Simpson ties v. toenailing Rafters.
TDRucker
| Posted in Construction Techniques on
Has anyone started using ties to attach rafters instead of cutting birdmouths and toenailing? What ties do you use? I have used “hurricane ties” AND cut birdmouths. (sometimes required) Has anyone used the Simpson VPAs? It looks like you don’t have to cut birdmouths at all. Is this worth the time/money ? Just wondering.
Thanks.
Terence
Replies
Going from memory, I think that Three 16D toe nails is good for something like 180# of uplift. Whether you neeed more than that depends on how much uplift the roof structure the roof framing generates.
And, of course - Codes can require anything they want without really having a good reason.
I always thought the Simpson VPAs looked kind of amateurish. But there's really nothing wrong with them as far as I know.
There obviously applied for cathedral ceilings and in my eyes would be a big PITA to work with and a take to much time. You have four steps to nail these things into the plate and to the rafter.
I nail two rafters on one end and two rafters on the other end and then slide my ridge in place and nail the rafters to the ridge brace and then move on and nail the rest of the rafters in by pulling the birdsmouth in tight and nailing off that's your guide and your done.
Maybe they would work better if you had a structural ridge already in place
These things you have according to them.
http://www.strongtie.com/products/connectors/VPA_SCL.html
VPA Installation Sequence
Step 1) Install top nails and face PAN nails in "A" flange to outside wall top plate.
Step 2) Seat rafter with a hammer, adjusting "B" flange to the required pitch.
Step 3) Install "B" flange nails in the obround nail holes, locking the pitch.
Step 4) Install 10d x 1 1/2" nail into tab nail hole. Hammer nail in at a slight angle to prevent splitting.
You would have to make a mark on the rafter that represents the outside wall plate and try and line that mark up to the hanger and make sure you nail it perfect so the overhangs line up. Without them there's nothing to line up pull the rafter in tight and nail it on to the next one. When your all done shoot the hurricane ties in.
I think it will take a heck of alot more time to use them as opposed to cutting a birdsmouth out of a rafter.
I don't think these were around a couple years ago when I did my roof. I got one rafter carefully cut to fit (with birdsmouth), and used it as a template to cut the rest. I looked at all of Simpson's stuff, and ended up just adding A-35's alongside the birdsmouth.
-- J.S.
Has anyone used the Simpson VPAs?
I've spec-ed them on three jobs, but two are pending, and the third I didn't get to supervise. We will see--the one building uses TJI, which are not very bird-mouth "friendly," so it may be interesting to see how it gets doen in practice. (The CM & I are kind of waiting to see if they will preinstall the VPA on the rafters, or on the top plates, after they "work out" what all that galvanized is for .)
It looks like you don't have to cut birdmouths at all.
That's what the literature shows. Which makes it a good solution for things like TJI, gluelams, etc. that are designed to be "entire," not notched.
Is this worth the time/money ? Just wondering.
That's a potentially much more complicated thing to answer. My building project, the CM & I ciphered up the costs to birdsmouth "standard" rafters to suit the job. Well, that was a no brainer, especially with dimensional lumber versus TJI on top of the labor costs. That's why we're both going to watch the "how" of the installation closely.
As the plan of this beast is two "salt boxes" run into each other at a 35º angle, there's a lot of exactly-the-same rafters (with some really long spans; and a boatload of ceiling joists at a slightly different angle 12" offset to the rafters). The question may be will the framers hire a small crane instead of Manueling the rafters up.
I just used VPA's to install BCI's (Boise Cascade's TJI). The specs for the BCI's allow birdmouth cuts, but you have to be exactly right on getting the bottom flange to fully bear on the top plate.
I'm doing this project for my own shop, and accordingly the extra time to deal with all of the bits and pieces wasn't that much of a factor for me.
A couple of thoughts on the VPA's, though...they seem to come "pre-adjusted" for a 12/12 pitch. I have a 12/12 and a 6/12. They are a pain to adjust for the lower pitches once installed, so you'd be well served by rough adjusting them before they go on the plate. With the BCI, you fold over a little tab and nail at an angle down into the bottom flange of the ceiling joist. With solid-sawn lumber, you're nailing sidways...so consider your rafter spacing and how you swing a hammer in that space; this was especially troublesome in a couple places where I had "cripple" rafters running on shorter spacing where a few skylights went.....
The other thing to look out for is matching your roof pitch to any gable ends. Since the VPA's force the bottom edge of your joist to the outside of the top plate (rather than a bird's mouth sitting on the inside edge of the top plate), you'll need to make sure the gable follows the slightly shallower pitch of the roof using the VPA's (or make the bearing wall shorter as required for the pitch and thickness of the bearing wall).
--Ken