A quick 'how-to' guide for monitoring snow load on the roof of a temporary demountable structure: for marquee hire companies
Knowing what you are looking for, in the way of 'tell-tale signs' of your temporary building being placed under duress, being weighed down under snow on the roof can be the difference between safety and structural failure.
Performing thorough 'before, during and after' marquee inspections will uncover the warning signs, if any, during a snow event, of roof overloading.
Your familiarity with how your marquee structure ought to look and behave under normal conditions, will grant you the 'eyes' to see any changes which might be compromising the integrity your tent.
From the baseline snapshot of the 'as-is' picture on delivery, following your handover inspection, plus your knowledge of the structural characteristics and framing system of the marquee you will know if remedial attention is required as relating to snow load on any given occasion.
The following are key aspects of consideration for the monitoring of marquee roof snow load:
- Structural snow load estimations
- every manufacturer will include some estimation of snow load tolerance within their design specification
- Framing system
- understanding of how the marquee system fixes together and therefore where the vulnerabilities will lie is key to determining the level of snow load risk
What are the key areas of inspection with snow load?
Of course, the roof areas are the places where snow load will be borne by your marquee structure. But typically, you can find the geometric factors which contribute to structural vulnerability being very similar, no matter the structure.
Some high risk areas for snow load which you'll want to inspect as priority, might be:
- Stretches of canopy just above the eaves at the lowest point of the roof slope
- these bear the most weight as the snow load from higher points pile in here which can cause bulging
- Roof valleys where you have assembled structures side by side
- where snow collects and converges from both sides of the slope, the proportionate load in such areas is greatly increased
So what are we looking out for as signs that our marquee might be in need of some help with bearing it's snow load?
The warnings may initially be unremarkable at first glance, but as with all risk: the earlier you identify it, the more time you have to tackle it and the potential for damage is greatly reduced.
Deterioration: where integrity of the structure is compromised and not like it should be, this would indicate your snow load poses risk
Weakness: where components should hold fast, there seems to be a laxity which is uncharacteristic with that type of installation
Damage: where there is frank structural deformity or damage this would indicate urgency is needed to save potential personal injury or loss
What are signs of overstress with regard to marquee snow load on roof?
If you have any of the points below whilst monitoring your marquee during heavy snow events, then it is likely your structure is overstressed by snow load:
- Roof sagging
- marquee fabric between roof beams, particularly just above the eaves sags showing significant overhead load and risk
- bent or deformed structural straights, whether horizontal or vertical, during snow load event would indicate your marquee is under considerable stress and in need of an emergency rescue
- unusual creaking, popping or cracking sounds during a snow event may indicate snow load stress has gone beyond safe parameters
- Roof leaks
- the temperature difference between the inside of the marquee (if heated) and the outdoors during a snow event can be quite a contrast. Snow on roof can melt in parts and if snow load is overstressing the structure, the resulting water may be observed leaking into the tent (at weakened seams) where deterioration has occurred.
- Doors struggle to be opened and closed
- ground snow levels which occlude entrances and exits would give an indication that roof snow load is in need of close inspection. Ground snow and roof snow load are entirely different in character, though it certainly should alert you if ground snow depth is affecting the functioning of other aspects of the marquee.
Anything to add? Feel free to comment below.
Categorised in: A Guide To Event Health and Safety
This post was written by selmore