A Snowy Deck: The Dos and Don’ts For Clearing Your Deck of Snow

In the poem “Stopping By Woods on a Snowy Evening” the beloved American poet, Robert Frost, describes a tranquil New England scene, as he “watch[es] his woods fill up with snow…” and praises “the easy wind and downy flake”.  Come shovel my driveway, Mr. Frost.  There are no “downy flakes” here.  Just mounds of heavy, wet, icy snow to strain my back.  And worse, that snow also covers my backyard deck.  When I finish clearing my driveway in 2 hours, must I then shovel off my deck?  Actually: You don’t. 

 

Here’s a list of Dos and Don’ts when it comes to snow and your deck:

 

1) Don’t shovel your deck to avoid collapse.  Building Codes require decks support more snow than most roofs.  A properly built deck is not likely to collapse from the weight of snow.  Here’s a rule of thumb: Your deck rails are probably 36” high.  Don’t worry until the snow is above your rails (deeper than 3 feet.)  If you can see the rail tops, you’re OK — even with a little rain.  When snow is deeper than 3 feet, begin to worry.  When snow is deeper than 3-1/2 feet, begin to shovel.

 

2) Don’t shovel your deck to protect the wood. Water and snow are not nearly as harsh on wooden decks as many would have you believe.  In fact, in the south many experts recommend cooling wood decks on very hot days with water.

 

3) Do clear the snow to provide an exit path from your house.  You should always have two separate exit paths from your house for safety.  Indeed, Building Codes require two.  If clearing that second exit path dictates you shovel some of your deck, then do it.  But all you need clear is a path 3ft wide;  no need to shovel the entire deck.  Pay particular attention to your stairs and the hand rails — the “banisters” or “grab rails” — you’ll need to grab those quickly if you slip.

 

4) Do clear the snow to provide a path to your grill if you cook outside during the winter, or a path to the bird feeder, to feed your winged friends.

 

5)  Do shovel the snow if you want the exercise.  I guess you could call it exercise — if you are young.  But by middle age, I’d call it work.

 

6) Do shovel your deck when the accumulated snow exceeds 3 ½ ft and you suspect the deck’s structure may be sub-par.   Until recently, that much snow had been reserved for Canadians, but suddenly Americans can enjoy it as well. 

 

7) Do not dump snow from a roof onto your deck.  Several feet of heavy, compact roof snow, thrown on top of an already snow-covered deck can severely damage it – whether you throw it onto the deck or Mother throws it on.

Remember what your high school physics teacher said about the force of falling objects? Force = Mass x Acceleration.  Well, “Mass” here is the snow from your roof and “Acceleration” is the speed it gains falling toward your deck.  The resulting “Force” can be massive, especially for compacted snow:  The greater the height of the fall, the greater the resulting force on your deck.

A worse threat is falling ice.  Its impact may be localized, but it is heavier and does not compress when it hits your deck.  Instead, your deck compresses…and breaks.  Here is a damaged rail and what remains of the culprit:

 

Ice damage from roof. If snow can damage your deck, is ice even worse?

 

Yes, winter can damage your deck.

 

3 ½ feet of snow weighs somewhere between 42 and 63 pounds per square foot.  That’s right at the Building Code’s design load for decks — 40 or 60 psf, depending on your location.  Construction standards include a safety factor of 2.5 to 1.  That means a deck perfectly built to 40 psf will not fail until 100 psf.  So is your deck safe under 6 or 7 feet of snow?   No.  With snow between 3 ½ feet and 8 feet, your deck — and you — survive in the limbo of that safety margin.  Any imperfections in that deck — knots, splits in the wood, sloppy carpentry, weak nails instead of screws, wood that has dried and shrunk — reduce the deck’s safety.  Indeed, weight above that 40 or 60 psf design load brings you not into a safety zone, but into a danger zone.

 

Ok then, you’ve decided to clear that thick white menace from your deck.  How best to avoid damaging your deck? Here are some TIPS:

 

1. Before it snows, make sure there are no nails or screws protruding from the flooring; these can catch a shovel or a foot.
2. The best way to clear a little snow is with a broom. A simple corn broom is best. It works well if the snow is fairly light and only a few inches deep.  Light, fluffy snow is ideal, for you can sweep it under the rails;  and, more importantly, the broom will not scrape, scratch or gouge your deck.  And a corn broom will not catch on any protruding nails or screws.
3. Or, if you have only a couple of inches of truly light snow, you can clear a path with a leaf blower. Really — it’s almost fun.
4. When the snow is deep – say, over four inches – you’ll need a shovel. Use a plastic shovel with a plastic or rubber blade. A metal blade can easily scratch or gouge your deck.  Be especially gentle if your deck flooring is cedar or redwood;  they are soft woods and most vulnerable to damage.  Pressure treated pine is OK;  hard woods like mahogany and especially ipe will fare better, but all wood is vulnerable. 
5. Shovel parallel to the deck boards, not across (perpendicular to) the deck boards. Otherwise the front edge of your shovel will likely catch the edge of a deck board and cause damage.
6. Never chop ice on your deck, even with a plastic shovel. You’re guaranteed to also chop your deck. Instead, melt the ice with chemicals.  Use chemical power rather than muscle power.  There are numerous choices for wood and synthetic decks.  Rock salt or halite works by lowering the freezing temperature of water down to 15 degrees.  Calcium chloride* is more effective;  it interacts with ice and snow to create heat that melts ice down to 25 degrees below zero.  Happy Paws ™ snow melter claims to be safer than calcium chloride for pets and the environment.

 

So if you need to or want to, sweep, blow, or shovel that snow.  Just be careful not to scratch or damage your deck, and be especially careful walking on your deck afterward.  Ice has a way of creeping back for revenge.

 

NOTES: * Calcium Chloride is sold under many brand names, including “Safe Step”, “Winter Heat”, “Safe-T-Power”, “Quick Joe” and is available during the winter at hardware stores, lumber yards, and even super markets.