Truss Heel Blocking
Truss Heel Blocking
(OP)
I know this topic has been discussed in quite some depth in previous discussions. However, I would like to get some more input regarding raised heel trusses and what you have seen done by the truss manufacturer in your local areas with regard to supplying pre-manufactured heel blocking.
Most of the work I've done or at least seen constructed in my area tends to be non-raised heel trusses with bird blocking similar to the two examples below:

However, lately I've seen a couple jobs with fairly significant raised heels (12" - 24"). I'm not sure if this is a trend but in one case the truss plant supplied little frames for between the trusses, do you see a lot of this in your area? If the raised heel is too high then a solid 2x block is not practical in my opinion, what do you do in this case, shear panels?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
Most of the work I've done or at least seen constructed in my area tends to be non-raised heel trusses with bird blocking similar to the two examples below:

However, lately I've seen a couple jobs with fairly significant raised heels (12" - 24"). I'm not sure if this is a trend but in one case the truss plant supplied little frames for between the trusses, do you see a lot of this in your area? If the raised heel is too high then a solid 2x block is not practical in my opinion, what do you do in this case, shear panels?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com






RE: Truss Heel Blocking
Even though, structurally it is probably optimal.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
DaveAtkins
RE: Truss Heel Blocking
I will admit, most people in my area just ignore the rollover of trusses entirely.
RE: Truss Heel Blocking
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
I guess they are really no different than interior shearwall shear panels other than they are usually short enough so that a block will suffice. I will probably just use the same detail with a few minor modifications when the block height exceeds some set value (ie. 14"-16").
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
I think most of the problem (in my area at least) is many of the existing homes from pre 1970's have essentially a 2x6 heel depth so rollover was a minor concern. And since the introduction of 12 and 14" typical heels the old engineers turn a blind eye, and the new engineers are never taught that it should matter.
RE: Truss Heel Blocking
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
1- general rule in our office is if the heal is greater than 24" and we are the project engineers we supply either blocking or small truss every 48" c/c
2- if nothing is shown on the client supplied dwgs that were sealed by a P.Eng, then we do not provide anything, but do place a disclaimer that diaphragm transfer to plates and shear wall is by project engineer.
As has been discussed above, if we were to include them as part of our package, we would calls from contractors stating that they haven't seen that before and won't put them in, couple that with the competitive market we are in, our competitors certainly don't do it so we are sort of stuck in doing what the industry does.
Cheers
paolo
RE: Truss Heel Blocking
Ain't that the truth. I struggle with that everyday.
This is from the North Carolina code.... (see attached)
RE: Truss Heel Blocking
I've never provided any blocking or load path material from top to bottom chord.
We HAVE, on some occasions, specified the exterior, 7/16" OSB sheathing to be full height to bottom of top chord. Whenever we have parallel chord trusses that also provide a parapet, without overhang, naturally the exterior sheathing goes all the way up to top of parapet. That has GOT to account for SOME significant bracing.
I always specify an "H1" hurricane tie, which does have verticals both sides of the truss, but, i hesitate to think that that little bit of steel is the cure. It IS 2.75" of 18 gage.
I also would like to see blocking or other adequate material as a code requirement.
RE: Truss Heel Blocking
Go North Carolina! Seriously, that's bloody great.
This topic always ends up feeling like a diaphragm blocking PTSD support group.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
RE: Truss Heel Blocking
Thoughts?
In my opinion the venting should come secondary to the structural concerns. Pop a few small holes in the sheathing below the 2x4 shear panel top plate, but not too many that the sheathing is overly compromised.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
RE: Truss Heel Blocking
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
Specify the top chord proper vent. The sheathing should only go up to bottom of top chord. The proper vent will break that sheathing plane.
Trusses i typically deal with, come with only the top chord cantilevering for the pre-manufactured overhang.
The soffit is framed by the contractor and then the vented aluminum soffit is installed.
Am i missing something?
RE: Truss Heel Blocking
RE: Truss Heel Blocking
You have no idea the detailing norms around here. They'd make some engineer's skin crawl. Granted that's on the residential side of things, which thankfully my firm generally avoids except for preferred clientele.
RE: Truss Heel Blocking
RE: Truss Heel Blocking
FFS indeed. Now jayrod and I will be yet another step behind the state of the art.
Technically, those widdle shear wall panels need to be able to resist vertical shear or T/C on their sides to be in equilibrium. And, in many instances, you get that by fastening each panel to the last vertical of the truss such that vertical shear is passed across the truss from one panel to the next. Where that is the case, I would very much argue that the panels are just an extension of the primary shear wall rather than a whack of new, short shear walls. I guess, by the book, you'd still need to connect the mini-wall boundary studs at the far ends to the boundary studs of the primary shear wall. I would not want to be the first to specify that in my domain.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
We do just that...
RE: Truss Heel Blocking
I don't know that this is really any better than my first shear panel but at least it positions the vent holes up high out of the way of the insulation and it gives a solid nailing surface for the sheathing to the vent blocks. It does get us back to using the A35 clips though, so back to messing around with hardware.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
Dik
RE: Truss Heel Blocking
Beautiful. You're living my dream man! Got one for when the walls terminate at a location where it's not an exterior corner? When I imagine it in my head, it's hard to get the edge of the nearest truss heel panel thing to line up with your boundary studs below.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Truss Heel Blocking
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
Your illustrations are really cool!
You should write a book. It could be called, "Blocking Between Truss Heels and Other Things Contractors Don't Want to Do."
DaveAtkins
RE: Truss Heel Blocking
R602.10.6.2
RE: Truss Heel Blocking
RE: Truss Heel Blocking
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
If the wall sheathing extends up over the raised heel without a break then yes this is a major advantage to the roof construction as far as uplift and even truss overturning, the question is do most contractors do this or do they just break the sheathing at the top plate and then patch on more sheathing at the raised heel?
That is why I like my 2nd option with the heel block on top of the shear panel. This allows the contractor to terminate the sheathing at the underside of the top chord of the truss, the sheathing is continuous up the entire wall and over the raised heel. The heel block then provides an uninterrupted load path to the roof diaphragm. I don't see the validity in those shear panels with an air gap between their top plate and the roof sheathing, load cannot be transferred through thin air.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
since walls are generally 8'-1 1/8" or 9'-1 1/8" this is less of an issue than you think. They start the sheathing at the sill plate on the foundation wall, span it over the floor system, and then up the wall. It usually means the 8' mark from the bottom of the sheathing ends up being a foot or two below the top plates. The good home builders alternate whether the infill piece is at the top or bottom.
RE: Truss Heel Blocking
The downside of Option #2 is that you have both shear panels and heel blocks to install, but I don't supposed you would need the shear panels every truss bay, just over the identified shear walls and maybe every other bay where no shear walls are present, I guess it really depends on how conservative you want to be.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Truss Heel Blocking
I will Post a detail later.
IF you aren't supplying blocking, how are you justifying your load transfer.
RE: Truss Heel Blocking
Hopes and prayers mostly