When it comes to the roof of your home, the inherent strength and ability to withstand adverse weather conditions lies in the weakest link. One often thinks of the structural integrity of a roof in terms of its ability to withstand the downward forces of snow loads.
The upwards force exerted by strong winds, however, can be far more damaging to the roof of a building, and it can potentially cause enormous damage to neighboring properties as well. This is where hurricane roof straps come in.
Hurricane roof straps (or clips) are steel connectors which attach the roof of the building to the wall structure. This creates a complete load path between the roof and the foundations, allowing the force of strong winds to be shared throughout the structure instead of being withstood by only the roof.
While not necessarily commonplace in older homes in the US, hurricane straps are often a compulsory feature in newly built homes in hurricane-prone areas such as Florida, Louisiana, coastal South Eastern USA, and certain midwestern areas that are prone to tornado risks.
What is a Hurricane Roof Strap?
Hurricane roof straps are also known as hurricane ties, hurricane brackets, hurricane anchors, hurricane clips, and hurricane strips. Whichever name they are called by, and whichever form they are found in, hurricane roof straps are extremely important features in a roof.
The metal hurricane strap itself simply connects each rafter or beam to the wall plate or the wall structure. During any sort of windstorm, it is the phenomenon of uplift which needs to be considered, and this is where rooves can be extremely vulnerable. Wind, which acts in the opposite direction to forces such as snow loads, can cause the roof to detach from the building structure.
Due to this, the connection between roof and building structure becomes extremely important, as this connection can take enormous strain during adverse wind conditions such as hurricanes and tornadoes.
A hurricane roof strap is usually made of galvanized steel or stainless steel, and it essentially attaches the roof structure to the wall structure. Because the wall structure is naturally connected to the foundations, this creates a complete load path.
What this means, essentially, is that the forces of the wind are transferred downwards from the roof to the foundation. As a result, the entire structure is able to withstand the load of the wind, which puts pressure on the roof in an upward direction.
So, if the roof is properly secured, it should be able to fully withstand the forces of hurricane winds due to the strong connection which allows the load to be shared by the walls and the foundation.
This means that the roof structure is less likely to blow off and cause further damage to neighboring properties. Hurricane roof straps, resultantly, are the best way for a roof to resist upward and lateral forces caused by extreme wind conditions.
How to Install Hurricane Roof Straps with an Existing Roof
Although the majority of newly built homes in hurricane-prone areas are built with hurricane straps, this is not the case in older homes. Hurricane straps were not previously a requirement, but significant wind damage in recent times has resulted in the inclusion of hurricane straps into building regulations.
The installation of hurricane straps in an existing home will greatly improve the ability of the roof and building structure to withstand extreme wind conditions. While this is more difficult to do once construction is complete, it is indeed possible.
In order to install hurricane straps on an existing roof, the soffit first needs to be removed. Once this has been removed, it is possible to gain access to the parts of the structure needed to install the hurricane roof straps.
In order to remove the soffit, slide it to the end of the eaves, and remove the individual pieces. At each intersection of wall and rafter, the hurricane straps need to be installed. The metal roof straps all have numerous holes, and it is important that nails are secured in each of these holes in order to ensure a proper, secure connection which also lives up to building codes.
The use of the correct type of nail is also extremely important, as the incorrect type of nail will not be up to the correct standard. The nails should be galvanized, and at least 1 ½ inches in length. The reason for this type of nail is that it provides more grip, meaning that they will be less likely to move or be ripped out.
Next, the soffit needs to be replaced. Hopefully, none of the pieces were damaged, which means that you will be able to re-use all of your soffit pieces.
Naturally, the addition of hurricane straps is much more easily achieved during construction or when replacing a roof, but it can still be achieved with relative ease after construction is completed.
What to Consider When Choosing Hurricane Roof Straps
There are several types of hurricane roof straps which are available, and while they all primarily serve the same purpose, they are all made differently, and some are designed for more specific purposes.
When it comes to existing roofs, the multipurpose or timber hurricane straps are the most ideal choice. This is because they are designed to be used in a variety of different applications.
The number of hurricane roof straps needed for your house depends entirely on the number of intersections where rafters and trusses meet the wall studs. For the most secure installation possible, hurricane straps should be installed at each of these intersections.
In order to determine the correct type of hurricane tie for your project, you first need to determine the demand load.
The uplift of both the trusses and the hurricane ties has to be considered, and naturally you shouldn’t use hurricane ties with a capacity less than that of the trusses.
It is of course possible to use multiple connectors, but it’s important to remember that using, for example, 4 hurricane ties does not mean that you will necessarily achieve 4 times the load-bearing capacity.
Many hurricane straps are one-sided fixtures. However, there are others which are designed in such a way as to allow the rafter to fit into a “U” shape design which allows for fastening from both sides of the rafter. If the “U” shape of hurricane strap is being used, then it is important to ensure that the rafter or truss width is suitable to be able to fit into the hurricane tie. The height of the hurricane tie and the wooden members is also another major consideration.
The size of the strap must be compatible with the size of the timber members to ensure that they can be securely attached to one another, ensuring the most secure fit possible.
Types of Hurricane Roof Straps
Because of the different types of roofs in which the straps are used, it is important to find the right type of hurricane strap for your specific project.
Simpson Strong Tie H1 Clip
The Simpson Strong Tie H1 Clip is one of the most commonly used types of hurricane roof strap. Its design allows it to hold the truss or rafter on both sides, and multiple screws (11 per strap) are used to ensure an extremely secure connection.
While mainly designed to prevent uplift of the roof, this type of clip is also able to provide additional reinforcement during times of heavy downward pressure, such as during times of heavy snowfall.
Simpson Strong-Tie H2 Hurricane Tie
The Simpson Strong-Tie H2 Hurricane tie is one which works on only one side of the truss/rafter. This provides a relatively moderate level of protection from the wind. Again, this hurricane tie provides a continuous load path which moves from the roof to the wall plate.
In order to ensure the best resistance to the upward forces of wind, it is important to install these hurricane ties on both sides of the rafter.
H Hurricane Series of Strong Ties
The H Hurricane series of strong ties is made to work with a variety of different rafter and truss styles. The H-16, for example, functions as a strap which wraps around the truss or rafter, as well as under the wall’s top plates.
In the event that it is difficult for other types of straps to reach the top chord, such as when trusses are being used, this type of strap is a very good option.
Internal vs External Installation
There is a major debate as to whether it is best to install hurricane straps internally or externally. Usually, it is best to install them on the exterior of your home in order to ensure the most secure connection possible between roof, walls and foundation.
Correct installation is extremely important, as this ensures the best possible resistance to upwind forces as well as lateral forces, both of which can cause extreme damage to a building. According to building codes, internal and external installation are both acceptable.
There are, however, a number of advantages to installing the ties externally. The biggest of these is to avoid the possibility of wall plate roll. Wall plate roll occurs when the upwards forces created by extreme wind conditions cause the wall plates to lift up and detach from the structure. This, in turn, causes the wall plates to roll towards the exterior of the wall.
When installing hurricane ties on a roof making use of trusses, one has to consider the connector plate between the top chords and bottom chords. This plate can get in the way of a hurricane tie being installed on the interior, so an exterior installation of hurricane ties would be better in this context.
Aesthetics also play an important role in the choice of installation of hurricane ties. If installed internally, hurricane straps may be visible from the inside of the house, and this may not be desirable to you in the context of your home’s interior design.
In some cases, particularly retrofit situations where the hurricane ties are being installed long after construction, an interior installation may simply be the easier option. It is also possible in some cases, where hurricane conditions are extreme, to install ties on both the interior and exterior of the wall.
There is a possibility to enjoy a substantial reduction in your home insurance premiums if you have hurricane roof straps in place in your roof construction. The percentage you save can be anywhere between 20% and 50%. This varies depending on the insurer.
On average, people who upgrade from simple toe-nailing systems to proper hurricane clips/straps are able to save around 37% on their home insurance premiums.
In order to receive this discount, you will have been subject to a thorough inspection of the roof. There are 4 criteria which must be met in order to qualify for the discount, namely:
The rating of your roof’s wind-resistance is based on the weakest connection, and so if the construction does not meet all the above criteria, you will not be eligible to receive the discount, and the connection must be marked as equivalent to toe nailed.
Hurricane Roof Straps Installation Cost
Hurricane straps themselves are not usually expensive items, usually costing between $0.35 and $0.95 each. Naturally the cost will add up quickly considering the number of straps required, and the cost of labor must be considered as well.
Before embarking on the installation of hurricane roof ties, whether on a new-build project or on an existing building, it is important to determine whether the area in which the project is situated is in fact prone to hurricanes or not.
If it is an area in which extreme winds and hurricanes are prevalent, then it is well-worth the effort and expense involved in installing hurricane roof straps, as these will make all the difference during adverse weather conditions.
If, however, there is little risk of major wind damage, then the project can probably be shifted to the bottom of your to-do list.