Well, the trusses came in and the crane showed up and we put them up one at a time (doing this by myself) and nail-gunned the ridge blocks in as I went along. Well, I got pretty p*ss*d off after more than half the toenail side hit the truss nail plate and just bent away or around, not penetrating into the truss wood. The upper nail went in ok because there was wood above the nail plate. The crane guy (15 yrs construction experience) said that was just the way it goes sometimes. Sometimes the lower nail gets through and sometimes it doesn’t. The bent nails prevented the ridge block from sitting flush to the truss and by the time we got to the end (26 trusses), the last truss was about 1/2″ out of plumb (maybe more, I haven’t measured). I got to thinking about this and wondered what was to prevent me from nailing each ridge block to the side of the truss centerline joint, alternating sides as I go along. That way, there is a straight shot into each end of the ridge block, through the nail plate, into the truss. I can’t think of any logical reason why this wouldn’t be OK but, since I’m probably the most uneducated construction guy in the world, thought I would just check with the pros.
Edited 8/16/2006 3:46 pm ET by JimJ
Replies
Here in south Florida probably 95% of the houses have truss roofs but I've never seen anyone use blocking between the trusses. We usually use 1" X 4" temporary strapping at the ridge, eave line and in the midle and then come back with a couple of 2" X 4" perlins nailed on the underside of the top chords.
Well, ignoramus that I am, I just put in what the truss maker sent along. Ridge blocks for the top and vent blocks (with holes) at the ends (eaves?). That's how they said to put them in and that's what I did. The crane guy said that's how it's done here (San Diego), so that's how I did it. What's a perlin? I can follow the 1x4s for spacing but putting them up one at a time doesn't let that work too well. I can go back and rip out the ridge blocks to get the spacing back in line but I still want to know if offsetting the ridge blocks is OK? I don't have a problem doing the offset but I don't want to screw something (that I don't know about) up.
Yeah, I got some of the metal spacers from Simpson to put the trusses in but the crane owner wouldn't let my 'bracero' workers come up on ladders (long story) so I had to go it alone up there. At $150/hr, I had to get those babies swung up and in place as quickly as possible so I couldn't take the time to use them. So it was, swing it up, place it against a pre-installed bracket at the bottom, and nail the ridge block in place - and repeat. I was well aware of the dangers of accumulated variations and had planned to trim the ridge block, if required, as I went. Just didn't have enough time. Looks like I should just go back and undo them one at a time and re-nail it properly using an offset. That way I can adjust if there is any deviation. Lots of work but I would rather have the spacing exactly right. As said, putting the plywood up will be a b*tch if it doesn't fall on the truss just right. It's too far up there for me to have to deal with offline centers.
I'm not what I would call a truss guy (or truss only guy) by any means but it sounds to me like you're doing your first trussed roof (and doing it without experienced supervision too). I've only done about a hundred of them and while I have loaded a lot of them with a crane I have never stood any of them with a crane. That sounds horribly expensive too me. Typical crane expense for the average home should not exceed the 2hr minimum charge. That includes travel time both ways, setup, loading, and break down. Usually the crane is on the job for less than an hour. Some bigger jobs have required additional charges because of multiple crane position setups and multiple buildings. Worth every penny for loading them, but not for rolling them.
Here in my neck of the woods (St Louis) we use a 49 1/2" 2x4 so we can set two trusses at a time (one truss per chain). 49 1/2" is the outside to outside measurement of three trusses on a 24" layout.
After the gable and sister truss are set and braced off, you can use the 49 1/2 to secure the next two trusses to the ones that are already standing. Clear as mud, right?
Jeff
Several years ago I started using a crane service to set our trusses.
If there is any way to make it work in the schedule, the crane is brought in.
The houses I do are reasonably modest by most standards (under 2500 sq ft + garage), But I can set them in three hours (usually two) with a three man crew plus the crane operator.
The crane service I use is $95/hr.
Money well spent
Terry
Jim I just reread one of your posts are you saying that they sent you blocking already precut? both ridge and for eaves?
"I just put in what the truss maker sent along. Ridge blocks for the top and vent blocks (with holes) at the ends (eaves?). That's how they said to put them in and that's what I did."
hmmm ... that would definenately be a new one for me. what kind of material was the eaves blocking.
Hmm, - the eaves blocking was 2x4 with 3 vent holes; the ridge blocking was solid 2x4. Enough eaves blocking for both sides (of course) and enough ridge blocking for a single line at the top. The eaves blocking also serves as a brace at the bottom place where the truss rests on the outer wall. The included instructions detail how to install the eaves blocking between the trusses so it must be 'normal'. One of the pictures on the installation does show the ridge blocks offset, although not mentioned in the instructions.
sounds like something specific to your area, or even your truss manufacturer. That eaves blocking sure is something out of left field.
But one thing I will tell you, if your truss manufacturer specifies a certain procedure and you don't follow procedure then you could run into liabilty issues, as well as inspection failure. your inspector will require a copy of your truss lay out and bracing details and he will look to see if you have followed it.
so the least I can say is, you are doing the right thing by following the specifications.
Jim - the cumulative effects of being off a little each truss can really add up. I'd reset the last truss plumb - 1/2" will not hurt much but may make sheathing less fun. Be certain those things are braced well, diagonally etc.
Your idea of offsetting the blocking is a good one for next time. Typically we use the metal truss spacers (if we have some) or 2x4 blocks nailed on top of the top chord. Every couple of trusses its good to measure back and check layout - correct as necessary.
Here in Toronto, Ontario we cut the blocks at 22-3/8" and install them at the peak of the trusses before we stand them. Nails dont always go in straight and many ricochet once they get through one side of the gang nailer. Very rarely are the trusses out of plumb when plywood begins...
That's why I use old fashioned 16d commons when nailing thru truss plates. No ricochets.
Faster and easier is not always best.
16 commons?!!!!
I remeber pouring 50# into the porch backfill back in the 70's. That was the last box that the boss ever brought us! LOL!
The blocking doesn't need to be installed when the crane is there. The trusses could/should be temp laced and the ridge blocking put in later. I wouldn't allow ridge blocking to be the only brace holding up my trusses. I don't trust nails that are in withdrawl if my life depends on it. In that situation, my life would be depending on it and I'm going to lace them up better.
And faster.
blue
Ridge blocks are not braces. They're just for plywood edge nailing. Therefore, no withdrawal issues.
SamT
Jim --
Look for a response to this from Boss Hog. He's Breaktime's resident truss guy, designs them for a living.
-- J.S.
I don't really know what to add here. There's no structural reason to have ridge blocking. Seems to me that it would be in the way of ridge venting.Other than that, I don't know what difference it would make either way.
I don't do trusses every day but have done plenty. The only times I used a crane was on two log houses as the trusses were extremely heavy. Before i install a truss we chalk line down the top of one wall 2 inches in from the corner to use as a reference on each truss. We do all the lay out and install the simpson ties ("hurricane clips"). Then we install the first truss, usually a dropped gable and brace it nice and solid and plum. Then one by one we install the remaining trusses, using a couple of step ladders and a yoke stick to tilt them up. Every fourth truss we install an 8 foot brace that is premarked at 24 inch centres. We use 2 steel braces per truss along the way. I have never used ridge blocking since the engineering does not require it. Usually less than a daywith two helpers we have the roof trusses up.
Have a good day
Cliffy
We usually do not block trusses right at the ridge. Instead, we run two rows of blocks, on the flat, each 1" from the ridge. This gives us a 2" ridge vent space and full edge nailing for the plywood.
Never block trusses as you install them. The first one up gets braced, the rest get strung together with 1x4 nailed across the top. I have some 16' 1x4s with 24" centers laid out on them for setting trusses. Same as everyone else said, pretty much.
Depends what the code is in ones area. sounds to me like you require blocking. But it is most likely for edge support for your plywood. if you can look it up in your code it will tell you. if you don't have a copy of your local code you can ask your inspector. I never heard of blocking over the plates, that's new to me....I call that your sub facia or "nailer", but at the end of your overhang.
when you have blocking over the exterior wall plates with venting, that's a detail for when you have exposed rafters, and unless your house is el cheapo you would be using some finish lumber ( like cedar or fascia board stock or whatever) but not regular 2x4
last time I looked at my local code I couldn't find mention of "ridge blocking" but what I did find was that 1/2" ply requires edges support minimum of 2"x 2" (1.5 x 1.5) edge support includes the use of "H" clips but since one can't put a clip at the ridge we all use 2x4 solid blocking.
since edge support is the point; then what you propose ( alternating) would not work. 2 rows one each side would work as someone has suggested,
often in the past our crew would ask the builder for 5/8" ply instead of 1/2" so that we would not have to deal with the hassle of H" clips, also then, we did not need to put in any ridge blocking.
on another note...unless these are some kinda Monster trusses wouldn't it be cheaper to have the trusses layed on top of the walls and get a helper or 2 to stand them up with you. then temp brace them as others have suggested,and then put in your blocking later.
as far as the 1/2" out of plumb. thats easy to work with. just make sure the 2 end ones are plumb. make your last block 1/2" shorter and you can work with that. try to lay your sheathing so that you never have a joint on that truss, then you wont have to worry about a screwy cut. if you do have to lay some joints over that trusses it's probably faster to scab some extra 2x4 on for the little bit of extra bearing.
you can also knock the last 2 blocks out instead of the last one and have 2 out a 1/4" instead of 1 out 1/2", that is called splitting the difference.
> I never heard of blocking over the plates, ....
It's required here in earthquake country.
-- J.S.
just got back from my response to Jim...
"it's required here in earthquake country."
well there you go.
hurricane ties for hurricane country...earth quake blocking for earth quake country.
Edited 8/18/2006 2:40 pm ET by alrightythen
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The blocking over the top plates are for houses that don't have a closed soffit. We call 'em "bird blocks" here to keep the birds from making nests in your attic :) The holes in the blocks have a fine mesh stapled over them to keep birds and bugs out. If you have a closed soffit, its pretty much a waste of time putting them in. Don't know about the "earth quake country" requirements but that sounds logical to me.Jeff
same as what I described earlier, cept I refered to it as exposed rafters, as opposed house without closed soffit.
I dont think that is what he has here, as what you and I have both described is an architectual detail. something that would not be included with a typical truss layout, let alone supplied by them. he's got 2x4's with 3 holes drilled in them. soffit blocking as I call em would usually get more like one 2" hole per block.
PS..The mesh is old school...they have vent plugs that fit snugly into various size holes that look much nicer IMO
Edited 8/19/2006 12:07 am ET by alrightythen
These blocks in question were supplied by the truss manufacturer. That's the only thing they can be, is the "soffit block" or "bird block" as I call em.Jeff
were not connecting on this....you and I are talking about the same thing But I do not beleive that is what he is supplied with. the holes are for ventilation, so yes there are holes. Bur as someone pointet out some areas have blocking over the plates for structural reasons. this is different then the " birds blocks as you call em"
ask jim if he will be installing soffit, or Jim can you tell us. That will clear up what they are for. I do not believe that the truss co would be supplying " birds blocks" as that is part of the exerior trim work, and the not part of the framing.
But I could be wrong as he lives in a different area then I do.
Are they calling out for "Bearing Blocks" anywhere on truss layout ?
"Are they calling out for "Bearing Blocks" anywhere on truss layout ?"
Bearing blocks wouldn't be at the ridge - They'd be at the bearing walls.
I see what your saying, I finally get it :) Even though the blocks have holes in them they can be for ventilation in a closed soffit where the blocks are being used for lateral stability, right?
Every set of these blocks I've put in are perpendicular to the top chord of the truss at the top plate to keep bugs, birds, squirrels etc. from getting in the attic space. Since these blocks do have holes in them, that is really the only place they can go since putting them anywhere else defeats the purpose of having holes in the blocks.
Since this would be the location of the blocks, it would be part of the framing and there will be no "exterior trim work" in conjunction with these blocks since they will be under the plywood and "in" the soffit if there is in fact a closed soffit. Here in St Louis, the open soffit would be painted black before the siding goes on to kinda hide it really. (generally this system is on "lower end" track homes here) These blocks may be entirely for earthquake protection or as per code requires in the area, I'm not saying they aren't.
On a side note, I'm not trying to argue with you, I'm enjoying the conversation! That's why I came here to meet people and talk about my passion of building houses!! Jeff
cheers ..... I wasn't either. It just seemed like we were talking about the same thing as far as the "birds blocks" go, but that, what he has is actually not birds blocks, but structual blocking. which is new to me, but I guess some areas need it.
The way that you install your birds blocks is the only way I've seen em done; perpindecular to top cord as you described. In fact only 2 weeks ago I installed some "birds blocks", I used 1x4 fascia board with 2" holes and vent plugs.
I have a feeling Jims blocks are installed right angle to the top plate so that they are nailed to the trusses and then nailed to the plate as well.
If the trusses were on 16" centers we would'nt use blocks, probably, but 24" makes for a pretty weak span on the plywood at the top (especially when the minimum code is 3/8 - which has been supplied once that I can recall). The rest of the roof has clips to help stiffen the roof plywood. I am not even sure if the ridge blocks are code but I will find out this week....never seen a truss roof without these installed here in Toronto...they are just nailers and spacers certainly not bracing...brace as we go along
I think this is a good example of how regional building is. Sometimes I see blocking up at the top, but never in the peak - as someone above said - it blocks air flow for the ridge vents. As far as blocking above the wall plates, never seen it here except on open eve houses. What do they call 'em? bird blocks?
If your truss manafacturer supplied them and it's shown on the truss layout sheet I guess it's required.
not all houses have ridge vents.... just to point out