Replies

1. 
   DanH | Nov 09, 2010 10:06pm | #1

   One way it's used is when hurricane strapping is required and you have, say, a 2-story house.  At the floor level of the 2nd floor you have the top of the lower joist, a header, the rim joist, the plate, and then another joist, a distance of maybe 18 inches or two feet after you take into account the "tails" needed for nailing.  Rather than strap each piece to the one directly adjacent, a long strap can be run from the lower stud to the upper.

1. 
   mick182 | Nov 09, 2010 11:40pm | #2

   Gottcha,I was thinking along those lines.

   So, other than embedding it in fresh concrete for under the sill plate and attaching to walls for new framing, is it necessary to use on one story framing over existing slab? We were talking about this yesterday, and one of the fellas said that it is used by attching to sill plate and then to framing. I siad that didn't seem to make much sense to me as the sill plate is already bolted down, so what purpose would a strap attched to the sill plate accomplish. Am I missing something or is this guy off the mark?

   After discussion yesterday at HD regarding using the simpson strapping, it got me thinking as I will be building a small workshop over existing slab where detached garage used to sit, so thought this might be helpful to know now to plan for the correct strapping if necessary. I've had a hard time finding any info online regarding properly installing straps and tie downs, also what is necessary here in upstate ny.

1. 
   slykarma | Nov 10, 2010 01:29am | #3

   Sometimes anchor bolts aren't enough

   Engineers sometimes require stronger or stiffer connection between foundation and framing than simple embedded anchor bolts can offer. Typical spec is Simpson HDU series holddown anchors. These use threaded rod, either drilled/epoxied into foundation or dedicated threaded pigtail rods cast into foundation. They can also be used between floors, although the flat strap connection you describe is usually sufficient. Usually these HDU anchors are required where strong uplift or racking loads are encountered - high wind zones, uplift-prone building designs, shear walls.

   For a simple single storey building, you will likely be fine with anchor bolts embedded in foundation concrete. Make sure wall sheathing is strongly fastened to studs and all three plates. Use H1 hurricane anchors to tie trusses or rafters to the wall plates and you're well secured against uplift. Every point in the system has to be done correctly. If one is missed or inadequate, that's the weak point. No point in using 3" wide straps to tie wall framing to foundation if the trusses are only held to the plates by a nail or two each.

2. 
   DanH | Nov 10, 2010 07:12am | #4

   Where full hurricane strapping is required, the connection must be maintained from foundation to rafter.  At the foundation level, it's advantageous to use either a strap embedded in the foundation or one trapped under the sill plate to run up accross the rim joist and up to the bottom of the stud -- lets one strap do the work of several.

   Of course, in most parts of the country such extensive strapping isn't required.

1. 
   gfretwell | Nov 11, 2010 12:21pm | #5

   "Of course, in most parts of

   "Of course, in most parts of the country such extensive strapping isn't required."

   That is why any little blow does so much damage to your houses up there. I became a huge fan of the Florida building code after looking at houses after the various storms we have had here and comparing the damage to the little dust devils they call tornados in the north east. 50-60 mile an hour gusts seem to just destroy a northern house (the siding peels off, the shingles are in the wind and carports become twisted scrap aluminum) A properly built Florida house shakes that off without being touched. If you guys see 70-80 MPH winds your roofs come off.

   When they show damage pictures like that from here it is usually a trailer with a lot of unpermitted/uninspected add ons.

   You did see the lack of building codes during Andrew in Homestead. It wasn't the fact that there wasn't any code, it was the lack of inspections. Shortly after that Dade county became Miami Dade and the Miami building officials took over code enforcement out in the hinterlands instead of "Billy Bob", the unemployable nephew of some county politician. We started licensing inspectors shortly after that too.

1. 
   DanH | Nov 11, 2010 08:19pm | #6

   Well, generally the most important thing is to strap the roof.  When a blow comes inland, it's usually of short duration (eg, a tornado that's overhead for 15 seconds), so there's not really time for a house to come apart bit by bit like in a hurricane.  A storm that would merit foundation to roof strapping would be a 1000 year event.

   (And I've no doubt that our house would withstand 50-60 mph gusts, given that it's withstood 100 mph gusts without so much as a shingle knocked loose.)

2. 
   harryv | Nov 11, 2010 11:25pm | #7

   Strapping

   Take a look at the Simpson catalog or website for some examples of strapping uses. The engineer of record calls for which strap goes in what location, usually specifying length and nail quantity and diameter on the plans in this area.  On my current project, we've used three coils of CMST 14 & 16 for floor to floor connectios so far. Lots of TECO nails.

1. 
   mick182 | Nov 12, 2010 02:10am | #8

   Thank you. Simpson did provide dome insight.