Voices on the Wind

With the cool change passing over (which brings with it strong, gusting winds), I am reminded of a day many years ago now where the winds arrived and quickly made such a mark on my shed at the time.

Back in 2002 or so, (things are getting particularly hazy), I needed more space than the 3m x 3m shed I was using was offering.  An old Mercedes that I had was sold, and that financed a new 6m x 3m shed by Spanbilt.  It was an amazing thing, having so much more space than I had been coping with.

This was also as my Triton collection was undergoing a rapid expansion, and the Dingo that had joined the family needed a home.  You may have seen the resulting dog house, either on here or in a magazine (House and Home I think).  It was a heavy thing, with cyprus pine weatherboards all made on the Triton Workcentre.  It has particular relevance to this story.

One wet day, the wind was really gusting in, and I had headed out to the shed to see how it was going.  It was therefore particularly concerning when I saw the roof flexing dramatically above one of the doors.  The wind passing over was really lifting the roof at one point, so I started hanging on, while trying to reach  hammer, nails, screws or whatever might help stabilise the roof.

Watching the building closely (while literally hanging off it), I could see a real defect in the design around the door frames.  The roof was lifting right above the corners of the doors.  So while using my bodyweight to hang onto the roof above one door, the wind began ripping sheet after sheet off above the other.  Not only was the roof flying off, over the neighbour’s fence, but even the wall sheets and door were following.  If it wasn’t for the Triton Woodrack on the back wall heavily loaded, I have no doubt the whole half of the shed would have gone.  Even so, the damage was dramatic.  It was still raining, and all the tools that had suddenly been exposed to the elements were getting a soaking.

With a trip to the local box hardware store for a big groundsheet, the effort was in getting it across the roof, and secured against any additional winds.  This is where the newly built doghouse came in – with the decent weight it was placed on one side of the groundsheet to hold it down.

The shed repair was something else, with many panels bent, and some beyond easy redemption.  A call to Spanbilt yielded no joy – they claimed the sheds were more than suitable for Melbourne’s weather conditions, and not only were they not prepared to supply any panels to replace the damaged ones, they were not interested in doing so even where I was wanting to pay for them.

So instead, I sourced some treated pine and built a sub-frame that the tin was to be attached to .  Heavily bent panels were hammered flat an nailed to the new frame.  This design became the basis for the current 8m x 4m shed, and that has not moved an inch, even in particularly strong winds.

So that is the end of the tale, and the visual I still have when the winds get a bit fresh.  Seeing panel after panel flying across the fence – I can’t imagine what it is like for those in the States in the tornado alley, watching whole houses vanish in a puff of wind.

These days, with the shed built with the lessons of the past incorporated in the design and construction, let it blow – I can go back to enjoying listening to the wind and rain throw its fury at my place, content in the knowledge that the shed (and the tools therein) will be there, safe and intact day after day, storm after storm.

Securing a Shed

I had an interesting question posed via email about how to hold down a shed, particularly in high weather affected areas.

To qualify, I am not a structural, or civil engineer, so these are just my thoughts on the issue, so take them in that regard.

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As I see it, there is one primary failure method for a structure subjected to high wind, and that is for the roof to lift (whether or not it also lifts the walls with it!)  A roof, like any flat or convex curved surface causes a pressure differential when air blows over it, creating lift.  When the lift exceeds the strength of the fasteners (either locally or in total), the roof fails, and as does the structure.

The local building codes will hopefully have some guidelines, particularly on wind strengths to consider.

If you can secure the roof down sufficiently (and consider that the heavier the roof, the stronger a wind would be required to lift it), then the whole structure can be considered one element, and the problem becomes a lot easier.  Then you need enough bolts (I typically use dynabolts from Ramset into concrete, which have a high pull-out load (ie how much force needed to rip them out of the slab)).  If you REALLY want to get technical, this pdf product sheet gives you the calculations for working out just what a bolt can take, based on what material it is afixed into.

As a basic rule-of-thumb, I’d place a dynabolt in every 1.5m or so, with a minimum of 3 per wall (one in each corner, one in the centre).  Probably overkill, but the bolts are cheap, and a lot cheaper than watching your shed become the next door neighbour’s shed curtesy of a wind gust!

So the shed is secured down, and anything you add to the weight of the structure will also help – a full woodrack works wonders (yes, speaking from experience here!).

So back to the roof then – the real source of weakness.  A heavily constructed roof will survive a lot better than one that clips (or worse, rests) together.  So if you have one made from sections of tin that simply rest one on the next, and clip in top and bottom, you are destined for some heartache.  If you improve the structure so the roof is one unit (rather than a bunch of panels), things rapidly improve.  It can be as simple as steel rivets, so you end up with one large panel for a roof.  That way, if an individual joint or connection fails (such as round a doorway), the entire roof still has to be lifted, and not the individual panel. (Did I mention I really don’t like clip-together sheds?  At least not without some aftermarket modifications!)  If you want examples of what I mean, just watch any video footage of a hurricane.  What do you see blowing around?  Lengths of corrugated iron.  If you see an entire roof going, then we are dealing with something else (tornado!)  Corrugated iron is normally screwed to the structure individually, so if the few screws holding one panel down fail, that section blows off, exposing the rest of the structure to the full force of the wind, and more panels will often follow.  If the corrugated iron was joined together, separately to being fixed down it would be a lot stronger.

The final thing I’ll touch on is banding.  Guyropes (if you are into camping), which are used to hold a tent down.  Where wind is a real factor, throwing a rope over the top of the structure and securing it down significantly improves its survivability, and the same holds true for a shed.  A metal band or two over the top of the structure will significantly improve the connection between the roof and the walls, and effectively increases the overall weight of the shed.  These can be dynabolted directly to the slab.

So those are my thoughts on the subject.  I’m sure there are plenty of books on the subject somewhere!  Hopefully, they don’t contradict the-above thoughts!

A Storm is Coming

My phone told me so.

This will be the first real test of my shed-constructing ability – wind, real wind. Starting sometime tonight Victoria is meant to be hit with strong winds, up to 150km/hr gusts which we are being warned will produce conditions not dissimilar to those of a couple of weeks ago, resulting in the worst bushfires in recorded Australian history.

The Victorian government have even taken an unprecedented step of SMSing everyone in the State (except those on a couple of cellular networks – not sure what caused that hole in the coverage). (And an excellent application of modern tech too, so long as it is not over-utilised).

So it is batten down the hatches, secure all FOD, and hurry up and wait. Very eerie.

Update- morning has arrived, and boy, what a howler. Oh wait, what’s the oposite of a howler? Deathy still?

The wind must have gotten held up in traffic. Not like the weather office to get the timing of atmospheric events wrong. Oh wait (again). It must be opposites day!

I’m sure bad things are still coming though, just a little delayed.

My phone told me so.

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