Maintaining your roof during snowfall season

How much snow is too much snow on your roof?

With the recent dump of snow in the South Island and inner North Island, we felt it would be a good idea to address the things homeowners should be aware of in snowfall areas.

When you live in snowfall areas there are two things that you should be aware of in terms of roof maintenance during snowfall; the snowfall capacity of your roof, and the formation of ice dams.

The first thing to ask yourself when determining if there’s a requirement to remove snow from your roof is: “What is my roof pitch?” A flat roof is often more susceptible to collapse than a sloped roof, simply because a sloped roof disperses weight whereas a flat roof cannot. Generally, the steeper your roof angle the more snow it can hold, and in most cases, it won’t collect as much snow in the first place as it tends to slide off.

The good news is that your roof is required by building codes to withstand heaviest snows for your part of the country. A good way of telling if there’s too much snow on your roof is if your interior doors begin to stick, as that can be a good signal that there’s enough weight on the centre structure of the house to distort the door frame.

The second consideration in snowfall areas are ice dams - although this is not very common in New Zealand, it is still worth considering it, and its potential impacts. What is an ice dam? An ice dam is a ridge of ice that typically forms along the edge of a roof at spouting’s and even in internal gutters and prevents melting snow from draining away. Ice dams can also form around skylights, vents, and anywhere two inclined sides of the roof meet (i.e. valleys).

There are two ways of preventing ice dam formation:

  1. Invest in insulation and ventilation

    Poor insulation and lack of adequate ventilation in the attic space causes the roof deck to heat up and melt the snow above. When it does, the water flows down the roof and gets backed-up behind the dam with nowhere to drain off. Not only does this pool of water eventually refreeze into more ice (and continue to grow), but in the meantime, the water can work its way under the roof. So, the key is to improve the insulation in your ceiling cavity, to minimise the heat that enters the ceiling, to absorb the rest as much as possible, and to improve the ventilation in your ceiling, so the heat can escape. It is important to look for places where heat is being sent directly to your ceiling, and either block or remove them.

  2. Get the snow off your roof

    If you decide that the snow must be removed – don’t do it yourself! Climbing on a roof especially in snowy conditions is not recommended. Instead, contact a roofing professional for assistance.
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