Slate in winter
What Does Winter Do to an Old Slate Roof?
Winter trouble on a slate roof starts where water collects: the eaves, valleys and gutters where ice backs up, and old nails that let slates slide. Here's what to watch for, and when it points to replacing the roof.
- Answer first, then the detail
- National Park Service guidance
- Sources checked Oct 30, 2026
Can a slate roof get ice dams?
Yes. Ice dams form on slate the same way they form on any roof: heat from the house melts snow higher up, and the water refreezes at the cold eave. Slate sheds water but isn't watertight, so meltwater pooled behind the ice can run under the slates. Most old slate roofs were laid long before self-adhering ice barriers existed.
The fix for the dam itself is the same on any house: keep warm air out of the attic. On a pre-1940 house that often means sealing around old light fixtures, chimneys and attic hatches before adding insulation, as University of Minnesota Extension recommends (UMN Extension).
Does ice damage a slate roof?
It can. The National Park Service's guide to slate roofs notes that eaves and valleys, where water concentrates and ice dams form, wear out faster than the rest. It also lists ice dams in gutters, valleys and chimney crickets among the causes of broken slates. Those are the places to check after a hard winter.
Look from the ground with binoculars after the snow melts: cracked or missing slates near the eaves, dark gaps in a valley, or pieces of slate on the ground or in the gutter (National Park Service, Preservation Brief 29). One or two broken pieces don't mean the roof is finished; see fix or replace for how to tell.
Do snow guards help on a slate roof?
They stop snow and ice sliding off in one heavy sheet onto people, plants and lower roofs below. The National Park Service notes snow guards were used where ice and snow build up, to avoid dangerous slides. They don't prevent ice dams, and they hold more snow on the roof, so the guards and their fastenings need to be sound.
The Building America Solution Center adds that sliding snow is a danger to people and plantings below, and that snow guards raise the snow load where they hold it (BASC). If your roof has guards, a missing or bent run above a doorway or porch roof is worth noting before winter.
Why do slates slip off in winter?
Usually because the nails have rusted through. The National Park Service calls rusting nineteenth-century cut nails a common cause of slate loss on historic roofs. Winter adds stress: snow and ice can bend the copper tab that holds an earlier replacement slate, letting it slide out. A slate that slips once often means others are close behind.
A few slipped slates on an otherwise sound roof is a job for a slate specialist, and we'll say so if that's what we see. We don't fix individual slates. When slates are slipping across several slopes, it usually means the fasteners are failing roof-wide, which is when replacing the roof starts to make sense.
What should I do if water comes through a slate roof during a winter storm?
Catch the water inside, move belongings and photograph the ceiling and the roof from the ground. Don't go up: slate is slippery in winter and breaks underfoot. Then send us the form. We put emergency tarps on within 24 hours of reading your request, and we read requests Monday to Friday, 9am to 5pm.
A tarp on slate has to be laid with care so it doesn't break more slates, and it can wait until snow and ice make the roof safe to work on. Our storm damage page has the full order of steps.
If I replace slate with asphalt, how is the new roof protected from ice?
A new asphalt roof starts from a sound deck with modern underlayment. Self-adhering ice barrier goes along the eaves and in the valleys, where the old slate roof had none, and new flashing goes at chimneys and walls. Asphalt is also far lighter than slate. The attic still needs to be sealed, or the dams keep forming.
Your local building office confirms how far up the roof the ice barrier has to run. See ice barrier in the glossary and replacing a slate roof with asphalt for what the conversion involves, including historic-district approvals.
Slate in winter questions
Why does my slate roof leak only when it snows?
Can a slate roof be tarped in winter?
Are icicles on a slate roof a bad sign?
Sources and checked date
- National Park Service, Preservation Brief 29: The Repair, Replacement, and Maintenance of Historic Slate Roofs ice damming at eaves and valleys, snow guards, rusted nails, copper tabs
- University of Minnesota Extension, Dealing with and preventing ice dams air sealing and insulation
Last checked 2026-10-30.
Slates slipping or leaking this winter?
Tell us where the house is, how old the roof is and what it is doing. If you have photos, say so and we will ask for them by email. Outside our core area? Send the form and ask.
We answer form requests Monday to Friday, 9am to 5pm. There is no phone line, so the whole conversation stays in writing.