I was too picky - InspectionNews

Scott Patterson · #1 (**permalink**) 05-30-2007, 05:22 PM

I had a builder tell me that I was being too picky today. He did not care for me telling him that his crew missed some rafter tie downs and that the nails need to be bent over on the rafter tie downs.

He tried to tell me that it was OK to skip every other rafter and that the nails did not need to be turned down. He said he would fax me the document that says it was OK. That was at 11 AM today, and still no fax.

Jack Feldmann · #2 (**permalink**) 05-30-2007, 05:42 PM

It would be OK for him to skip every other one, if he had put in twice as many as it needed.

James Duffin · #3 (**permalink**) 05-30-2007, 06:03 PM

I looked for the code reference for the tie downs and could not find it. What section are you looking at? Thanks!

Jerry Peck · #4 (**permalink**) 05-30-2007, 07:21 PM

Quote:

Originally Posted by Scott Patterson

and that the nails need to be bent over ...

He tried to tell me ... that the nails did not need to be turned down.

He's wrong on the other part, but not on the above part.

Unless the code "specifically" "requires" bending the nails over (the old South Florida Building Codes did pre-Hurricane Andrew), not only is in "not required", it is not really 'a good idea'.

What *should have been used* are those special 'truss nails' Simpson makes. They are 10d, 12d, or 16d (forgot which), but are *only* 1-1/2" long. That way, the nails do not protrude out through the other side of the truss/rafter, but provide full shear.

Bending the nails over only enlarges the hole through the wood, reducing the overall pull out resistance of the nail.

Sure, a bent over nail is more difficult for us to pull out with a hammer, but 'pull out' is not the main force to be reckoned with here, shear is. Getting back to bending the nails over, though, with the enlarged hole in the wood, there is reduced actual pull out resistance, but there is an added 'nail straightening' resistance. That nail straightening resistance affects us with our little hammers, but when the wind whips up and reaches design event loading, one tug and that nail straightens right out, and now, with the lower pull out resistance of the enlarged hole, the nail pulls right out - long before the nail shear value is reached.

After Hurricane Andrew, must testing and debating was done on this very issue, and the requirement to 'bend the nails over' was dropped from the code, because of the ultimate negative effect it had.

Use the right length nail. That solves the problem.

Too long of a nail with one of those clips does not do harm, but if you had a clip on each side, or a hanger on each side, those nails would go through and push the other clip/hanger loose - happened/happens all the time.

I posted this not too long ago, this is basically the same information.

Jerry Peck · #5 (**permalink**) 05-30-2007, 07:31 PM

Quote:

Originally Posted by James Duffin

I looked for the code reference for the tie downs and could not find it. What section are you looking at? Thanks!

From the IRC. (bold is mine)
- R802.11 Roof tie-down.
- - R802.11.1 Uplift resistance.

Roof assemblies which are subject to wind uplift pressures of 20 pounds per square foot (960 Pa) or greater shall have roof rafters or trusses attached to their supporting wall assemblies by connections capable of providing the resistance required in Table R802.11. Wind uplift pressures shall be determined using an effective wind area of 100 square feet (9.3 m2) and Zone 1 in Table R301.2(2), as adjusted for height and exposure per Table R301.2(3).
- - - A continuous load path shall be designed to transmit the uplift forces from the rafter or truss ties to the foundation.

"shall have roof rafters or trusses attached to their supporting wall assemblies by connections"

"shall have" ... not just *some*, but *plural*, as in ... "rafterS or trussES" attached ...

James Duffin · #6 (**permalink**) 05-30-2007, 07:47 PM

Thanks Jerry... I saw that reference but nothing about metal ties was mentioned.....when and who decides when metal ties are required?

Jerry Peck · #7 (**permalink**) 05-30-2007, 07:54 PM

James,

Quote:

Originally Posted by Jerry Peck

- - R802.11.1 Uplift resistance. Roof assemblies which are subject to wind uplift pressures of 20 pounds per square foot (960 Pa) or greater shall have roof rafters or trusses attached to their supporting wall assemblies by connections capable of providing the resistance required in Table R802.11. Wind uplift pressures shall be determined using an effective wind area of 100 square feet (9.3 m2) and Zone 1 in Table R301.2(2), as adjusted for height and exposure per Table R301.2(3).

Usually, the design professional of record/architect/engineer.

James Duffin · #8 (**permalink**) 05-31-2007, 04:12 AM

So the house plans would be the document the builder would use for his documentation it seems?

Scott Patterson · #9 (**permalink**) 05-31-2007, 08:37 AM

Jerry, Thanks for updating me(us) on the nails.

Jerry McCarthy · #10 (**permalink**) 05-31-2007, 10:11 AM

Hi Scott,
Per J.P.: “those special 'truss nails' Simpson makes. They are 10d, 12d, or 16d (forgot which), but are *only* 1-1/2" long.” YES, joist-hanger nails, which are only 1-1/2” in length, should be employed for those rafter clips. Also, the rafter depth to thickness ratio looks like blocking should have been installed?
IRC – 2006:
R802.8 Lateral support. Rafters and ceiling joists having a depth-to-thickness ratio exceeding 5 to 1 based on nominal dimensions shall be provided with lateral support at points of bearing to prevent rotation.
R802.8.1Bridging. Rafters and ceiling joists having a depth to thickness ratio exceeding 6 to 1 based on nominal dimensions shall be supported laterally by solid blocking, diagonal bridging (wood or metal) or a continuous 1-inch by 3-inch (25 mm by 76 mm) wood strip nailed across the rafters or ceiling joists at intervals not exceeding 8 feet (2438 mm).

I also suspect the plate notching of the rafter may exceed 1/6 of the rafter depth?
R802.7.1 Sawn lumber: Notches in solid lumber joists, rafters and beams shall not exceed one-sixth of the depth of the member, shall not be longer than one-third of the depth of the member and shall not be located in the middle one-third of the span. Notches at the ends of the member shall not exceed one-fourth the depth of the member. The tension side of members 4 inches (102 mm) or greater in nominal thickness shall not be notched except at the ends of the members. The diameter of the holes bored or cut into members shall not exceed one-third the depth of the member. Holes shall not be closer than 2 inches (51 mm) to the top or bottom of the member, or to any other hole located in the member. Where the member is also notched, the hole shall not be closer than 2 inches (51 mm) to the notch.
Exception: Notches on cantilevered portions of rafters are permitted provided the dimension of the remaining portion of the rafter is not less than 4-inch nominal (102 mm) and the length of the cantilever does not exceed 24
inches (610 mm).