# Rafter thrust and I give up



## jar546 (Oct 30, 2013)

Another framing queen is at it again.  Once again "I've been framing for 25 years".I'm starting to think that there should be an exception for those framing for more than 20 years to continue to ignore the codes.

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## MASSDRIVER (Oct 30, 2013)

OK, so I've been framing 26 years.

Have to ask; What else is in there? is that just a matching fill for the room? Do those rafters on the right keep going up to a beam or whatever? If that's just fill it should be OK with some adjustments. In other words, do the "purlin rafters" push on the wall on the left?

Brent.


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## RJJ (Oct 30, 2013)

Massdriver I tend to agree. Hard to tell what is going on with the entire issue from the photo.


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## Mac (Oct 30, 2013)

Hate to see the birds mouths cuts so deep - indicates a lack of layout skills.


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## jar546 (Oct 30, 2013)

There is no ridge beam, otherwise what was the point of posting this.  What you see is someone trying to create a vaulted ceiling on one side of a house.  The ceiling joists on the left simply terminate on a wall.  Those would have been the rafter ties but now they are not.  There is nothing prescriptive about this installation.  In addition to this being flagged at plan review, so were the 12" return walls in the garage with 10' ceilings but since we allowed them to put in the foundation to be nice as to not hold them up, they decided they would just frame while they were at it.


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## mjesse (Oct 30, 2013)

What do the approved plans indicate?

I agree with Brent and RJ, I don't necessarily see a violation in the photo provided.

Not every house is going to be framed with straight gables and flat ceilings, which is all the Code seems to really address in detail.

There is merit in the empirical methods used by carpenters, whether the inspector likes it or not. It's very likely that this same design has been specified by an architect or engineer at some point, and "works" just fine.

It's important that we don't get hung up in the belief that, just because it's not specifically in the Code, "these guys must be hacks"

There seems to be a common inspector mentality that all contractors are ignorant cheating crooks. Likewise, contractors think inspectors are incompetent wanna-be tradesmen.

That being said, there most certainly are ignorant, incompetent, cheating, wanna-bes on both sides. :devil

mj


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## steveray (Oct 30, 2013)

They could continue those short 2x4's across and it might work...(bottom third?)


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## tmurray (Oct 30, 2013)

jar546 said:
			
		

> ...but since we allowed them to put in the foundation to be *nice* as to not hold them up...


And there is the problem. You were nice. I tell people I'm not nice, I'm reasonable. If you can explain why there should be an exception to the rules for you and it makes logical sense I will allow it. Otherwise you will be treated like everyone else. Being reasonable I can be consistent, that's a lot harder when you are being nice. We have a plan review submission requirements that are more rigid than any other jurisdiction around and the first time through it always leaves a sour taste in the contractor's mouth, but during the project there are usually no problems because we caught them all on paper. second time through the submission process the contractor is all to happy to comply because he has seen all the money he has saved after we caught mistakes the first time around.

I think every once in a while we hope that being nice to someone will be reciprocated to us. We expect that they will work with us instead of fighting us on every little thing. All too often the reverse happens and being nice makes them feel like the rules mean nothing and all they have to do is complain a little to get their way. In my experience a stop work order fixes that.


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## steveray (Oct 30, 2013)

Didn't see that on quick glance....never did understand that or the seat cut that extends a foot into the room I am starting to see....



			
				Mac said:
			
		

> Hate to see the birds mouths cuts so deep - indicates a lack of layout skills.


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## jar546 (Oct 30, 2013)

mjesse said:
			
		

> *What do the approved plans indicate?*mj


That's the problem, there weren't any.  In my post above yours I stated that they only had a foundation only permit and decided to move forward with framing even though I had flagged this during the plan review which was still not complete at the time of this photo.  I gave an inch to be nice and let them get started before the weather changed and they took a mile.

This is not prescriptive and needs to be addressed by an RDP.


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## mjesse (Oct 30, 2013)

jar546 said:
			
		

> This is not prescriptive and needs to be addressed by an RDP.


Agreed.

But _*IF*_ the RDP signs off as-is, are they no longer "framing queens"?


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## MASSDRIVER (Oct 30, 2013)

jar546 said:
			
		

> There is no ridge beam, otherwise what was the point of posting this.


Well I don't know, Too-early-in-the-morning-haven't-had-my-coffee-yet-Mr. Smarty Pants.

So basically they just decided to not have a flat ceiling anymore and vaulted it up without the approval of the government. With no ridge beam to carry the rafters. Got it.

Damn Tea-partiers, bunch of renegades.

Brent.


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## jar546 (Oct 30, 2013)

Brent, it's early and you need coffee buddy but you're still thinking with clarity.  Nice.


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## jar546 (Oct 30, 2013)

mjesse said:
			
		

> Agreed. But _*IF*_ the RDP signs off as-is, are they no longer "framing queens"?


No, they are still framing queens and they won't find an RDP to sign off on it because we will ask for their calculations for our records.  That usually puts and end to rubber stamping.


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## GBrackins (Oct 30, 2013)

do the rafters on the right continue past the rafters on the left to another ridge?


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## ICE (Oct 30, 2013)

Some of that lumber doesn't look like #2 or better.  I see that radiant barrier isn't used in your area.  Will the vaulted portion accommodate R30 or whatever is the norm for damned cold?


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## Min&Max (Oct 30, 2013)

Without seeing more I do not believe there is a framing problem(jmo). I would like to know how they will maintain the minimum required R-value and ventilation in ceiling/roof assembly.


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## MASSDRIVER (Oct 30, 2013)

What MIGHT work: rafter tie all the way, replace those horizontal ceiling blocks. Purlin strait up off that wall. Shear off the next interior wall for rack control which would keep that short vault from spreading.

Some combo of all that would work. But I'm not an official wet stamper, just conjecture.

Where's my friggin coffee?

Brent


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## GBrackins (Oct 30, 2013)

here ya go Brent


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## ICE (Oct 30, 2013)

GBrackins said:
			
		

> here ya go Brent


I saw this and discovered that the "Like" button is gone.


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## rleibowitz (Oct 30, 2013)

Damn, This is a good code topic...but I could do without all the BS.


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## Jobsaver (Oct 30, 2013)

The roof-ceiling construction chapter of the code is woefully deficient as concerns rafter thrust, or the lack thereof. Some provision should be made in the code for supporting the ridge as a means to negate rafter thrust.

Until that happens, I do not blame anyone for ignoring the letter of this law provided they are addressing its intent. Today's customers want feature laden ceilings made possible with the advances in engineered wood products. Maybe it is time for the code queens to pony up a better, less antiquidated code section.


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## jar546 (Oct 30, 2013)

GBrackins said:
			
		

> do the rafters on the right continue past the rafters on the left to another ridge?


No, to the exterior wall, hence the problem.


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## MASSDRIVER (Oct 30, 2013)

> Damn, This is a good code topic...but I could do without all the BS.


I agree. Ice and Jar screw up threads with too much tangent b.s.

I on the other hand try to keep posts dry, humorless and as uninteresting as possible.

Professional all the way I say.

Brent


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## jar546 (Oct 30, 2013)

Jobsaver said:
			
		

> The roof-ceiling construction chapter of the code is woefully deficient as concerns rafter thrust, or the lack thereof. Some provision should be made in the code for supporting the ridge as a means to negate rafter thrust.Until that happens, I do not blame anyone for ignoring the letter of this law provided they are addressing its intent. Today's customers want feature laden ceilings made possible with the advances in engineered wood products. Maybe it is time for the code queens to pony up a better, less antiquidated code section.


The prescriptive code is for simple, every-day, routine construction without the use of engineered products.  This issue is covered because they could have put in a ridge beam but they chose not to because of their ignorance and now they have a problem.  The problem here is not the code but the lack of knowledge of the framer.  I still cannot get over the fact that with all of the information provided, some still don't see the problem.  WTF?


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## MASSDRIVER (Oct 30, 2013)

Jar, serious question, seriously.

If the high side of the rafters are sitting on an exterior wall, doesn't that emulate a ridge beam? Is this like a half span roof where one wall is higher than the other ?

If that's the case you would not have rafter spread, correct?

Something I'm not seeing?


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## Rider Rick (Oct 30, 2013)

Jeff,

WTF. I don't see a problem.

Approved.

GOOD TO GO!

OK to insulate.


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## RJJ (Oct 30, 2013)

When I first saw the picture I figured it was a self created problem form the builder. No ridge!?? go figure!


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## jar546 (Oct 30, 2013)

MASSDRIVER said:
			
		

> Jar, serious question, seriously. If the high side of the rafters are sitting on an exterior wall, doesn't that emulate a ridge beam? Is this like a half span roof where one wall is higher than the other ?
> 
> If that's the case you would not have rafter spread, correct?
> 
> Something I'm not seeing?


RIDGE BOARD not on a wall.  Open attic space with no ridge beam on this gable roof where they are trying to make a vaulted ceiling out of one half of the 2nd floor for the master bedroom.

Seriously


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## GBrackins (Oct 30, 2013)

so they need a ridge beam for the main ridge. this eliminates rafter thrust on the rafter to the right. The one on the left coming down to the interior wall is merely a shed roof holding drywall board and needs nothing more (other than considering load on interior wall, or am I missing something?


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## Sifu (Oct 30, 2013)

It seems to me the woefully silent section on roof framing does address this....though not much else.  It prescribes rafter ties or ridge support ( in the form of a beam or wall).  I do see a problem with this framing from a prescriptive point of view and would be a little shocked if even a rubber stamper would let it ride.  BTW I don't think purlins are designed to reduce rafter thrust though I have seen some RDP's give them some credit for it.  As far as the empirical design thing, I agree to a point with that sometimes.  But not for this, the code gives us a minimum standard, in the case of roof framing, very little information leading to a very minimal minimum standard.  I would let the RDP handle it all day long.


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## MASSDRIVER (Oct 30, 2013)

jar546 said:
			
		

> RIDGE BOARD not on a wall.  Open attic space with no ridge beam on this gable roof where they are trying to make a vaulted ceiling out of one half of the 2nd floor for the master bedroom.Seriously


Seriously?

That's no bueno.

Brent


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## jar546 (Oct 30, 2013)

The sad part is that I am more than sure there are some inspectors who would have passed this


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## Min&Max (Oct 30, 2013)

The photo is not showing any ridge board at all but I would suspect there is one up the roof to the left. Depending on how the rest of the roof is constructed a ridge for the vaulted ceiling alone may not be needed for structural integrity. The vaulted ceiling should have less slope than the roof so as to provide space for insulation and ventilation---in which case the vaulted ceiling would need a ridge board.


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## mjesse (Oct 30, 2013)

jar546 said:
			
		

> The sad part is that I am more than sure there are some inspectors who would have passed this


...and even still, the building may just stand for 100 years without issue.


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## GBrackins (Oct 30, 2013)

and I have a bunch of them built back in the early 1700's still standing. Should have seen the fights we had when we went to the 110 mph Basic Wind Speed a few years ago, especially with all the older building that had gone through every major hurricane and were still standing. However, codes are codes.


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## mjesse (Oct 30, 2013)

GBrackins said:
			
		

> However, codes are codes.


Yep, and I agree RDP is required since it's not prescriptive.


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## Min&Max (Oct 30, 2013)

Yeah sounds great to just have a RDP do his/her thing but not everyone has one across the street-----or even within 100 miles.


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## GBrackins (Oct 30, 2013)

so true, but you can prescriptively design a ridge beam by using the Wood Frame Construction Manual. of course if you have more than 70 psf snow load you're out of luck.


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## DRP (Oct 30, 2013)

For something like this the engineering from the lvl supplier has generally been acceptable.

 "I've been doing it this way for X years"... also known as a class action


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## jar546 (Oct 30, 2013)

DRP said:
			
		

> For something like this the engineering from the lvl supplier has generally been acceptable.  "I've been doing it this way for X years"... also known as a class action


Yes, a cut sheet from the LVL manufacturer would have been fine for a ridge.  Key phrase, "would have" but there is no ridge beam, no LVL and no compliance with the code.  The area is a 40# GSL but we could convert that to a LL in the lower 30's


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## Sifu (Oct 31, 2013)

I have had this battle a hundred times.  Usually end up dropping a ridge beam supported to bearing walls below wherever possible.  Nobody ends up happy.


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## Rider Rick (Nov 1, 2013)

I have never seen any walls blow out that didn't have rafter ties. It just doesn't happen.


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## jar546 (Nov 1, 2013)

Rider Rick said:
			
		

> I have never seen any walls blow out that didn't have rafter ties. It just doesn't happen.


I have multiple times.  Even right after framing when they put the shingles on the roof.  The exterior walls moved almost 1" and the ridge sagged.

We do have a snow load up this way too ya know.


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## TimNY (Nov 1, 2013)

If there is no ridge beam the faux "rafters" extending to the left are inconsequential.  As the title of the post indicates, the issue is rafter thrust.  There are no ceiling joists to counter the outward push of the rafter in the right.

The easy solution would be to create a ridge beam.

Tim


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## Rider Rick (Nov 1, 2013)

jar546 said:
			
		

> I have multiple times.  Even right after framing when they put the shingles on the roof.  The exterior walls moved almost 1" and the ridge sagged.  We do have a snow load up this way too ya know.


Jeff,

I'm just going by what I see, the house I live in has clay tile on a 12 and 12 pitch vaulted roof with no rafter ties or ridge beam.


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## Rio (Nov 1, 2013)

Rider Rick said:
			
		

> Jeff,I'm just going by what I see, the house I live in has clay tile on a 12 and 12 pitch vaulted roof with no rafter ties or ridge beam.


_The steeper the pitch the less the thrust._


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## DRP (Nov 1, 2013)

Several times,

My own house, built when I was in my 20's, has no ties in the 2 story 14' wide section, and no ridgebeam. It has a 4/12 pitch, so for every pound of vertical load it produces 3 pounds of horizontal thrust... the flatter the pitch on a simple gable roof the higher the thrust. In its' 36' length it is divided by a stacked crosswall at 14' and then there is a wall about 1' off the peak that runs for about 12', unstacked, that is a non load bearing wall over the kitchen below. The center ~10' is open. We have had a slightly above design load snow load on it ~30psf. The roof held but did sag a bit and the wall bowed out a bit. I learned something in all that as well. The ridgeboard is a 2x12 and by chance it is spliced over bearings. The building wasn't fooled in the least, my non load bearing wall is indeed a load bearing wall and the floor sagged a bit. There is a designed load path and then there is the real load path. Many, many buildings have this scenario. While you are driving around, look at houses with swayback ridges, then sight down the eave walls, bet you'll start noticing it. They might not be collapsing but they also aren't relying on any designed load path.

A couple of weeks ago while we were talking about rafter thrust in another thread I was talking with a gentleman on another forum who put up pictures of his framing and I saw he had a problem. I brought it to his attention, the roof was not yet sheathed and the weight of the 12/12 rafters alone, with collar ties tight up under the ridge, had pushed the walls out of plumb by over an inch in several days. With a jack and ratchet straps they got it back and installed ties. The weight of sheathing it may well have collapsed it, but who's to say, he would also have been building a flexible diaphragm. The prescriptive code doesn't give much credit for that, but it is also an unblocked diaphragm. The top plates act somewhat as a beam between crosswalls, but it is undesigned, same for the soffits. I'm not opposed to beams at the top plates rather than at the ridge to resist that thrust... if you can take care of the reactions. Relying on these elements without consideration and saying "it doesn't happen" is also riding very deep into your safety belt and not knowing where you are.

I'm presently working on an old log barn that was built by someone who knew what they were doing. At some later point someone who didn't understand came in and removed the tie logs in the center to make one large mow that is easy to work in. It is now 4" wider in the middle up top and shoving out hard. We need to remove and replace the side sheds but, the shed diaphragms are restraining it although they are failing. We have some cable and ratchets and formulated a plan to pull the main structure back together and hold it temporarily this afternoon. I've seen several cases of the plate log rolling or sliding out under that thrust.


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## fatboy (Nov 1, 2013)

Well, in my neck of the woods we get some snow also, and I have seen plenty of structures the the ridge has sagged, the walls have bowed, due to inadequate rafter ties. From what I could see in the pic, they need ties. Maybe it works sometimes, somewhere, but...........code requires ties where there is not a beam supporting the ridge.


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## incognito (Nov 1, 2013)

If the vaulted ceiling joists bearing on the interior wall had not been installed would the beam, that many are advocating, be required to support the actual rafters? Probably not but we really do not know because the picture is not showing enough of the roof construction. There is quite possibly, and probably likely, that a ridge exists at the top of the gable end with additional support for the ridge and roof rafters making the pictured vault little more than drywall backing. We are not being provided with enough info.


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