[Stryker]

Sketching some framing into a plan, one to be built outside San Antonio. It is a plan from Alan Mascord Design Associates, and the plan shows engineered trusses.

Engineered trusses are a huge no-no in the S.A. market for custom home building. Commercial, light commercial, and production builders use them right an left, but few if any of the custom builders will use them.

So I'm examining the structure to see if a hand-framed stackup job will work, and how the details might look.

Rafters need to be 2x8 most everywhere due to large spans, figured using the 5 psf ground snow load, with some smaller spans using 2x6.

The design with trusses has a roof arrangement having a 12" heel height, which makes for a good eyebrow line with the 24" overhangs, so I did the bearings with the 2x6 ceiling joist frames being plated with a single 2x6, and the 2x8 rafters getting a full birdsmouth. The 2x6 rafters get a smaller one with about a 2" seat cut.

First pic attached shows this.

The garage is different, in that its ceiling spans are longer, requiring a ceiling frame of 2x10 joists. The 2x8 rafters, raised off the 10/0 wall plates, have no birdsmouth cuts, and bear on blocks cut from something. I say "something" because I am not sure the blocks should be from the #2 SYP stock used for rafters. But maybe that is OK.

Second pic shows the garage bearing situation.

Anyone see any issues?

Having crawled into a few attics in the S.A. area, I have seen a lot of roof frames where purlins and purlin braces are used, so as to be able to downsize rafter sizes. My second pic shows where there is an opportunity for this in the garage. Should I do this so as to be able to go down to 2x6s?

 

[ScipioAfricanus]

Purlin braces need to land on a bearing wall, that 2x in the picture is not a bearing wall.

On a side note, why are trusses a big no-no?

An energy heel truss will give you all the height you need for your insulation if done right.

Andy.

 

[Golden view]

There was another similar thread about raising the rafters instead of them bearing on the top plate. Metal straps are likely needed to resist rafter thrust in this case.

And a second on purlins needing to go to bearing. In that case they end up supporting about half the entire roof load.

 

[kiteman]

I think he just has to size the garage beam for the additional load. Why not use a 2x8 band joist on the garage to keep the plate height the same. We frequently do purlins to be able to use 2x6 rafters, even adding lvl's I the ceiling to pick them up.

I understand the preference for stick-built roofs on customs. It's mostly the same here, but trusses are becoming more prevalent recently.

 

[Stryker]

Thanks to all for the replies.

I knew the purlin situation needed to brace down to bearing, but was thinking that if that beam were sized appropriately, it would do.

Probably not worth it to size up the beam in order to go down a rafter size. Going to the smaller rafters, adding all the material and labor to do the purlins and braces, increasing beam size, heck, it is likely less cost just to go with the 2x8 rafters.

Texas has its own rules. I guess like anywhere, local practices rule, and it is no different there.

First and foremost, there is no plans review to get a permit. There may be in the major metro areas, but just over the city line, in the busy suburbs, no real attention to code when it comes to what is on plans. And no inspection to code.

You'll get inspected, but it is all about setbacks, driveway placement, stuff like that. Nobody's gonna tell you you gotta have hurricane clips or anything like that.

Plans consist of just a few pretty pictures, is how I see it. Floor plans, elevations that show roof pitches, maybe total height, plate heights and window heights, and maybe door and window schedules. Simple wiring plans. That is it. Nothing structural is addressed.

The practice is for the builders to hire the engineers that draw and spec the structural stuff, and they do this after getting the jobs and doing permits. They do it so they have someone else to lay the blame on for foundation and frame problems, and as a result, the foundations are grossly overdesigned, and the floor and roof framing slightly so, because the engineers don't want to get phone calls, either.

The light commercial guys and the production builders like Pulte, Centex, David Weekley, and others, all use roof trusses, and do so on the majority of their work. Look around the big metroplexes all over the Lone Star State and you'll see trussed roofs everywhere. But the one-off "custom" guys won't touch a trussed job.

They won't because they have low-tech low-cost framing subs, all-Spanish, that while they are talented roof cutters, are close to incapable of learning those new things you gotta know to erect and assemble a complex roof assembly using trusses.

But most of all, it comes to this. Every custom builder has his go-to structural guy that draws his slabs, and another one, or maybe the same one, that draws his roof framing. His "joist layouts" he'll call it. He knows his engineer is being careful and will keep them both out of trouble. He knows his framing sub will do things the same way every time, because the engineer is repeating his same details every time.

The builder will even cut out the engineer for the roof framing if he gets comfy enough with his framing sub, who he can count on to use those details learned job after job, and who will if in doubt, use twice the beam size necessary.

But the builder will not do a trussed job, simply because he doesn't know any truss supply people. He does not have to know them.

And that is why trusses are a no-no in Texas.

 

[Bearded Wonder]

I'm in Fort Worth not San Antonio, but for what it's worth...

Actually, the reason I don't use trusses is because they are more expensive than cut in roofs, unless you're doing something simple like a straight gable roof. Then the extra cost of getting the trusses made is offset by the speed of the labor to install. Most frame crews here prefer hand framing a cut up roof to installing trusses.

I know of three very good truss building outfits within 45 minutes of me, so it's not that the option isn't available.

On hand framed roofs, there are a pretty established set of rules (basically code) regarding joist and rafter size, hip and ridge size, purlin bracing, ridge bracing, strong backs, hog backs, etc. Most crews and builders adhere to it.

I've used Mexican crews, but my main framer is a ****** and runs mostly white guy crews. I've known awesome Mexican crews and sorry white trash crews. The worst crews and the worst construction that I love seen is on the big national type tract home builders who slap together whole neighborhoods as cheap as possible.

I've built a ton of houses and they're all (with the exception of the house I posted where the owner ran his own gas and the house exploded) still standing. No call backs for structure problems, so whatever we (the good custom builders) are doing must work pretty well.

We do kind of have our own rules here. From what I read from the guys in other regions, they would freak out over some stuff if they came down here.
That's a whole nother topic for a different thread though.

 

[wallmaxx]

Thanks to all for the replies.

I knew the purlin situation needed to brace down to bearing, but was thinking that if that beam were sized appropriately, it would do.

Probably not worth it to size up the beam in order to go down a rafter size. Going to the smaller rafters, adding all the material and labor to do the purlins and braces, increasing beam size, heck, it is likely less cost just to go with the 2x8 rafters.

Texas has its own rules. I guess like anywhere, local practices rule, and it is no different there.

First and foremost, there is no plans review to get a permit. There may be in the major metro areas, but just over the city line, in the busy suburbs, no real attention to code when it comes to what is on plans. And no inspection to code.

You'll get inspected, but it is all about setbacks, driveway placement, stuff like that. Nobody's gonna tell you you gotta have hurricane clips or anything like that.

Plans consist of just a few pretty pictures, is how I see it. Floor plans, elevations that show roof pitches, maybe total height, plate heights and window heights, and maybe door and window schedules. Simple wiring plans. That is it. Nothing structural is addressed.

The practice is for the builders to hire the engineers that draw and spec the structural stuff, and they do this after getting the jobs and doing permits. They do it so they have someone else to lay the blame on for foundation and frame problems, and as a result, the foundations are grossly overdesigned, and the floor and roof framing slightly so, because the engineers don't want to get phone calls, either.

The light commercial guys and the production builders like Pulte, Centex, David Weekley, and others, all use roof trusses, and do so on the majority of their work. Look around the big metroplexes all over the Lone Star State and you'll see trussed roofs everywhere. But the one-off "custom" guys won't touch a trussed job.

They won't because they have low-tech low-cost framing subs, all-Spanish, that while they are talented roof cutters, are close to incapable of learning those new things you gotta know to erect and assemble a complex roof assembly using trusses.

But most of all, it comes to this. Every custom builder has his go-to structural guy that draws his slabs, and another one, or maybe the same one, that draws his roof framing. His "joist layouts" he'll call it. He knows his engineer is being careful and will keep them both out of trouble. He knows his framing sub will do things the same way every time, because the engineer is repeating his same details every time.

The builder will even cut out the engineer for the roof framing if he gets comfy enough with his framing sub, who he can count on to use those details learned job after job, and who will if in doubt, use twice the beam size necessary.

But the builder will not do a trussed job, simply because he doesn't know any truss supply people. He does not have to know them.

And that is why trusses are a no-no in Texas.

So do you do "hurricane clips" and "all that stuff"?

Just wondering if you build the best structure possible, or just go along to get along? I'm thinking that some people can sleep well at night building a home that will structurally fail someday. Don't get me wrong.............I learned the Texas framing methodology back in the early 90s. Then I was re-educated to the importance of incorporating structural practices in WA state. Wind and seismic considerations are important. Blowing them off because its "not inspected" is not the right answer.

Just my 2 cents. I'm actually focused on that type of mentality and not necessarily you specifically.

 

[Stryker]

Well, I "framed" enough of it to convince myself it will be a routine job to do it as a hand-cut stack-up. Some posts here, beams there, no rafter purlins or braces used, I just figured the rafter sizings for whatever ridge-to-plate spans were needed.

Hard to believe, but San Antonio needs a 5 psf ground snow load for design. Much of the roof uses 2x8 #2 SYP rafters, with the shorter spans going with 2x6.

The plan design with its trussed roof, two-foot overhangs, and 12" heel height, made it such that I needed, as mentioned up front, to bear the rafters on plates atop the ceiling frame rims. This, everywhere but the garage, with its long-span ceiling frame, needing 2x10 ceiling joists. There I went with blocks under the 2x8 rafters. Pic attached.

Second pic shows the "normal" condition everywhere but the garage, where we'll have 2x6 ceiling platforms making up the attic floor.

As for codes, inspections, plans review, permitting, and all, I hope I did not infer those things are not needed or that I did not believe in compliance. I am a firm believer in code as a MINIMUM for building practice.

Only meant to say that things in Texas are a little different, with a large portion of its area having no plans review, and no inspection. Plus that thing about plans by architects and designers not including anything structural.

 

[ScipioAfricanus]

As designer and previously a GC I include structural design when I am allowed and/or when warranted.

My opinion is that I do not care for the connections you have for the RRs to top plate to CJs, but his is just my opinion. IBC and IRC call out for a certain number of fasteners at the RR to CJ connection, and I think your scenario does not address that adequately.

Also I do not like the RR bearing on the angled blocks, but this is just my opinion. Perhaps you have been doing it this way for a long time with no problems.

For what it is worth (not much) those are just my thoughts.

Andy.

 

[Stryker]

https://basc.pnnl.gov/images/site-b...d-top-plate-allows-more-insulation-underneath

The ridge is structural, and the CJ's are not providing any tying function.

We'll find out more when talking to the pro framer who will do this. Not selected yet.

In the mean time, for your viewing enjoyment, here is one in the neighborhood, in progress. Look closely.

 

[Birch]

Well, I "framed" enough of it to convince myself it will be a routine job to do it as a hand-cut stack-up. Some posts here, beams there, no rafter purlins or braces used, I just figured the rafter sizings for whatever ridge-to-plate spans were needed.

Hard to believe, but San Antonio needs a 5 psf ground snow load for design. Much of the roof uses 2x8 #2 SYP rafters, with the shorter spans going with 2x6.

The plan design with its trussed roof, two-foot overhangs, and 12" heel height, made it such that I needed, as mentioned up front, to bear the rafters on plates atop the ceiling frame rims. This, everywhere but the garage, with its long-span ceiling frame, needing 2x10 ceiling joists. There I went with blocks under the 2x8 rafters. Pic attached.

Second pic shows the "normal" condition everywhere but the garage, where we'll have 2x6 ceiling platforms making up the attic floor.

As for codes, inspections, plans review, permitting, and all, I hope I did not infer those things are not needed or that I did not believe in compliance. I am a firm believer in code as a MINIMUM for building practice.

Only meant to say that things in Texas are a little different, with a large portion of its area having no plans review, and no inspection. Plus that thing about plans by architects and designers not including anything structural.

I get the feeling you're not native to here . . . . :no: :whistling


Personally, I don't like your Garage roof framing solution with the little sloped stand blocks, (w/o seeing the whole plan, hard to understand why you feel this is necessary? . . . ). I would raise the ceiling the few inches to provide for a typical 3-1/2" Birdsmouth on the 2/10 rafters and provide more shear nails tying the, joist to rafter/rafter to joist, for better connections and thrust resistance.


Also, standard roll-up style garage doors fit better if the ceiling is 1' 6" higher than the top of the door, and more is okay too. Allows for easy hardware and auto door opener installations. So if you are tight on header to plate clearance, the plate should be raised for this reason too. (And I would not allow the foundation contractor to eliminate the curbs on the garage part of the slab and I'd have him make them two inches wider to the inside than the plate width too!)


I have used trusses over the garage and conventionally framed the rest of the roof on many large customs here in SA, TX. Just don't tie them together over a common ceiling.


Your other 'plate over joist' detail is ok, but again you are giving up ceiling height. (and I don't have a plan to view . . . for a clue .)

 

[knucklehead]

The older I get, the grumpier I get.
I could frame that in my sleep. It is simple.

 

[Stryker]

As a followup to all this drivel, I spoke with a San Antonio structural engineer, one I was referred to by a builder. He said no problem, it is done all the time, the biz of raising the rafters off the plates to sit atop ceiling framing, or even (gasp!) to use a heel stand block for a partial raise.

All done to retain the design intent, being ten foot ceilings, overhangs with fascia bottoms just above window-transom heads, and importantly, so as to be able to get full-depth attic floor insulation out close to the wall line.

Interesting, the way it works there. Builders either buy the service directly from a structural engineer to design and detail the roof frame, or indirectly from the lumber supplier, who provides it as part of the package.

Either way, the framer is obligated to do it per the engineered prints.

 

[Birch]

As a followup to all this drivel, I spoke with a San Antonio structural engineer, one I was referred to by a builder. He said no problem, it is done all the time, the biz of raising the rafters off the plates to sit atop ceiling framing, or even (gasp!) to use a heel stand block for a partial raise.

All done to retain the design intent, being ten foot ceilings, overhangs with fascia bottoms just above window-transom heads, and importantly, so as to be able to get full-depth attic floor insulation out close to the wall line.

Interesting, the way it works there. Builders either buy the service directly from a structural engineer to design and detail the roof frame, or indirectly from the lumber supplier, who provides it as part of the package.

Either way, the framer is obligated to do it per the engineered prints.

First of all, engineered trusses are not "a huge no-no" in the South Central Tx Hill Country area. Many Builders are preferring to go with them as they often can cut framing costs, and avoid structural problems that some less qualified framers may cause. With either type of roof, it should be "engineered" prior to the foundation's engineering so that the foundation will be built to support the structure as framed. Having structurally engineered trusses is a liability relief for the builder. If the foundation and roof engineering was done for trusses, then it should not be simply changed to a conventionally framed roof without prior consultation of the structural engineers (and vice versa).


Second, I did not read anything in the OP about increasing the Heel-stand to accommodate more insulation as may have been provided for on the truss details. The responses (drivel?) may have been different. My previous post was composed prior to your post about "Insulation", but I posted it late. It is not totally applicable to your amended scenario, but I left it unedited. I have the "clue" now.


Often any HO changes are designed by the builders, or framers, and the change plan is submitted to the engineer for approval. As a framer I would not use the small "Heel-stand blocks" as you have them detailed. They are simply prone to split, and I would not like that. They can however be simply turned sideways and made longer to follow the grain of the joist and will be much less prone to split, and serve the same purpose.


With structural Ridge Beams, I prefer to place the beam on-pitch and cut the rafters w/BMs and lap the top cuts over the ridge beam, and aside each other for solid connections, rather than butting the plumb cuts to the beam as you show. BMs are good, they resist thrust.


In the Framing biz, "You have to be smarter than the Builder". If someone tells you to do something stupid, and you do it, whose fault is it? If you see something that could go wrong, speak up! Stupidity is not a defense. There is no such thing as justifiable stupidity.


I wish you well with your project. I wouldn't use those guys down the street. :no:

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