- Strengthen the attachment of the roof sheathing to the roof framing.
- Strengthen or replace roof vents.
- Do what you can to improve the wind resistance of yoru existing roof cover.
The following provide more information on alternatives for completing these basic steps.
Strengthen the Roof Sheathing Attachment
The most cost effective way to permanently improve the fastening of roof sheathing to the roof structure is to add fasteners when the roof cover is being replaced. However, if your roof cover is reasonably new or in good condition and you are not going to re-roof soon, you should check the types of fasteners and their spacing to determine whether the connection is weak. A weak connection would make your sheathing vulnerable to being lifted off by hurricane induced uplift pressures on the roof. When plywood sheathing was first introduced in the 1970’s building codes allowed the sheathing to be installed with 6d nails. The nails were to be no more than 6-inches apart along the 4-foot edges of the sheets (edges) and 12-inches apart along the intermediate framing members (the field). This spacing was driven by shear requirements with little regard to roof uplift pressures. These requirements continued throughout most of the hurricane prone regions until the widespread damage from Hurricane Andrew clearly showed that this nailing pattern was inadequate in hurricane prone regions. There has also been widespread use of staples to attach the roof sheathing. This was allowed by the Standard Building Code (the code that was used, if any was required, throughout most of the Southeastern US) until 1998. Testing has demonstrated that neither of these methods of fastening performs well when the sheathing is subjected to the wind uplift pressures that are produced by even a moderate hurricane. The testing conducted following hurricane Andrew also indicated that the most critical spacing of fasteners was that of the nails in the field where a larger spacing was historically allowed.
Loss of even one piece of roof sheathing can result in internal damage to your home and contents that is nearly ten times the cost of the damage to the exterior of your home. Consequently, one of the things you need to do is to determine what kind, size and spacing of fasteners (nails or staples) is used to attach the roof deck to the trusses or rafters. The greatest risk of losing roof sheathing is on houses with gable ends where the sheathing has been attached with 6d nails or staples. Inspecting – Checking the attachment of your sheathing to the framing
Tools you will need:
- Tape measure
- Thin ruler or a piece of heavy paper
- Stud Finder with metal detector capability
- A marker
- Light (You can work with a flashlight but a light that can be clipped onto a framing member and aimed where you want would be better.)
What to do:
- Bring out the Roof Sheathing Evaluation Checklist.
- Look for a label on the sheathing indicating its thickness and rating. If you can’t find a printed label, look for an exposed edge of the sheathing where you can measure the thickness of the sheathing. If you can’t find an edge that you can get to, find a joint between two of the roof sheathing members and stick the heavy paper or thin ruler into the crack until it touched the roof covering. Don’t push too hard with the ruler as you may damage the roof cover.
Call Amherst Roofing of Collier County, FL for a Free Estimate at 239-594-1133.