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Wrong rafter hanger used in framing - thoughts?
2

Wrong rafter hanger used in framing - thoughts?

Wrong rafter hanger used in framing - thoughts?

(OP)
Good morning all,

I am pretty sure I know how I will be responding to this, but was wondering if anyone has ever seen such a blatant misuse of a simpson hanger? The Building Official requested that an engineer look at a lvl 'ridge  beam' as the supplier would not stamp it (i was already going in with eyebrows raised). It turns out that the ridge beam (2-ply 11 3/4" LVL) is okay,  but the rafter hangers are hurricane/earthquake ties (Simpson H1 tie) - not rafter hangers. Snow loads in this area are 55 psf and this simply does not bold well for these 'hangers'. Any thoughts?

Much Appreciated.

RE: Wrong rafter hanger used in framing - thoughts?

Simpson connectors can be used in multiple ways other than what they show in their book.  I don't see anything wrong with it so long as the rafter reaction does not exceed the hanger capacity. Keep in mind the H1 hanger load capacity in the Simpson book is adjusted for wind. So you'll have to factor it down for snow.  

www.idecharlotte.com

RE: Wrong rafter hanger used in framing - thoughts?

Looks like you might have a collar tie arrangement here.  Is that correct?

As for the hangers, I definitely would use a bottom bearing hanger with a top bearing flange too.  Simpson makes some that could be placed over the hangers that are there now, or the hangers could also be removed if they interfere too much.  

Use something similar to the IT hangers for TJI's, but made for the solid joists you have, that can be spread tempoorarily for easier installation.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Wrong rafter hanger used in framing - thoughts?

I see a few issues with this that need to be resolved.

firstly, the nails to the rafter will be too close to the end and will therefore have much less capacity than in the simpson catalogue diagram where it is a continuous rafter.

Secondly, thers is very little top restraint.

Thirdly this is not a very good detail for uplift where there will be tension at this connection.

I would definately look at putting some additional brackets as msquared has suggested though I would think that a couple of angle brackets would do the trick and would be easier to install.

RE: Wrong rafter hanger used in framing - thoughts?

Strange looking framing.  Can you provide an elevation of a typical rafter?

BA

RE: Wrong rafter hanger used in framing - thoughts?

Toe nail each rafter into the ridge beam (10 or 12 per). I know builders who have been in business for decades without ever using a simpson product (just toenails) and have never seen a failure. Not advocating this as general practice, but if the shoe fits, and the ridge pole isn't doing much anyway....

RE: Wrong rafter hanger used in framing - thoughts?

msquared48, has it right I just ssw essentially the same thing being done where the wrong hangers were used.  One second hanger was a Simpson type, the other was a locally fabricated strap type hanger.
The finer older houses here all have heart pine ridge beamw and use a ledger board.  Some rafters have a bird's mouth and some don't. Some of the beams are massive 3 or 4" tk x 12"-16" deep. Most of the larger beams have a collar beam toching the bottom of the ridge beam.

I would give Simpson a call.  The few times I've called they have been quite helpful  
 

RE: Wrong rafter hanger used in framing - thoughts?

Agree with Mike.  It can still be retrofitted.

VTEIT....hopefully you'll never have to testify to that effect.  Toe-nailing is a miserable way to make a shear or tension connection.  The main reason most of them have not failed is because they have never felt the loads for which they were supposed to be designed and constructed to resist, or the structure was not really designed, but built with a great deal of "overdesign".  Test 10 different toe-nailed connections by 10 different carpenters and you'll get 10 significantly different values.

Yes, there are many wood structures with no "engineered" connectors of any type.  Most have more capacity in the seat of the pants overdesign than they'll ever need.  In more recent times, there is a tendency to mix old methods with new designs, which are much more optimized, and the results can be disastrous.

In this case, you have a competent ridge beam with collar ties.  All you need is good rafter connections!

unclesyd is right...Simpson is very helpful.

RE: Wrong rafter hanger used in framing - thoughts?

BA is on to something here. The rafter looks like 2/3 of its depth was cut at the tie location. I would be more concerned with that. I don't think that notch meets code requirements.

RE: Wrong rafter hanger used in framing - thoughts?

nac,

That is the way it appears to me too.  Looks like the rafter would fail in bending at the tie connection.

BA

RE: Wrong rafter hanger used in framing - thoughts?

If it's a ridge beam, then you don't need collar ties.

Toe nails are perfectly acceptable per NDS. There is a reduction in shear capacity. You should be able to add enough of them to obtain the capacity.

RE: Wrong rafter hanger used in framing - thoughts?

I'm with you Ron, even though others will disagree. I don't care who accepts them, I have never and will never use toe nails. Simpson and the like make such easy to use and cheap connections why bother? And for all of the reasons you gave. Anyone disagree just take a 2x4 scrap and do a few toe nails. Pretty hard aren't they? Try that overhead now. Then sledge-o-matic the end of your connection and tell me how good you feel about signing and sealing these....

RE: Wrong rafter hanger used in framing - thoughts?

take a 2x10 rafter attached to an LVL ridge w/ 5 good toe nails ea. side w/o splintering the rafter. Test load it and see what you have for an ultimate capacity. It will probably be around 1800 lbs in shear. Divide that by a SF of 4 and you should have about a safe load of 400 to 500 lbs.

I agree with the sloped Simpson hangers for unusually long rafters and/ or very high snow load regions. But to specify them all the time is a waste of money and too conservative.

RE: Wrong rafter hanger used in framing - thoughts?

A waste of money? $2 per connection max? I have installed them, they are EASY, couple of minutes especially if you use the Simpson 1-1/2" long nails. And they are not dependent on no splitting which is difficult, so inspection and installation are made quite simple.

But they are allowed, so specify whatever you want if you are comfy with them. I am not... I also am in Florida so we are talking uplift also.

RE: Wrong rafter hanger used in framing - thoughts?

End of beam has no uplift connections
Check beam bearing
No OSB sheathing spacer clips
Missing blocking for drywall
Far side rafters looks like they are 2x4s
Frame out sheathing penetrations (far side)
Consider a strong back for ceiling joists

RE: Wrong rafter hanger used in framing - thoughts?

For anyone who has done convential framing, whether floors or roofs, connector plates make the framing a lot easier.  You need three hands to hold a hip rafter in place and toe nail it.  With connectors you set the hip ridge, set the plates and tie to them...safer, quicker, and easier.  Saving labor saves more money than dropping widgets.

Also keep in mind that the cut angles for roof rafters and other conventional framing allow gravity to work WITH the connection.  Uplift works AGAINST the connection angle, so more load is placed on the fastener.

Nice observations, boo1!

RE: Wrong rafter hanger used in framing - thoughts?

Toe nails are acceptable but definatly not preferred.  However we are in a situation now that I would accept them.  And with nail guns that EVERYONE uses these days, you will get consistancy and it is not that difficult.  

RE: Wrong rafter hanger used in framing - thoughts?

a2mfk -  toenailing isn't difficult. As DWHA said, who frames with a hammer now? Toenailing with a nailgun take TWO hands and is easy. Won't see purely tow-nailed connections on joists or rafters in my house, but this is a good application.
 

RE: Wrong rafter hanger used in framing - thoughts?

I've framed with a nail gun, and yes it makes things easier, but its not automatic. To get the right angle and not cause any splitting, and to do it right to get the shear values you are assuming, can be a bit tricky. Add a ladder and it being overhead, and its an effort...  If we are talking about sloped rafters attaching to a ridge beam, then gravity loads keep these in place anyway, but my concern is also with high uplift reactions.

But as I said before, you are free to specify them since they are allowed. I just never will because I don't buy the cost savings argument over using hangers, especially on the total cost of the framing. That is a good investment in my mind. A framer isn't making six figures and an extra few minutes is no biggie.

RE: Wrong rafter hanger used in framing - thoughts?

From my experience, most framers toe nail first and then go back and put the hangers in if they're specified. This is true for joists and rafters. Hangers just slow them down. They need to get the framing up and weather tight ASAP.

If you have a 5:12 pitch, 2x10 rafters at 16" spanning up to 14' or so, most engineers here would specify sloped hangers? For commercial work I understand, but for residential I think most framers would think you're a little nutty.

When you add the cost for the hanger and additional labor, I think you're talking about $5 each connection - maybe $500 to $600 extra on the average roof of a house. Not a whole lot more, but if you carry this conservatism design approach throughout a decent size home, you could be adding thousands of unnecessary dollars to the cost of the house. I have had long conversations with very experienced framers on these types of things that drive them crazy.

RE: Wrong rafter hanger used in framing - thoughts?

cb1331,
As some have pointed out, it looks like the rafters have been notched above the collar ties.  Why is that?  I would be concerned about that.

RE: Wrong rafter hanger used in framing - thoughts?

(OP)
Thanks for all the responses; some variance on a firm decision on which method is better (toenailing vs. hangers) but hey - welcome to structural engineering.

To clarify, the rafters have not been notched, and are continuous 2x6 rafters from the ridge beam to the supporting walls. Collar ties were strapped to the sides of the rafters with common wire nails (no nail gun). I sketched up a proper hanger detail for him using more preferred methods than hurricane clips as hangers - consequently the supplier provided him with these as hangers (so he says........).

 

RE: Wrong rafter hanger used in framing - thoughts?

cb,
This might be a little off topic but I was wondering what the 2x8's below the 2x6 rafters are all about. If my attached drawing is somewhat accurate (can't see exterior walls), why not just use stronger rafters all the way to the ridge and save labor? I've seen this design used in trusses but never in my years of building stick framed homes, additions etc. I guess I could see it in an upgrade to an existing building but this appears to be new construction. Just curious.

Doug

RE: Wrong rafter hanger used in framing - thoughts?

4thorns,
The additional 2x8 framing, from what I can see in the photo provided, is most likely scabbed on undrframing to allow maximum batt insulation to be installed (probably R-38 batts and allowing for a 1" air space for venting) for the volume ceiling built.  If it was me, I would be checking the adequacy of the rafter span (2x6's) to make sure that they are not overspanned and with all of the underframing applied, sloped and flat (collar ties).  It appears the rafters are 2x6's @ 16" O.C., but I don't think the length of the rafter span was given.  55 psf roof snow load is pretty high.......it does confirm the colder climate application.

I would have liked to see the framed the roof with a larger dimension rafter, forget the scabbed on underframing (because your ceiling wall transition is still at the same height) and treated the whole roof system as a cathedral ceiling, thus rafter span & correct hanger selection for rafter connectors might not be a question?????

Just what I can decifer..........

RE: Wrong rafter hanger used in framing - thoughts?

I agree with jefesdi about the scabbling on for insulation depth, and the fact that the rafters should have been 2X12's in the first place.  

The 2X6's, if not overstressed in bending, will surely deflect down at the collar tie connection under full load allowing the deflection to be read outside in the roofing, and will probably become a permanent deflectior, if the snow load is long term.  Moreover, lateral spreading of the exterior walls may become an issue with interior sheetrock damage seen.

I strongly suspect that a structural was not involved in the design prior to the picture being taken.  Sharp Building Official though in my opinion.   

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Wrong rafter hanger used in framing - thoughts?

Also, with the load given, the position of the collar ties, and since the collar ties are a single shear connection with shallow members, I would check the collar tie connection very closely by running the numbers.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Wrong rafter hanger used in framing - thoughts?

Is it a collar tie or a collar strut?  Under gravity load, it should be in compression.

BA

RE: Wrong rafter hanger used in framing - thoughts?

Depends on whether or not the bearing walls can spread.  

Good point BA, but with residential construction, I would expect tension.

Mike McCann
MMC Engineering
Motto:  KISS
Motivation:  Don't ask

RE: Wrong rafter hanger used in framing - thoughts?

If the roof ridge beam has beem "sized properly" acording to the start of this thread (with a low vertical deflection limit for this cathedral ceiling setup), then the collar tie would be in tension due to the fact that the top of the exterior walls are not restrained (which I assume is the case).  That is why the connection at the ridge beam is so important in this instance.  I don't know if the inspector even realized that the connection at the ridge could be in tension as well with an unbalanced snow drift.  It might very well turn out that the rafters are undersized for loading & deflection, and that sistering new rafter members next to the existing will necessitate new (replacement) connectors at the roof ridge beam.  Especially for limiting drywall cracking as msquared48 pointed out above, I would be concerned.......

RE: Wrong rafter hanger used in framing - thoughts?

Whether it is a collar tie or a collar strut is an indeterminate problem which depends on the rafter location and the relative stiffnesses of ridge beam and rafter.

Collar ties located near the end of the ridge beam will tend to compress with snow load because the ridge beam deflection is minimal and the rafter deflection is normal to the roof slope.

BA

RE: Wrong rafter hanger used in framing - thoughts?

Just for curosity, I noticed that the rafter just left of center has a fairly large wane that goes into the connector.  In our area this large of a wane is not permitted.  The rafters to the right also appear to be older wood, not the pretty "white wood" again not permitted if the lumber has been in service. You have to cut out the previously nailed portion before you sneak it by.

have you contacted Simpson yet?   

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