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Emergency Snow Loads - Are you Prepared?

Emergency Snow Loads – Are You Prepared?

You’ve seen it played out in cinema time and time again.  A snowstorm comes and people argue over who’s going to clear it. 
What?  You don’t remember seeing that in any movies?  Really?  Well, take this classic scene from “A Few Good Men” for instance:

Colonel Jessup:  “You want to clean outside?”
Lt. Kaffee:  “I want the roof!”
Colonel Jessup:  “You can’t handle the roof!!”


Fine, maybe that’s not quite how the line goes, but close enough.  The point is, I’m sure that whenever there’s a heavy snowfall around the world, there are similar conversations occurring (though, probably arguing to be the one to NOT have to go on the roof).  The infrequency of snowfall in some areas, and the unpredictable nature of it, lead most people to not think about snow and its effects until it happens.  Who thinks about being buried in mounds of snow in the heat of summer?  Who worries about snow loads when the most you usually get is just a few inches?  The answer: very few people.  In fact, up until 2013, while FEMA had contingency plans for flooding and earthquakes, there was no such document related to snow and its roof loading.

In reality, the vast majority of the time, a roof won’t be affected by snow and attempting to clear the snow will be a much greater hazard than just waiting for it to melt on its own.  However, that’s not always the case and during the recent blizzard in the northeast, a number of buildings lost their roofs due to snow, including a church in Downingtown, PA, part of the roof of a sports complex in Rahway, NJ and a Trader Joe’s in Westfield, NJ.  It is much better to be prepared than to suffer such property damage (which, of course, also puts people in harm’s way – whether it be patrons of the facility if they haven’t been kept away by the storm or the people scrambling to clear the snow before it’s too late).  Perhaps it’s not often that that type of snowfall occurs in the area, but as Mrs. Gump told her son:

Forrest Gump:
“Mama always said snow was like a box of chocolates.  You never know what you’re gonna get.”

Know What You're Working With

To begin with, do you know what amount of loading your roof is capable of withstanding?  Without this information, knowing how much snow you’ve gotten is meaningless.  Snow load takes into account many different factors including the shape of the roof, the slope of the roof, its wind exposure, the ground snow load value (weight of the snow on the ground), roof obstructions, thermal conditions of the roof and, less obviously, the importance, occupancy, and use of the building. For instance, a hospital could be designed with higher snow load values than, say, a building of self-storage units.
Once you determine the roof snow load value (while there are various calculations and actual calculators floating around the web, if you have the ability to talk to your building engineer, it is probably the best course of action), you need to understand how much snow weighs.  Light, dry, fresh-fallen snow, one-foot deep will weigh approximately 3 lbs/ft2 whereas the same amount of wet, heavy snow could weigh 21 lbs/ft2.  Ice, on the other hand, could greatly outweigh even wet snow.  Ice, at one inch thick weighs approximately 57 lbs/ft2.  With everybody worried about snow loads, perhaps ice loads should actually be top priority!
Remember, these are approximations so, while they aren’t giving you an exact amount, they could give you a ballpark figure to work with to let you know if you are even approaching danger.  Also, keep in mind that while snow will fall fairly uniformly, if you add wind to the equation you could end up with serious snow drifts that can drastically increase loads in certain areas of your roof. 

Once you have these figures, communicate with the people who need to know: those developing your plans, those implementing the plans, and those in charge.  You’ll recall, shortly after a roof collapsed from a heavy snow in Cool Hand Luke, Captain pointed out the reason:

Captain: “What we’ve got here is failure to communicate.”

Designated Safe Removal Areas

If you determine that you need to remove snow or ice from the roof, what are you doing to protect your employees?  In a recent article, Dangers of Accessing a Roof in the Winter, we discussed the inherent dangers of being on the roof after a snowfall, but if your people have to be there to prevent your roof from collapsing, they will need to be protected from falls.  While workers should be protected from falls at all times while on roofs, one of the activities that will put them at the most risk is dumping snow and ice over the side of the building.  During this activity, it is imperative that workers are properly protected.  This can be achieved by tying off to suitable anchor points or by ensuring that workers are safe behind railings (or parapets of sufficient height if you are lucky enough to have them). However, you’re not going to be able to set up those railings safely after you’ve got a ton of snow on your roof.  You need to plan ahead.   Even using a fall arrest system will prove difficult without planning as you may not have a suitable anchor available.

In addition, you’ll need to ensure the area you are dumping is not an area that will have foot traffic below.  If there is any chance of employees or the public passing underneath, you need to cordon off the area until clearing operations have ceased.

Know Your Anchor Points

If you need to get up top to clean the roof, and tying off is your only option, what are you tying off to?  Not only may you not have something that can withstand 5000 lbs. of force per person attached (for the most part), even if you do, it could be buried with snow and difficult (or impossible) to locate.  This will be a big problem on sloped roofs where fall arrest systems, or positioning systems, will be your only option.  In this case, before the snow comes, ensure that you have engineered, raised anchor points installed so you are prepared for the worst case scenario.

Know Who is Working For You

If you don’t have the proper employees for the job, you may need to hire an outside contractor to do the snow/ice removal.  Understand what their capabilities are and their response time before you sign any contract.  In a fast, heavy, wet snowfall, small amounts of time could be critical.  Many people whose main work slows down in the winter will offer snow removal services.  Be cautious.  You need to know if they have the experience, the manpower, and the equipment to properly service your needs.  How and when will they perform removal?  How will they perform it safely?  Are they insured for this type of work?  Don’t open yourself up to lawsuits just because somebody else is trying to make a quick buck in their off-season.  Remember, there are very skilled snow removal people out there, as Liam Neeson, a skilled snow-removal contractor pointed out to a fly-by-night, overpriced contractor in 2008’s Taken:

Mills: “If you are looking for ransom, I can tell you I don’t have money.  But what I do have are a very particular set of skills, skills I have acquired over a very long career.  Skills that make me a nightmare for people like you.”

How Do I Know if There is a Problem?

According to FEMA, there are a number of warning signs.  Should any of the following occur, it could be an indication of the beginnings of roof failure:

  • Sagging ceiling tiles or boards, ceiling boards falling out of the ceiling grid, and/or sagging sprinkler lines and sprinkler heads
  • Sprinkler heads deflecting below suspended ceilings
  • Popping, cracking, and creaking noises
  • Sagging roof members, including metal decking or plywood sheathing
  • Bowing truss bottom chords or web members
  • Doors and/or windows that can no longer be opened or closed
  • Cracked or split wood members
  • Cracks in walls or masonry
  • Severe roof leaks
  • Excessive accumulation of water at non-drainage locations on low slope roofs.

If you observe any of these warning signs, you should have the building evacuated and inspected by a qualified engineer.

Don’t let snow loads sneak up on you.  Take the time to prepare for the worst so that your employees and your property aren’t in any danger.  You can’t put it off until tomorrow, because, as Bill Murray so eloquently pointed out in Groundhog’s Day:

Phil Connors: “Well, what if there is no tomorrow?  There wasn’t one today!”


Dangers of Accessing a Roof in the Winter

Dangers of Accessing

If you live in a part of the country where winters mean snow, ice, and blustery cold winds, you know that outdoor work and work at heights present a unique set of hazards to workers.  Weather conditions cause visibility and traction to go out the window, while numbness can make it hard to feel what you’re doing.  Special precautions must always be taken for winter weather conditions such as these, but when you’re going to work in an inherently dangerous location, such as a rooftop, it’s even more important to make sure you are planning ahead.

Invisible Hazards

You may think the worst thing about snow is having to shovel it or trudge through it, but when you’re on a roof, that beautiful blanket of fresh-fallen snow could be hiding life-threatening hazards that you normally take for granted.  Think about it.  Can you see where you’re walking?  What you are stepping on?  Maybe you feel like you know the roof like the back of your hand, but is it even remotely possible that you forgot about that skylight over there?  Or that low run of conduit near the edge?  Or even just a patch of ice?  Rooftops should be clear before anybody goes to work on them and anybody who is going to work on them, especially to do initial snow removal, should be extremely familiar with the layout.  Even more importantly, protections should be put in place during warmer months to ensure that situations like this are prevented (as much as possible).  For example, skylight rails or cages should be installed, eliminating a potentially fatal hazard, before the snow falls.

Anywhere on your roof has the chance to become an icy obstacle course in winter conditions.  Consider installing an elevated walkway with traction to help provide your employees with safe access to the areas they will need to work.  This could also reduce the amount of snow removal you have to do, by allowing your crews to focus on a set path instead of clearing edge to edge.

In addition, it’s important for you to consider what the conditions could be like at the top of your ladder.  Getting on and off a ladder is always dangerous, but adding ice to the mix could make it even worse, especially if somebody is caught off-guard before they even think to grab the ladder.  The best way to prevent this is to install a rail and gate.  This ensures that the person approaching the ladder has a barrier to prevent them from falling until they are ready to descend.  And, since they’re opening a gate, they’re already holding on to something as they mount the ladder.  Be careful when climbing and descending as well.  Rooftops aren’t the only surfaces that get icy and slippery.  Ensure that you are maintaining three points of contact at all times.


Sure, we have wind year-round, but combined with ice or falling snow, it presents an even greater threat.  A strong gust of wind that catches you while you’re standing on an icy patch can send you flying, especially if you happen to be carrying or get caught behind something that could act as a sail.  Wind combined with falling snow can reduce your visibility to near-zero, causing you to step somewhere you didn’t intend to step.  Tools, materials, and protective equipment could get blown off, causing injury to unsuspecting people below.  Avoid rooftop work as much as possible in high wind conditions.

Obscured Protections

Ideas that seem good in the warmth of spring and the heat of summer can be poor ideas once the snow has fallen.  Do you use painted lines or other low lying markers to indicate safe work areas on your roof?  Do you have safe pathways lined out?  Once your roof is covered in even just an inch or two of snow, these markers are essentially gone.  If you live in a region of the country where snow is an issue, consider eliminating these methods and opt for something raised up that can be seen above a serious snowfall and can withstand some harsh winter winds.

Snow Loads

This certainly isn’t something you should be trying to figure out after a blizzard has passed through and, in fact, your workers will probably never give it a second thought as they are going to assume that the engineers who designed the roof had it all figured out.  Yet, we still see roof collapses on the news every time a major snowstorm hits.  Make sure you know what your roof’s capacity is and what that means in terms of snow.  Don’t forget to add in the weight of workers and equipment that you plan to send up, because this can tip the scales.  If you suspect a snow load might compromise the integrity of your roof, how can you begin the process of snow removal without putting workers in danger?  Obviously, without planning, you’re putting yourself into a very hazardous situation.  Will you call an outside contractor in and turn a blind eye?  Will you send your workers into harm’s way claiming it was an emergency and you were left with no choice?  Remember: don’t let yourself get to the point of emergency in the first place.  Think this through before it becomes urgent.

Winter conditions can be rough, but they are not by any means unexpected.  There is no excuse for not taking them into consideration during your planning and preparation (and there is even less excuse for failure to plan and prepare).  If you have not already done so, gather up all personnel with relevant input and start developing your plan today, not after somebody has come crashing down through a skylight.


Beginner’s Guide: Maximum Arresting Force

Five Ways to Kill Yourself While Using a Fall Protection System

Maximum Arresting Force (or M.A.F.) is a term you will hear frequently used in association with fall protection, so it’s better to understand the term before you encounter it (if you’ve already encountered it, better late than never!).  In simple terms, M.A.F. is exactly what it sounds like: the maximum amount of force produced on your body as your fall is being arrested.  The two situations in which M.A.F. will come up most often are when you are discussing the capability of your personal fall arrest system -- What is the M.A.F. on your body if you fall using our product? When discussing regulatory requirements-- What is the M.A.F. allowed on the body by OSHA or as recommended by ANSI (American National Standards Institute)?

Regulatory Requirements

The regulatory requirements are pretty straightforward:  OSHA requires that M.A.F. be limited to 1800 lbs. of force on the body in a fall when wearing a full-body harness, or 900 lbs. of force when wearing a body belt. However, in 1998, OSHA prohibited the use of body-belts with fall arrest systems. So, the magic number is 1800 lbs. of force. 

How do you meet these regulatory requirements?  By selecting the proper equipment and then using it as directed by the manufacturer.  The manufacturer will design their product and test it in accordance with ANSI Z359.  The tests are to ensure that the product keeps the M.A.F. below the regulatory limits.  Once a piece of equipment hits the market with the ANSI Z359 marking, you can rest assured it will be compliant – IF you use it properly.  For example, the OSHA regulations require that a personal fall arrest system (PFAS) be rigged so that the user’s free fall distance is no greater than 6 feet.  When the manufacturer tests the product, they will do so in a way where the user’s free fall distance is no greater than 6 feet.  As long as you, the actual user, then do the same, the M.A.F. will be less than 1800 lbs. of force.  However, if you connect to an anchor at your feet with a 6 foot lanyard with a deceleration device, your freefall will be 6 feet PLUS the distance between your D-ring and your anchor point.  This added free fall distance could increase the M.A.F. beyond the regulatory limit as well as beyond what your body can safely absorb.

Reducing Forces on the Body

That is what this is all about.  How much force can your body safely absorb?  Are you really “saved” from a fall if the arresting force just caused your ribs to puncture your internal organs or caused your spine to snap?  By using the equipment as intended and staying within regulatory limitations, you are protecting your body and well-being. 

So, how is arresting force limited?  First, as mentioned above, is the freefall distance.  Equipment, rigged properly, will keep your freefall distance below 6 feet (with some exceptions which I will get back to in a moment).  For the most part, your vast majority of lanyards with deceleration devices are 6 feet or less in length.  You can further reduce the force on your body through the selection of an anchor point.  The higher your anchor point, the less free fall you have which results in less force on the body.  Regardless, of where you tie off, though, a fall will cause your lanyard to extend its full length (if it doesn’t, then that means you struck a lower level first and were not wearing the proper fall protection to begin with).  Once a lanyard extends to its full length during a fall, a deceleration device kicks in and you are no longer free falling.  An example of this device is rip-stitching.  This deceleration device is webbing stitched together to act as an energy absorber.  As the force of the fall hits the device, the stitching begins to rip.  Each ripped stitch absorbs energy, thereby directing force away from your body and into the device.  Stitches will continue to rip until you’ve slowed to a stop. 

Other devices used to keep your free fall below 6 feet could be rope grabs or SRLs (Self-Retracting Lanyards).  There are some exceptions, though, so make sure you are reading product descriptions and labels before purchasing.  For instance, a lanyard exists that allows for a 12 foot free fall.  This was created for the purpose of tying-off in a situation where the only available anchor point is at your feet (think of an ironworker on the uppermost steel of a building under construction).  While this free fall distance is greater than 6 feet, the lanyard is designed in a way that still keeps the M.A.F. on the user at less than 1800 lbs. of force.

Staying compliant and keeping yourself safe by ensuring your M.A.F. does not exceed safe limits should not be all that difficult to do.  Make sure you are using trusted brands of fall protection equipment, make sure they contain the ANSI marking, and make sure you are using the equipment as the manufacturer requires.  There is no crazy math, science, or voodoo needed to be done on your part – the manufacturers, OSHA, and ANSI have taken care of all of that for you. 

How Cold Weather Affects Workers at Heights

Five Ways to Kill Yourself While Using a Fall Protection System

Certainly, cold weather poses hazards to anybody working outdoors, but the higher you go, the more intense the conditions can get.  Workers on the ground are facing different hazards than workers on the roof of an office building, who are facing different hazards than construction workers on a skyscraper.  What seems like a normal winter day on the ground could be high winds and extreme temperatures at heights.  Companies and their workforces must understand what they could encounter to properly prepare for them.


If you’re getting your wind information online, the chances are you’re getting ground-level readings.  Depending on the height at which you’re working, those speeds can increase 5, 10, 15 MPH or more.  Planning for a ground-level wind speed when you’re working up in the air could catch workers by surprise, including lift and crane operators.  Scaffolding could be at risk, if not properly built and secured.  In cold weather, scaffold users tend to want to put sheeting up to protect them from the wind, but without holes for the wind to pass through, this could act as a sail and tear the whole scaffold to the ground.  Regular materials such as plywood sheets or tarps could act as sails too, and carry somebody right off a building, roof, or other elevated work area if they are holding on or have the misfortune of being in the material’s path.  Certain parts of your structure could become wind tunnels.  Your best bet, if you have a building or campus where you regularly access roofs or if you’re going to be working on a long term construction project, would be to get your own weather station so you could have accurate readings that mean something to you and your workers.

Ice and Snow

Snow is easy.  Most likely you are aware if it snows, even if some overnight snow caught you off-guard, it’s pretty visible.  Ice, on the other hand, isn’t always so easy to spot.  Pay close attention to your weather conditions as well as any leaks or areas where water tends to accumulate around your site.  Controls being used to protect your workers, such as wetting of concrete while cutting it, could now be posing slip and fall hazards as the runoff freezes.  Since salt doesn’t go so well with freshly poured concrete, make sure you have alternative de-icers so that you are able to give your employees a safe working/walking area.  All of this is dangerous enough on the ground, but when you add heights to the mix you turn a simple (though still potentially harmful) trip and fall into a potential fatality.  Consider the difference between an unexpected patch of ice on a sidewalk, versus an unexpected patch of ice on a roof edge or steel beam.  Make sure you’re cleaning off ladders and scaffolding.  Remember, nobody is allowed onto scaffolding, except the people tasked with cleaning it off, until all snow and ice is cleared.

A Combination of Snow and Wind

If a storm is moving in, visibility could drop to near-zero quickly.  Snow is bad enough, but windy snow – well, you might as well stick your head in a snow bank and call it a day (Note:  I do not recommend this).   Don’t get caught off-guard.  Keep an eye on weather reports so that you can reasonably predict snow events in the winter as you would thunderstorms in warmer weather.  For workers on the ground, it might be easy to evacuate or take shelter, but this might not be the case for somebody who has to descend a scaffold, get off a lift, climb down from a tower crane, or come down from a roof.  A communications tower climber certainly cannot just stop what he or she is doing and get out of harm’s way.  It takes time.  The more advanced notice you have the more chance your workers at heights will be able to make their way to safety.

Cold Illnesses

While in your private life you may be one of those insane people that goes to a Green Bay Packers game at Lambeau Field in January wearing nothing but a pair of shorts and some body paint, but that’s not going to fly at work.  See, it’s all fun and games until someone loses an extremity to frostbite.  Frostbite – and hypothermia – are very real things that you need to be prepared for.  Thankfully, body paint is not usually an acceptable work uniform.  Dress appropriately for the weather, making sure to employ layers.  Not only can you adjust the number of layers as the day goes on, but those gaps between layers help to add additional insulation from wind.  If you’re going to be working on a roof covered in snow, make sure you’re wearing waterproof boots, gloves, or any other appropriate piece of waterproof protection your task requires.    If your clothing gets soaked through, change into something dry as quickly as possible.  Invest in some hand and foot warmers.  The colder you get, the more blood-flow will be directed to your core to protect your important internal organs, leaving your fingers, toes, and other extremities in danger.  Take breaks to warm up when you can and stay hydrated (that means, and this should go without saying on the job, no alcohol – but also, limit your caffeine intake).  When cold illnesses start to take effect, many things can go wrong. You may be numb and unable to properly feel a rung you are reaching for, causing you to slip and fall, or a tool you are holding, causing it to fall on a worker below.  You may feel weaker, you could feel disoriented and you could make bad decisions.  Remember, these cold illnesses can be an issue at any height, but the conditions leading to them are going to be more extreme and get you there faster when you’re working at heights. 

Also, when you begin to suffer these symptoms at heights, the ability to get you the help you need is compromised.  Shelter from the wind, a place to get dry, warm running water, hot liquids to drink, and other things that may be integral to your recovery may not be readily available without completely descending the building or structure you are on – and that takes time.  Valuable time.  And, if your situation is bad enough, there’s a good chance EMTs aren’t going to be able to get to you, so you’re somehow going to have to get down to them.  Do not allow your situation to get this far.

Fall Protection Equipment

Fall protection doesn’t end the moment you take your harness off and toss it on the ground.  Right then and there, you’ve created a problem.  Harnesses and lanyards should be stored in cool, dry places and, in the middle of a cold snap, your worksite will probably be anything BUT cool and dry.  If you allow your equipment to be exposed to the elements, it could get wet, freeze, and thaw.  Lather, rinse, repeat.  This freeze-thaw cycle could cause your fall protection to become brittle or could cause it to rot.  Either way, it certainly will not be saving your life.  Make sure you are storing your equipment somewhere safe when it is not in use.

Rescue Equipment

Your buddy falls off a building, but luckily is saved by his fall protection equipment.  Great!  Now, all you have to do is get the lift over to him to bring him down.  But wait, what do you mean there’s three feet of snow on that side of the building that didn’t get cleared because nobody thought it was necessary?  What do you mean the winds are way too high to safely operate a lift?  Review your fall protection rescue plans and ensure you have options in place if the weather conditions do not allow you to follow your original plan.  If rescue becomes infeasible, you will either need to develop another means or not work in that location until conditions improve to a point that allows for rescue to be possible.  Don’t wait for this to become an issue before you check.  Be proactive.  Proactivity impresses people.  It will make you popular at parties.

Many hazards you face at heights in cold weather are things you could encounter anywhere, but magnified.  Take the time to review your site and adjust where necessary.  Fall protection is tricky even when conditions are optimal, so don’t attempt to do it on the fly.  Stay warm, work safe, and live to go home and enjoy a hot chocolate by the fire with your family (or a beer by the fire alone…whatever, as long as there’s a fire).