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Rafter Blocking at Top Plate

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#21 ·
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.
 
#22 ·
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.
 
#23 ·
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.
 
#24 ·
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)
 
#25 · (Edited)
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).
 
#26 ·
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??
 
Discussion starter · #28 ·
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.

Image


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.
 
#33 ·
As I understand it here in The Peoples Republic of Kalifornia it is for shear transfer. I spec this same thing out from the floor joists and rim joists or rim-blocking to the bottom plate for the exterior walls. The Simpson 35s 16" O.C. typical. Shear transfer from foundation to roof

Boundry and edge nailing through the roof sheathing into the pressure blocking too.

Andy.
 
#34 ·
Warren said:
The top??? Won't the plywood do that?? Why would it matter more at the bottom of the rafter than anywhere else??
Click to expand...
Take a couple of 2-bys and lay them on edge in your driveway. Tack some OSB on top, then take a running jump and land on it from the side. Chances are, the 2-bys will collapse, no?

The top end of your rafter is well-fastened to the ridge (I hope), so it's not likely to roll. The compressive force up there helps with that, too. But down at the lower end, without blocking all you have is your fascia to resist roll.

Probably not an issue except under extreme circumstances, but i can see the logic behind it.
 
#35 ·
Never done it myself, but I always use 2x rough fascia, which I am sure performs the same function. I don't like restricting the airflow, and 1" isn't much after a few generations of spiders have done their thing.
 
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#36 ·
tin, that is a gross exaggeration of what the blocking does. We are not talking about just one sheet. If I laid 20 2x4's, nailed (not tacked) the osb, and then took the leap, you would see little to no reaction. Not to mention, the rafters are connected underneath via a birdsmouth, toe nails, and mechanical fasteners. Just because something is logical doesn't mean that it should be utilized always.
 
Discussion starter · #38 ·
reveivl said:
Never done it myself, but I always use 2x rough fascia, which I am sure performs the same function. I don't like restricting the airflow, and 1" isn't much after a few generations of spiders have done their thing.
Click to expand...
1" is the standard code ventilation thickness and insulation baffles are 1" standard. Code ventilation for attics last I remember was 1/150 which we easily have.

I agree though that the more you take away from the rafter bay, the less flow you have.
 
#39 ·
reveivl said:
Never done it myself, but I always use 2x rough fascia, which I am sure performs the same function. I don't like restricting the airflow, and 1" isn't much after a few generations of spiders have done their thing.
Click to expand...

I believe the 2x facia serves the same purpose as the blocking.
The same as a band joist on cantilevered floor joists.
Maybe Loneframer will have another slow weekend and do some tests like his joist blocking strength thread.:whistling
 
#40 ·
reveivl said:
Never done it myself, but I always use 2x rough fascia, which I am sure performs the same function. I don't like restricting the airflow, and 1" isn't much after a few generations of spiders have done their thing.
Click to expand...

Ive never blocked ether but i agree with the 2x rough fascia.. it keeps everything from rolling not that its going anywhere anyways IMO its toenailed and nailed to the cealing joists
 
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Dirtywhiteboy
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