From Harford County government:
A warning for business owners about the record snowfall in Harford County:
As snow begins to melt and pack, Harford County Emergency Services and the Department of Inspections, Licenses & Permits urge area businesses with flat roofs to be wary of snow accumulations and snow drifts on roofs caused by the recent historic blizzard. Snow will become heavier and more dense as it melts, refreezes and melts again.
Business owners should ensure that snow is removed in accordance with FEMA guidelines for working on a roof.
In addition, please check roof drainage systems and make sure they are functional to prevent ponding in case of rain. We recommend that snow removal be performed by a professional.
Contact information for businesses to report damages from the winter storm:
Also, as we transition into recovery we ask that you inform your local emergency management agency with information if you have had any damage to your business as a result of the winter weather.
The contact number for Harford County Emergency Services to report such damage is 410-638-4900. In addition, if you have any questions regarding insurance, you can contact the Maryland Insurance Administration at 800-492-6116 (press 0 for receptionist).
Does snow really become heavier as it melts, compacts, refreezes, etc? I understand it becomes denser per square foot (so a shovelful of compacted snow weighs more than a shovelful of powdery snow), but if a square foot of fluffy new snow weighs XX lbs on a roof, and it compacts to a lower height, doesn’t it still weigh the same, or is it absorbing moisture and actually increasing in weight? Thanks!
The mass is more or less the same. The problem is that, being more dense, wet snow puts more stress on a roof than the same volume of dry snow. As dry snow melts down, it does become denser; therefore, the a volume of wet snow is heavier than the same volume of dry snow (which is why I have to take smaller bites of the stuff that blocks my access to the road [thanks, plows] than I did when it was drier). However, as the snow melts, its volume decreases; additionally, some of the mass is carried off either by liquid runoff or by evaporation. I wouldn’t say it’s absorbing moisture and increasing in weight. It’s just that by volume, dense, wet snow is in fact heavier than dry, powdery snow; but melting decreases the volume.
Thank you! That makes sense and is what I thought was the case. Since the storm, I’ve read several articles that warn property owners to check their roofs because snow becomes heavier as it melts,causing roofs to collapse. I read these articles while looking out at my own roof with a drift of snow 4 feet deep, wondering if the snow was getting heavier and about to cause a collapse. I finally decided that, absent any additional precipitation, the snow that was there weighed the same as it did when it fell, minus any moisture lost to evaporation or melting/runoff.
I know this is probably way, way too much thought to put into all this, but in between shoveling I had a lot of time on my hands while I was snowed in!
In considerations of the moisture and wetness caused by the climate,
these two are the two components of the house that are always directly affected.
This enhances the product to give more life to the sheet.
* When the base sheeting is coated with the aluminium and zinc
alloy only, that is no further coloured coatings, it does look similar to the
old galvanised iron, but it does not have the spangled effect.