roof sheathing for exposed rafter tails
Hello All,
Newbie question here. I’m building a detached garage to match my 71 year old house which has exposed rafter tails. I put up my roof trusses (which have extra long rafter tails for this purpose), and sheathed one side of the roof with 1/2″ OSB. Only then did I take a look at the exposed eaves and realise that it might not be kosher to have unsupported 1/2″ OSB at edge of the roof on 24″ centers. My intention was to go back and add some beadboard to the underside of the exposed sheathing to improve the appearance. Should I beef up the edge of my roof? One thought I had was to rip off a few inched of the sheathing and replace it with some planed-down 2×4 stock which I will have a rabbet to support the exposed OSB edge. Any thoughts? Thanks -John
Replies
Can you post any pictures? Sounds like a 2x4 fascia board is what you're describing. They leave osb exposed under eaves all the time here, 24" o.c. too - but there is usually a fascia at the edge of the roof. How would that affect the overall look?
You're right, I wouldn't want 1/2" osb unsupported at the edge, on 24" o.c. rafter tails. When I built my shed, I used 5/8" osb on 24" o.c. rafters, unsupported at the edge.
"I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
Not exactly a fascia board I think. I was thinking more of replacing the last few inches of OSB with solid wood sheathing made up of a planed down 2x4. I would also route a lip on the edge of the 2x4 to catch the edge of the OSB. From your reply, I may be able to rip off the last two feet of 1/2" OSB, rip a little material off the top of the exposed rafter tails, and replace it with 5/8" OSB. Attached is a picture of what I have so far. -John
The 5/8" over just the eave area should work. I painted the edge, then covered it with a metal drip cap. But the resulting bump from 1/2 to 5/8 might show a little, even if you bevel the edge. Maybe put some shims under the edge of the 1/2" sheathing, prior to installing the 5/8"."I needed a drink, I needed a lot of life insurance, I needed a vacation, I needed a home in the country. What I had was a coat, a hat and a gun."
Raymond Chandler's Philip Marlowe
I was thinking of ripping a little material off of the top of the rafter tails before nailing on the 5/8". That way there wouldn't be a lump. Of course, a 1/8" lump may not be noticable after the shingles are on.
You could use 3/4" T&G beaded board over the exposed areas, and then transition with a few cedar shingles back up to the halfinch sheathing, to "blend" in. The shingles don't mind.Parolee # 40835
You can also rip a 5/16" notch on the tail above the 3/4" t&g. This will plain out with the 7/16" osb.
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Chuck Slive, work, build, ...better with wood
Right on. I like the 3/4 thickness, so's the nails don't poke thru.Parolee # 40835
"You can also rip a 5/16" notch on the tail above the 3/4" t&g. This will plain out with the 7/16" osb."
Yes, but far easier done with the rafter on the bench, as you did, than already up and in the air.
For a top end job, one can oversize rafters (if needed) and do the tail rip at 3/4", sheathe the ends in the 1x beaded or v-groove, then roofsheathe over all. Use roofing nails the right length atop the overhang, of course, but hey, your total substrate is now at 1-1/4" or more.
If on a budget, use 5/8 T-111 just at the roof edge, no rafter detailing needed, the transion between the plywood and the 1/2" OSB is about minimal enough to ignore, so roof right over, but use 3/4" nails and set that gun correctly.
No transition for us here in snow country, as code requires 5/8" min sheathing.
Our yards only stock the 8" center T-111, so it's not as cool as the look if using 4" O.C.
I've seen architect's details showing 3/4" boards at the exposed roof part, going to 1/2" sheathing above, handling the step by tacking in cedar shingles cut down so the butts are 1/4". Nice little transition ramp. Easy for an archie to draw, tedious to execute.
It's interesting that a number of us seem to "double sheath" the exposed eaves -- once with beadboard, then a second time with regular sheathing. As noted, it makes a beefier surface for nailing.
I hadn't thought about notching out the top of the rafters to accommodate the bead -- I've just furred up to match instead. But it's something I'll keep in mind for larger roofs.
Our yards only stock the 8" center T-111, so it's not as cool as the look if using 4" O.C.
You can also get beadboard in a 4x8 panel format -- have you ever tried that?
No. The reason the T-111 make sense to us is that it is a proven exterior product. We're not aware of that in beadbord-pattern ply.
I hadn't thought about whether the beaded ply is rated for exterior use. I'll ask at the lumber yard and see what they say.With that said, I have seen it installed lots of times on porch soffits. Although technically "outside", it never sees any weather, although it would be exposed to wild humidity changes.
Thanks everyone for all your suggestions. I asked the local building inspector about it, and he was more concerned about having untreated rafter tails exposed than unsupported 1/2" OSB (which he said was not a problem). My house has untreated SYP (longleaf pine) untreated exposed rafter tails and they are just fine after 71 years. I told him I planned to paint them and he was OK with that. Since I already have the sheathing on, this is what I've decided to do. I'm going to notch the top of each rafter under the sheating so that I can slide a 1x4 treated board under the edge of the sheathing to reinforce the edge. I'm going to tack beadboard underneath the exposed OSB on the eaves and gable ends and support it on the rafters with a small piece of molding. With everything painted I think it will be OK. The beadboard is rated for exterior use as long as it is protected from rain.
JP,
Sounds like a plan. Get plenty of primer/paint on all cuts and rafter tail ends.
Chuck Slive, work, build, ...better with wood
I did something similar to what others are talking about - see attached.
I used 5/8" T-111 with 4" centers. Notched the rafters 5/8" and sheathed over that with 1/2" plywood. Worked out pretty well. I would highly recommend priming and painting at least one coat of paint before installation. Not the easiest thing to paint after installed....
Craig Z.
The reason the T-111 make sense to us is that it is a proven exterior product. We're not aware of that in beadbord-pattern ply.
Gene,
I followed up with a call to my lumberyard. The beaded ply that they offer is, in fact, rated for exterior use.
So there's one more option for you.
Ragnar
jpattillo,
I don't believe code will allow for the 1/2" OSB to be left exposed.
Here in Ore. any exposed overhangs must be CCPTS or better plywood, or solid lumber. The overhang is considered a "weather exposed " area and requires appropriate materials.
Your 71-year-old house probably had beadboard at the eaves. If so, what would really look best (and give you a stronger product, too) is to use beadboard on your garage, too. Of course, the level of detail you're willing to put into your garage is a subjective thing and something I can respect.
When I'm doing roofs like you describe here, I'll use beadboard at the exposed areas. Then I put furring strips on the rafters to match the thickness of the beadboard. Finally, I sheath the whole thing with either 1/2" OSB or CDX. This way, the continuous sheathing makes the roof strong, and the exposed eaves have about 1-1/8" of thickness to allow for good nailing without the points sticking through your beadboard.
Since you've already sheathed half your roof, you may not want to pull it off now. ;) Others here have mentioned running the beadboard and then just transitioning to the sheathing with your shingles. That should work, too, of course, but does not have all the benefits of what I've described above.
Edited 5/18/2007 1:25 pm ET by Ragnar17
With exposed soffits, I like to rip down the the top of the tails 3/4". Then I sheath the tails with 3/4" T&G beadboard and then sheathing right over everything with 1/2" or whatever is spec-ed out. This gives you at least 1 1/4" of nailing for your shingles without nails popping through. When no fascia is to be installed, this addtional thickness means the drip edge isn't hanging down below the sheathing.
Replace a strip os osb with 3/4"x 6" pt lumber. The quarter inch difference between the osb and the pt is made up with 30lb felt strips.Three strips staggered in width will add up to about 1/8" to 3/16", this feathers the difference out in three feet of width.I would add blocking between the rafters where the osb meets the pt, H clips inbetween the osb joints. 24" centers is a lot for 1/2" osb,if you do not have H clips installed , block all the joints with 2x3's or 2x4's on the flat from underneath.Easier said then done, if you have help it will go pretty fast.
mike