The short answer
Yes. A sound roof carries an ordinary fall of snow, but heavy wet snow can strain weak timbers, drag gutters off their brackets and leave melt water backing up at valleys and flashings. The harm usually shows after the thaw, as a brown mark on a ceiling or a gutter hanging crooked. Check from the garden or pavement, and ring a roofer if the roof line has dipped.
Snow is rarely the villain on a healthy roof. It finds the weak spots that were already there, and the thaw is when they show.
How snow load strains the structure
A pitched roof is built to shed weather, and a normal fall of snow sits on it without any trouble. Problems start when the load meets a weak point. Wet snow packs far heavier than dry powder, and it can lie for days on a north-facing slope that never catches the sun. Where rafters have rotted at the wall plate, or a purlin, the long horizontal beam that props the rafters part-way up, has sagged over the years, the extra weight shows as a dip in the slope.
Which roofs are most at risk?
Flat roofs and low-pitched extensions hold snow the longest, because it has nowhere to slide. Drifts also build against chimneys, dormers and party walls, which loads one patch far more than the rest. Old garage roofs and outbuildings with thin timbers are the usual casualties. If a ceiling has started to bow, or an upstairs door begins to stick after snowfall, treat it as a structural question and stay out of that room.
Never climb up to clear snow yourself. Ice makes slate and tile slippery, and a ladder on frozen ground can shift under you.
Gutters, brackets and falling ice
Gutters take a beating in snow. A full run of snow and ice is heavy, and the brackets holding the gutter to the fascia, the timber board that caps the rafter ends at the eaves, can pull their screws out of softened wood. Cast iron stays put but can crack when frozen water expands inside it. Plastic runs sag, split at the joints or drop off altogether.
What happens when a gutter is already blocked?
Leaves and moss turn a gutter into a trough that holds water. When that water freezes, it forces the joints apart and leaves an overflow route down the wall. Once the thaw arrives, the water has nowhere to go but over the edge, and it can soak the fascia and the brickwork below. Slates and tiles at the lowest course also get shoved about when a slab of snow slides off the slope above, so look for slipped pieces along the bottom edge.
Stand well back from the building while snow is on the move, and keep the garden path under the eaves clear of people and dogs. A sliding sheet can take a gutter with it, and ice dropping from height hurts.
Melt water at valleys and flashings
Snow does its quietest damage as it melts. Think of a valley, the V-shaped channel at an inside corner where two slopes come together. It funnels a great deal of water into a narrow line. Snow packs into that line and thaws slowly, so the water sits against the joints for far longer than a rain shower would give it. Flashings, the lead or zinc collars sealing the roof where it butts a chimney or wall, face the same test. Any gap in the metal or a crumbling mortar fillet lets the water in.
Why does a leak show up after the snow has gone?
Freezing and thawing work cracks wider each time. Water held back by ice at night runs in as the morning warms, then runs along a rafter and drips off somewhere else, which puts the brown ring on your ceiling a fair distance from the actual gap. Underlay, the membrane beneath the tiles, is meant to catch what gets past, but old or torn underlay cannot do it for long.
Our note on finding the source of a roof leak explains how the trail is followed back to the entry point.
What to check once it thaws
Start inside. Take a torch into the loft and look for damp timber, drips, or a chink of daylight in the covering. Check the ceilings below for brown rings or a bulge. Then walk round the outside and look up: a sagging ridge line, slipped slates or tiles, a gutter hanging at an angle, or lead peeled back from a chimney. Photograph each find with the date, before anything is moved.
Is snow damage covered by home insurance?
It can be, depending on your policy. The Financial Ombudsman Service says a storm usually involves violent wind with rain, hail or snow, and that snowfall by itself can count as a storm. Keep receipts for any temporary protection, and tell your insurer before you commission a permanent repair. Our guide to storm damage versus wear and tear sets out how the line is drawn, and the wider emergency roof repairs page covers the options if water is coming in.
Where water has already got through, stopping it comes before anything permanent. Send a photo of the stain or the hanging gutter to begin, and the survey after that produces one written total for whatever it turns up.
More on snow and roofs
Should I clear snow off my roof?
Usually not, and certainly not from a ladder or by climbing onto the slope. Slipping on ice is a bigger danger than the snow. If you are worried about a bowing ceiling, move out of the room and ask a roofer to assess the roof safely, with proper access set up.
Can snow make a roof leak without any visible damage?
Yes. Melt water can creep under a tile or past a worn flashing without shifting a single slate. The first sign is often a stain in the loft or on a ceiling rather than anything on the slope. Check the loft timbers with a torch once the snow has cleared.
The full picture: Emergency and general roof repairs in Taunton ยท More short answers