What should I do if snow builds up on a roof or conservatory?

Most UK roofs carry snow easily, and the real risks are conservatories, flat roofs, carports and ice dams at the eaves. Almost nothing about it is a job you should be doing from a ladder.

Difficulty: beginner
Time: 30 min
Read: 6 min
Safety: warning

Short answer

Leave a pitched tiled roof alone — it is designed for it. Watch a conservatory, a flat roof, a lean-to or a carport, and clear snow from ground level with a soft brush on a pole if it is building up deeply. Get people out from underneath anything that is creaking or sagging. Ice at the gutter line is a heat-loss problem to fix in the loft, not something to chip at.

A well-built pitched roof in the UK handles the snow loads we get, and the snow slides or melts off. Problems concentrate where the structure is lighter or the pitch is shallower: conservatory roofs, glazed lean-tos, carports, flat extensions and older polycarbonate. Wet snow is roughly three times heavier than fresh dry snow, so the dangerous moment is often a thaw with rain, when the existing snow soaks up water and the load doubles overnight.

Safety

Never go onto a snow-covered roof, and never lean a ladder against a gutter loaded with snow or ice. Falls from roofs and ladders in winter are among the most serious domestic injuries there are. If snow load is genuinely threatening a structure, get everyone out from under it and ring a roofer or, if collapse looks imminent, 999. Never chip at ice on a roof edge — it damages the covering and drops heavy ice onto whoever is below.

What you'll need

A soft brush or roof rake on a long pole (optional)
Warm gloves and boots with grip
Binoculars, for checking a roof from the ground (optional)
A torch for the loft (optional)

How an ice dam forms at a roof edge

Step by step

Leave a normal pitched tiled or slated roof alone.It is designed for the snow load and for the water. Walking on it, raking it or trying to clear it does far more damage than the snow does, and it is where people fall.
Watch the lightweight structures instead.Conservatories, glass and polycarbonate lean-tos, carports, porches, flat roof extensions and greenhouses. These are the ones with a real load limit, and deep or wet snow is what finds it.
Clear a conservatory roof from the ground, with a soft tool.A soft brush or a purpose-made roof rake on a telescopic pole, worked from the ground, pulling snow down towards you a little at a time. Never a shovel, never a metal edge, and never from a ladder or from on top.
Get out from underneath anything creaking, cracking or sagging.Noise and visible deflection mean the structure is at its limit. Close the door on it, keep everyone out, and get a roofer or structural engineer to look. If it is about to come down, ring 999.
Watch for the thaw-and-rain combination.Rain falling onto lying snow is the highest load a UK roof usually sees, because the snow acts as a sponge. That is the point at which to clear a conservatory or flat roof, ideally before the rain arrives.
Keep gutters and downpipes clear before winter, not during.A blocked gutter fills with ice, and the ice is what tears gutters off and dams meltwater back under the tiles. Clearing them in autumn is the whole prevention.
Treat ice at the eaves as an insulation problem.A ridge of ice along the gutter line means heat is escaping into the loft, melting snow higher up, and the meltwater is refreezing at the cold overhang. The cure is loft insulation and loft ventilation, not attacking the ice.
Check the loft during and after a heavy snowfall.Look for damp on the underside of the roof, wet insulation, and fine snow that has blown in through vents. Drifted snow inside a loft melts into the ceiling below and looks exactly like a roof leak.
Clear the path and the doorway before you clear anything else.Snow sliding off a roof or a conservatory can come down in one slab and is heavy enough to hurt someone. Keep the area under the eaves clear of people, cars, pets and bins.
Photograph any damage before you clear it.Snow load damage is covered by the storm section of most policies, but insurers exclude gradual deterioration and poor maintenance. Photographs taken before clearing are the evidence.

Tips

Fresh dry snow weighs roughly 100kg per cubic metre; wet or compacted snow can be three times that. A 300mm covering of wet snow on a small conservatory roof is well over a tonne.
Never use salt, de-icer or hot water on a roof or a conservatory. Salt corrodes fixings, aluminium and lead, and hot water refreezes lower down and makes the dam worse.
Snow guards along the eaves of a steep roof above a doorway or a path stop slab avalanches, and are a sensible fixture on a roof over an entrance.
Icicles along a gutter are a symptom worth reading: they mean heat loss into the loft. They also fall, so keep the ground under them clear.
If you have solar panels, snow usually slides off them faster than off the surrounding roof, in one sheet. Do not stand under them and never brush them clear from a ladder.

Common mistakes

Going up a ladder to clear snow — Ladder feet slip on ice, the gutter is loaded and may give way, and a roof under snow hides everything underfoot. Almost every serious injury in this category starts with a ladder.
Chipping ice off a roof edge or gutter — It cracks tiles, tears felt and lead, and drops heavy ice below. The ice is a symptom of heat loss and the fix is in the loft.
Using a shovel or a hard scraper on a conservatory roof — Polycarbonate scratches and cracks, and sealed units and glazing bars are easily damaged. A soft brush on a pole from the ground is the only sensible tool.
Assuming a leak in a thaw is a roof fault — Blocked gutters, ice dams and drifted snow in a loft all produce water inside during a thaw and then stop. Establish which it is before commissioning a roof repair.

If it doesn't work

Water coming through a ceiling during a thaw

Cause: Ice dam at the eaves backing water under the tiles, or snow blown into the loft — Fix: Contain it with buckets and pierce a bulging ceiling to release the water in a controlled spot. Once it has thawed, deal with the cause: loft insulation, loft ventilation and clear gutters.

Gutter pulled away from the fascia after a freeze

Cause: Weight of ice, usually in a gutter that was already blocked — Fix: Leave it until the ice has gone, then refit or replace with brackets at closer centres. Clear the gutters every autumn to prevent it recurring.

Conservatory roof creaking under snow

Cause: Load approaching the structure's limit — Fix: Clear the room, close the door, and clear the roof from the ground with a soft tool. If it is still creaking after clearing, get it inspected before using the room again.

Boiler shut down during a cold snap

Cause: Frozen condensate pipe, not the snow — Fix: Thaw the external condensate pipe with a warm — not boiling — water bottle or a cloth soaked in warm water, then reset the boiler. Lag or upsize the pipe to prevent it recurring.

Questions people ask

How much snow is too much for a conservatory?

There is no single figure — it depends on the structure, the pitch and whether the snow is wet or dry. As a practical rule, start clearing a conservatory or flat roof from the ground once the snow is more than about 200mm deep, and clear it sooner if rain is forecast on top of it.

Should I clear snow off a flat roof?

Only from the ground or from a safe permanent access, and only if it is deep or wet. Flat roofs shed nothing, so the load stays until it melts, and a blocked outlet turns melt into standing water. Keeping the outlets clear before winter matters more than clearing snow after.

Am I liable if snow slides off my roof onto someone?

Potentially, if you knew it was a hazard and did nothing. Keeping the area under the eaves clear and fitting snow guards above a doorway or a public footpath is the sensible response.