Wrong rafter hanger used in framing - thoughts? 2

[cb1331]

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.

 

[idecharlotte]

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.

http://www.idecharlotte.com

 

[msquared48]

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

 

[csd72]

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.

 

[BAretired]

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

BA

 

[HeavyCivil]

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....

 

[unclesyd]

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

 

[Ron]

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.

 

[nac521]

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.

 

[BAretired]

nac,

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

BA

 

[UnthoughtKnown]

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.

 

[a2mfk]

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....

 

[UnthoughtKnown]

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.

 

[a2mfk]

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.

 

[boo1]

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

 

[Ron]

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!

 

[DWHA]

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.

 

[HeavyCivil]

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.

 

[a2mfk]

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.

 

[UnthoughtKnown]

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.