You will have to consult the local building codes department for the county. The should have a handout. Your architect and builder should have copies of the building code and its requirements. There a tremendous difference in the requirements in the state of Florida, though they are coming closer. I think Dade county has the most stringent codes as to hurricane ties.
If it were my home. I'd pay to have the extra ties put in and meet whatever is the most stringent requirement in the state. Really. Aside from peace of mind, you can advertise the presence of extra ties when you sell the home. Just be sure to document them.
You might get an insurance discount, too. (But don't hold your breath...)
Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.
There are alot of factors that determine this, but lets say you have a house with the following criteria
Lateral Framing Connection Loads from Wind
for Roof to Plate, Plate to Stud, and Plate to Floor
Wind Speed- 3 second gust: 150 mph
(This is the most wind force used for the most severe locations. You need to determine what's required in your area)
Wall Height: 10 ft
Unit Framing Loads: 246 pounds per linear foot
Now you have to select a hurricane anchor that takes this force. Normally you place an anchor at every rafter (spaced at 16 inches on center).
Thus 16/12 x 246 = 328 lbs is the strength of the hurricance anchor you select.
So, its not only how many anchors to put on, but what strength the anchors can take.
I live not to far North of you up I-95. Florida requires house plans to be signed and sealed by Professional Engineer. This came into effect after Andrew. Also the house must be designed to the subscribed wind speeds for your locale.
I am not sure which hurricane ties you are talking about? It depends on the constructions of the house. If it is Masonry and pre-engineered wood trusses (this is one of the most common methods in Florida), then all you need to worry about is the truss tied down to the wall. Make sure that your truss tie down is selected not to only resist uplift; but it must be able to carry wind loads that are perpendicular and parallel to the masonry wall. Truss spacing will dictate the truss tie down location and frequency.
The masonry wall is to have vertical and horizontal reinforcement as stipulated by your engineer and code to resist the wind loads on the wall (loads that are perpendicular to the wall and hear loads from shear walls). The vertical reinforcement should be continuous from the foundations all the way up to the tie beams (bond beams).
The other type of construction is framed construction. This one is tricky! You must ensure a continuous load path all the way from the room to the foundations. You will be required to provide hurricane ties and straps at such locations as follows:
1. Truss tie down
2. Top plate connection to the vertical wall stud.
3. Vertical wall stud tie to the bottom plate
4. Bottom plate to the foundation
5. Similar ties all around the windows, doors and other openings.
6. Wall ABs to the foundation for shear transfer (as required by shear wall design).
7. Other areas that I left out!!!!!!
As you can see, there is no simple answer to your question. I personally do not provide engineering for residential structure (unless they are significant in size) because contractors and owner do not want to pay the reasonable fee to do proper job.
I would like also to comment on the fact that as a homeowner, normally, no one is out at the site to protect your interest. The contractor is looking for his own benefits. The county or city inspector is looking for few and certain things during his inspection. That is why so many problems and mistakes go un-noticed and wind up costing the homeowner in days to come.
Let me know if you have any more questions. Good luck.
lutfi,
There is an interesting development in the home building up in the north of Florida. They are tying the truss to frame connection to the slab by using all-thread from either the embedded anchor or they are using epoxy and tying the all- thread with a clip to the truss. I haven't seen any details yet. My fishing buddy sells all-thread and is very happy.
According to the FBC 2001 you are in 140 MPH hurricane According to the FBC 2001 you are in a 140 MPH zone. Find out what your local building department wants you to use.
Get an engineer to check the wind forces on your roof and walls. Put a tiedown on each truss and choose the number of nails that fits the load need. Your county may want common catalogue tie downs or Dade County approved ones. The catalogue load capacity can be different from Dade county's approved capacity. Follow the FBC 2001 for loads in chapter 16 and the height of the building.
If you really care about your house, do not spare the cost of an engineer or wise architect. There will be less problems during construction.
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