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Community and Q&A

Post-blow snow woe (snow loading and depth after deep energy retrofit)

Mark Baker | Posted in Energy Efficiency and Durability on

This post asks two questions about snow after insulating , (A) changes in loading and (B) changes in the snow line and how to flash for it.


When it snows, our current (massive) heat loss melts most of it off the roof… and of course we get ice dams. After proper sealing/insulating,. we’ll store all the snow all winter, and in my area you never know when it will rain after snow. The 1920 house has a simple 20×30 hip roof framed with unsupported 2x6s. Should I be worried about possibly overloading the roof when we stop “removing” the snow via melting? I have a St.Eng. doing some other work for me, so I’ll ask him also, but I am very interested in others’ stories/views.


The attached front porch has a gable roof, and the attached back porch has a shed roof. Each roof is within a few inches of a window. Right now, the snow never really piles up all the way to the glass and melts away fairly quickly. After we insulate, this will change. Ideally the building design would have put the window above the snow line of a well-insulated structure, but since I’m retrofitting, how do you flash those windows so your wall insulation stays dry? Please share any links that might help!

Thanks, GBA and readers are awesome!

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  1. Charlie Sullivan | | #1

    We had a similar roof, and a structural engineer spec'ed some additional bracing that was easy and inexpensive to add.

    Ideally good window flashing designed for rain would work for snow too but if you have doubts about it, opening the window and shoveling a little right around the window might be called for after a big snowfall.

  2. GBA Editor
    Martin Holladay | | #2

    To make sure that your roof structure can handle expected snow loads, consult an engineer.

    When snow gets deep, it's possible for windows to get buried. As Charlie points out, those of us who live in climates with lots of snow become friendly with our snow shovel.

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