I have 2 questions.

1. Do you block your rafter tails (not trusses)
2. Is this code to block rafter tails?

1. I do not block rafter tails and never have or been on a job where others have. My framing experience is limited exclusively to remodels (additions, etc) not as vast and awesome as yours :notworthy

2. It is not code (at least in the areas I work). Though more times than not the eng/archi specs a 2x sub fascia.

 

I don't always do it, but more often than not, I do.
I think of them as 2x insulation stops.

Everything you do to a truss system helps. ie: truss blocking, spacer strapping, couple of diagonal straps, ridge blocking.
Yes, the truss plant sends out a strapping layout, but usually with too few to straighten the trusses to the boarder's satisfaction.
I also run diagonals on the king struts from the wall to as high up as the length of available strapping allows.

no, not code here.

 

Stick framing: never.
Truss installation: as prescribed (typically always).

 

Never heard of this, what is going to keep the rafters from rolling.

Did a quick web search and found this from the National Institute of Building Sciences.

"Blocking and Lateral Load Paths for Roof Systems

Rafters and ceiling joists having a nominal depth-to-thickness ratio exceeding 5:1 (e.g.,2x10) need blocking at their points of bearing to prevent them from rotating or displacing laterally from their intended position. Rotation loads on rafters occur when the roof sheathing is resisting lateral loads perpendicular to the rafter because these loads are actually trying to move the top edge of the rafter sideways. Preventing rotation is typically accomplished by installing full depth blocking along wall plates between rafters and ceiling joists."


As for what code it is, not sure. But I am sure a inspector around here would have a fit if he saw us trying to get away without blocking.

 

I have only on commercial buildings with trusses. I don't think I have ever done it on a house

 

I was not trained to do rafter blocks at top plate.

But about 15 years ago we were framing a place and a experienced carpenter that I had not worked with before started putting them in because that's how he always did it.

I really liked how strong it made that all feel. sort of plums the rafter. I can't stand rafters that aren't plum. makes a great insulation block and leaving the gap for the very important vent.

Come to think of it seems under-built without them.

 

I don't have any code books where I am at right now, but am still searching.

This is from the UBC in 1994.

Sec. 2326.12.8. Blocking. Roof rafters and ceiling joists shall be supported laterally to prevent rotations and lateral displacement when required by Section 2306.7. Roof trusses shall be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.



I'll find some more, but in 30+ years we have always done it and it was required per plan. Maybe it has to do with the seismic zone we are in.

 

I have never installed rafter blocking but I read about it in Larry Haun's book. It seems like a good idea to prevent rafters from twisting. I think it looks better with the blocking.

Rafters and ceiling joists having a nominal depth-to-thickness ratio exceeding 5:1 (e.g.,2x10) need blocking at their points of bearing to prevent them from rotating or displacing laterally from their intended position. Rotation loads on rafters occur when the roof sheathing is resisting lateral loads perpendicular to the rafter because these loads are actually trying to move the top edge of the rafter sideways. Preventing rotation is typically accomplished by installing full depth blocking along wall plates between rafters and ceiling joists."

Does that take into account the birds mouth cut and the pitch? Or is it just related to nominal rafter size?

 

Found it.

2006 IRC
R802.8
Lateral support. Rafters and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation.


We have alway used 2 x 12's, so that is why it was required. And if I remember right Washington and Oregon did not adopt the IRC until 2001 or 2003, we used the UBC before that and as stated in that UBC code ref I posted earlier it was required period regardless of rafter size.



Edit.

From the 2009 IRC

R602.10.6.2

1. For limited height rafters or trusses (i.e., =9.25-in. heel height), blocking is not required in low wind and seismic regions. This requirement establishes a reasonable limit on the generally accepted past practice of not providing eave blocking.
2. For conditions beyond this limitation, e.g., taller heel heights or in higher seismic and wind regions, “partial height” eave blocking is required to comply with one of four options. Three options are prescriptive framing details. The fourth option is for the connection to be designed in accordance with accepted engineering practice.

 

Here in CA. we have always done it, (included rafter blocking) and I spec this out on my conventional light frame construction details. I refer to them as "pressure blocking" and I spec out 'A-35 nailed all holes' as well 16" O.C.

It is just something that I have always done and always been expected for the conventional stuff.

Andy.

 

Here in CA. we have always done it, (included rafter blocking) and I spec this out on my conventional light frame construction details. I refer to them as "pressure blocking" and I spec out 'A-35 nailed all holes' as well 16" O.C.

It is just something that I have always done and always been expected for the conventional stuff.

Andy.

We have to do those pesky A35's now also. Must be because we are both in higher siesmic regions. Damn engineers have gone nuts with these, we have them all over the house.

 

Here in California every residential or commercial job I have been on has blocking at top plate where rafter is connected. It is not unusual to have the roof sheathing blocked every 4 feet & at the ridge for shear nailing. 6"oc nailing is often called out at the rafter/top plate blocking without the other blocking.

 

Probably a good idea since you have so much stand on those rafters

 

H1 & H2 & the A35 are all very common stick or truss.

 

Now don't forget the Simpson LS series of hardware. Had to put LS70's on vented birdblocks on a trussed roof every bay or other. We also had to nail the bird block from the sheathing. Which was becoming the norm. However that was the year they changed the venting requirements so the 3 hole vent block became a 4 hole vent block. Ended up having to use non tico rated nails :shifty: The blocks couldn't handle the nailing other wise.

Then that same year on a stick frame had to put LS90's on every rafter that connected with a ridge, hip or valley.

 

I think that it is unanamous in Calif. I've never seen it done without blocking and I assumed (incorrectly, I guess), that it was done everywhere.

 

with a 1" air gap minimum at the top for airflow to the bays. Like this.

Yes, but not like that. What's to stop critters from getting in there?

 

Closed soffits. You mat be thinking about open soffits out there in Seattle. That's all we did when I lived out there was vented bird blocks. (3) 2" holes every 24". Here we have vent strips or vinyl in our soffits as the primary critter stopper.

I just found this unusual, especially on gable roofs. I have 3 primary reasons why I do this.

Shear transferance
Take the twist out of rafters at plate
Insulation block

 

We do not do it and I have never seen it done or heard of it. I have built many houses that were either stick framed or trussed, and worked with several different engineers and architects. We are required to install the simpson rafter/truss ties at the end of all rafters/trusses. Not sure why the block does anything for the insulation. What do you mean by "insulation block"? I can see how there would be some structural help provided but it does seem like overkill.

 

Always, everytime, and without fail.

The first framer I worked with was from Florida, and that is where I picked it up initially. I never considered it a code issue, since we do it everytime, and if it wasn't, I would still do it.

 

Hey Warren , I have always enjoyed reading your post and is one of the reasons I joined here.

When we say insulation blocks, I'm most familiar with batts so think of that highly skilled insulation installer up in the attic putting the batts in the rafter bays it keeps the batts from migrating out into the soffit.

I can see how you could look at this as a extra step but to me it seems worth it. Do you have another method to plum the rafters at the top plate. Before this method we would go along with a square and plum the rafters when we were nailing our first sheathing board.

 

I've done it on commercial jobs where the specs call for it. Never done it on residential. Most of the time the rafters are 2x6 with a 1/2"-1" birds mouth so theres not much heel height. I've never seen the need.
Good thread though, I love to get insight on how its done in other parts of the country.

 

no blocks
95 percent engineered trusses
wall sheeting down 3/4 from ttp
nail sheeting scraps to wall plate for ins stop
mini strap hangers on every truss(only some are required seems easier just to do them all than go over every truss sheet checking uplift)

 

I'm just starting to read this thread, but if you are talking at the plate, it is required like it would be for joists. Here it has to be in plane with the top of the rafters for shear nailing of the sheathing.

If you are talking at the end of the tails, no I've never seen that done.

At the plate line though it is required. We cut a notch in our blocks for air or if its trusses, we use the supplied blocks with holes drilled and screen over the vent holes.



R802.8 Lateral support.
Rafters and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation.
R802.8.1 Bridging.
Rafters and ceiling joists having a depth- to-thickness ratio exceeding 6 to 1 based on nominal dimensions shall be supported laterally by solid blocking, diagonal bridging (wood or metal) or a continuous 1-inch by 3-inch (25 mm by 76 mm) wood strip nailed across the rafters or ceiling joists at intervals not exceeding 8 feet (2438 mm).

 

Jeff. I understand that it could be used to stop the migration of the insulation. Here though, usually the insulator will install his cardboard or foam baffle and then use a short piece of fg insulation at the wall.

Question to the guys who do install the blocking: Won't the hurrican clip keep the rafter/truss from moving laterally?? Isn't that wood block a poor insulator compared to fiberglass? I guess if its code where you are then you don't have a choice.

Speaking of code, here is a new one that I heard from a NE Ohio inspector. This guy seems very knowledgeable and claims this has been code for a while. He wants the iceguard to hang down over the fascia 3 inches, and then the roofer must break a 24" strip of coil stock to the roof angle and apply at the entire eave over the iceguard, and extending down over the fascia. Supposedly the gutter guy then can slide his gutter up behind the coil stock. He made a roofer do this on a job we were at. Has anyone ever heard of such a thing??

 

Question to the guys who do install the blocking: Won't the hurrican clip keep the rafter/truss from moving laterally?? Isn't that wood block a poor insulator compared to fiberglass? I guess if its code where you are then you don't have a choice.

By lateral movement they mean the top rolling or tilting.

 

Must be a Regional and a preference thing because I've never done it either.

 

Here's a better picture of what I mean. I cut the rafter tails 6½" then put a 2x6 to leave a 1" air gap at the top.

The lateral support (2x6 in my case) is to keep the top of the rafter or truss from rolling. It is IMO the same as blocking the ends of the joists on a bearing wall.

I'm not saying that it is structurally unsound to leave them out. The house is not going go anywhere.

I was assuming it was a standard practice and I went looking for concrete evidence, but found only what was listed above in the IRC. I guess I was defaulting to the west coast seismic application.

 

I was wondering the same as well