathings werent as robust as they are now but it seems now everyone around here has moved to full size gables and they simply frame the soffit out with 2x material outbound of the gable. The overhang is often built while the gable is laying down and tipped up provided you have the means to tip it. The only time this becomes an issue is if your overhang is going to be very large and your concerned with sag. We go 18" commonly.

The only issue we have ever had with the drop gable is if there is any hump/sag or slight misalignment in that gable its carried right out to the sheathing. If the gable sits even slightly high or low it will pitch your last few feet of sheathing up or down substantially. Its critical to get that truss in the right spot.

[Steve Rozmiarek]

Right, place all the trusses, including the end, not the overhang framing though. Then use your circular saw to cut a relief that a 2x6 on the flat will set into and be flush with the top of the truss. One end of that 2x6 is but nailed through the second truss, the other is butt nailed to the overhang framing. This cantilevers the overhang on the outside two trusses. The end truss get modified in place, it is just a normal truss, albeit an end wall truss, so the cross ties are usually different. Kind of hard to explain, I think I have a pic of the last one I did, will see if I can find one.

BTW, that tag like is pretty clever.

[Steve Rozmiarek]

Dennis,
I think what Steve is referring to around here is called a drop gable when dealing with a truss manufacturer.

http://hitec.ca/images/droppedGable.gif

They simply build the gable truss smaller by the thickness you intend to frame your overhang. It was common when sheathings werent as robust as they are now but it seems now everyone around here has moved to full size gables and they simply frame the soffit out with 2x material outbound of the gable. The overhang is often built while the gable is laying down and tipped up provided you have the means to tip it. The only time this becomes an issue is if your overhang is going to be very large and your concerned with sag. We go 18" commonly.

The only issue we have ever had with the drop gable is if there is any hump/sag or slight misalignment in that gable its carried right out to the sheathing. If the gable sits even slightly high or low it will pitch your last few feet of sheathing up or down substantially. Its critical to get that truss in the right spot.

Sort of Mark, rather than building a gable truss that has a different height dimension though, I was describing doing the same thing, just inlaying the cantilevers into a truss that was the same height. Either would work fine I'm sure, if you are ordering the trusses though, I would use the drop gable like you pictured. I used the other way last because I built in place, and was marrying an old structure to a new.

[Jim Andrew]

So are you going to build trusses or stick frame the roof? I have stick framed a gambrel, and used ridge boards at each end of the rafters. If you did it stick frame, you could let the ridges run long, and nail your overhang to the end of the ridges.I'm talking using 3 ridge boards. And if you use a subfeisha, you would be able to nail your end rafters all from the end. It might also help to know the width of the building.

[Dennis Putnam]

I need to resurrect this thread as I am still a little fuzzy on the details. This is a stick frame roof with a ridge beam. I intend to extend the ridge beam, the knee wall top plate and the eve bottom plate as cantilever supports for a false truss. Can I then simply use spreaders (nailed from the outside of the rafters) along the lengths and will that be sufficiently secure once the sheathing is applied?

[Mark Bolton]

Im not sure enough of all your talking about cantilevering to say whether I would do it or not. As Jim mentioned cantilevering three ridges and simply landing on your fascia would work however without the support at the three breaks its questionable as to whether you would risk a sag over time.

How big are your overhangs going to be?

Steve's option, or the drop gable/truss, is by far the most robust as you have continuous support at every lookout and whether your stick building or truss framing its not a difficult detail. In a conventional gable there is simply the support of the fasica and false rafters but they are not broken as they are with a gambrel.

Depending on the size of the building and if your overhangs are modest (<16") I wouldnt be worrying about it too much.

[Dennis Putnam]

The overhangs will only be 6". Steve did send me some information off line but at the conclusion it did not provide the detail I needed. To be honest, I simply did not understand Steve's description for tying it in and there were no images of it in the plans he sent. The main vulnerability point, I think, is really just the eve. The ridge beam is 2X12 and the knee wall plate will have a 2X6 on its face. The eve plate is just a 2X4 on its back.

[Jim Andrew]

What length of rafters are you talking? What Steve meant is you can notch a flat 2x4 or 2x6 into the rafter over the wall, and butt your overhang rafter to the notched in board. It is just an extra board to help carry the overhang, but a 6" overhang will not present much chance to sag. A wider overhang is ok hanging on the flat lookouts. I have hung 2' overhang on flat 2x4's with no problem, I put them 4' oc on the plywood breaks, so you can nail the edges of the sheets.

[Mark Bolton]

Yeah, Jim's right.. 6" is nothing. The roof sheathing alone will carry that. We all probably should have asked sooer how big a building and how big on the overhangs. If you run lookouts at 24" o/c toe nailed into the gable rafter you'd be more than fine. Heck, your lookouts are only going to be 4 1/2" long heh.

[Jerry Miner]

Dennis--this is probably more than you need, but I drew a pic of a "typical" gambrel overhang with the type of lookouts people have been talking about. It is probably overkill for your project, but i wanted to help you understand the "flat 2 x 6 lookout" concept.

259058259059

The first pic shows a 2 x 6 lookout, the second shows the overhang with the "barge rafter" or "fly rafter" atached.

[Dennis Putnam]

Ohhhhhhhhh! I thought notching joists like that was a no-no without sistering. "Now I see," said the blind man as he picked up a hammer and saw.

Yes, I don't plan on much of an overhang. The shed is only 20'X17' and the overhang is just for aesthetics not functionality. I take it then that you are saying I don't need to bother with the notching and can just use spreaders while the cantilevered breaks will carry the load of the false trusses. I didn't think there would be much load but I just didn't want the false trusses falling off with age from loosening nails.

Thanks.

[Steve Rozmiarek]

Dennis--this is probably more than you need, but I drew a pic of a "typical" gambrel overhang with the type of lookouts people have been talking about. It is probably overkill for your project, but i wanted to help you understand the "flat 2 x 6 lookout" concept.

259058259059

The first pic shows a 2 x 6 lookout, the second shows the overhang with the "barge rafter" or "fly rafter" atached.

I haven't been here for a week or so, Jerry thanks for posting that excellent explanation, that's exactly what I was trying to describe.

[Jerry Miner]

Ohhhhhhhhh! I thought notching joists like that was a no-no without sistering.

It is acceptable at the gable end because the gable end rafters are supported by studs (not shown in the drawing).