{"id":311179,"date":"2021-07-29T16:42:12","date_gmt":"2021-07-29T13:42:12","guid":{"rendered":"https:\/\/en.buradabiliyorum.com\/hurricane-straps-keep-roofs-on-houses-and-can-improve-safety-during-tornadoes\/"},"modified":"2021-07-29T16:42:12","modified_gmt":"2021-07-29T13:42:12","slug":"hurricane-straps-keep-roofs-on-houses-and-can-improve-safety-during-tornadoes","status":"publish","type":"post","link":"https:\/\/buradabiliyorum.com\/en\/hurricane-straps-keep-roofs-on-houses-and-can-improve-safety-during-tornadoes\/","title":{"rendered":"#Hurricane straps keep roofs on houses and can improve safety during tornadoes"},"content":{"rendered":"

“#Hurricane straps keep roofs on houses and can improve safety during tornadoes<\/strong>”<\/p>\n

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\n Some of the worst damage from the EF-2 tornado that struck the Ontario city of Barrie on July 15. Credit: Northern Tornadoes Project, Author provided
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Many people think of a well-built house as one where the walls are strong enough to hold up the roof so it won’t fall on them. This is reinforced by children’s stories like the Three Little Pigs<\/a>, where the house made of brick is the strongest when the Big Bad Wolf comes to town.<\/p>\n

When a strong tornado passes through a neighborhood, it results in total chaos. Debris is everywhere. Shingles and siding and bricks are thrown about. Entire roofs are tossed, often landing on neighboring homes. Walls collapse, cars are rolled and flipped. Insulation is stuck to every surface like a strange snowfall. <\/p>\n

On July 15, a tornado struck Barrie, Ont., destroying several homes: Could anything have been done to minimize the damage in Barrie?<\/p>\n

Holding on to the roof<\/b><\/p>\n

In any windstorm, tornadoes included, the roof needs to be secured\u2014this is due to the uplift, the same physics that allows an aircraft to fly. This runs counter to our intuition since we tend to think about roofs collapsing, not flying. The uplift is the main vulnerability of houses. The structure of residential roofs in Canada tend to be strong because they are designed to handle the heavy weight of snow in winter. <\/p>\n

For the wind, which acts in the opposite direction as the snow, it is the nails connecting the trusses to the top of the wall that become critical to ensure that the roof stays in place during a severe storm.<\/p>\n

The National Building Code of Canada requires three nails\u2014just over three inches long\u2014in each roof-to-wall connection<\/a>. These toe nails, as they are called, are what hold the roof down in the wind. If this is done properly, the roof structure should be safe until wind speeds reach about 160 kilometers an hour<\/a>. At such wind speeds, asphalt shingles may blow off but the roof structure will remain intact.<\/p>\n

Houses are not designed for tornadoes, although the building code discusses tornadoes. The requirements for fastening the walls to the foundations were developed to deal with tornadoes. These were included in the 1995 release of the National Building Code following tragic deaths in 1984 when cottages were swept into Blue Sea Lake in Qu\u00e9bec<\/a>, along with post-storm observations following a 1985 tornado in Barrie<\/a>.
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It is now known that toe-nailed connections are the weak links in the structure, more likely to fail before the roof sheathing<\/a> and before the walls pull apart from the foundation. Walls are more likely to collapse when the roof is gone, and the roof itself can become airborne. Both of these are threats to life and safety.<\/p>\n

The Northern Tornadoes Project<\/a> survey in the immedia<\/a>te aftermath of the recent tornado in Barrie indicated that several homes did not meet the building code requirements because of missing toe nails. <\/p>\n

This is nothing new. <\/p>\n

Similar observations were made in 2009, when tornadoes landed in Vaughan<\/a>, and in 2014 in Angus<\/a>.<\/p>\n


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