The roof on a shed is easy to ignore until the day a bag of compost goes soggy. Garden buildings are lightly built, often by their owners or by the kit supplier, and their roofs get the least attention of any on a property. Yet the roof decides how long the whole building lasts, because water from above rots the frame, the floor and everything stored inside. The choice of covering depends on the building's pitch, its frame, what is kept in it and how much you want to spend. This guide runs through the common choices for sheds, workshops, summerhouses and garden rooms and explains how long each tends to last, and why.
What kind of building is it?
Outbuildings fall into rough categories, and the right roof differs between them. A basic shed for tools and bikes needs a covering that keeps rain out and costs little. A workshop where you spend time, perhaps heated, needs insulation and a roof that does not drum in a downpour. A summerhouse or garden office is lived in, so condensation, comfort and appearance matter. A log cabin has thick roof boards and a heavier structure, and a pergola or open store may not need a waterproof roof at all. Matching the roof to the use saves money in one direction and avoids rot in the other.
The frame and deck also vary. Many sheds have thin, tongue-and-groove or OSB roof boards on light rafters. Cabins have thicker boards. Workshops built from block or brick can carry nearly anything. Check what you have before choosing, since a heavy covering on a flimsy frame sags.
Mineral felt
Roll mineral felt is the traditional shed covering and still the commonest. A roll of bitumen-coated felt with a mineral surface is nailed to the boards in overlapping strips, with clout nails and a bonding adhesive at the laps. It is cheap, easy to fit and straightforward to repair. Its weaknesses are its short life and its vulnerability at edges and laps, where wind lifts it and rain gets in. Basic shed felt, which is thinner and cheaper, ages more quickly than a heavy-duty or reinforced product. Sunlight cracks the surface, frost opens the joints and moss collects on shaded roofs. Our answer on how long shed felt lasts explains the factors in detail.
Felt shingles
Felt shingles are small bitumen tiles that give a neater, more traditional look to a pitched shed, summerhouse or cabin. They need a firm boarded deck and a minimum roof slope, and their life is longer than basic roll felt but still a light-duty one. They shed water through overlap rather than through a continuous skin, so they are not a choice for a flat roof. Our guide to felt roof shingles covers fitting and limits.
Heavy-duty felt systems and torch-on
A step up from roll felt is a built-up system of reinforced, multi-layer bitumen felt, applied by adhesive or flame. It is more durable, suits flat or low-pitch workshops and garden rooms, and gives a better result around rooflights and edges. The fire risk with torch-on is real near timber, so cold-applied or self-adhesive versions are often used on garden buildings. Our guide to torch-on felt roofing explains the system.
EPDM rubber and GRP
For a flat or near-flat garden room or workshop, EPDM is a popular choice. A single sheet is bonded to the boards and dressed over the edges, with no joints in the middle and a long life when laid on a clean, dry, smooth deck. GRP is the other option, a rigid laminate finished with a coloured topcoat, and it suits awkward shapes and roofs that will see foot traffic. Both cost more than felt and typically last longer. Typical UK cost guides for a fitted EPDM roof run from £70 to £120 per m², depending on the source. Your fixed quote follows the survey. Both materials depend on a dry deck: a damp board under rubber or resin will eventually cause bubbles or rot.
Profiled sheets
Corrugated and box-profile sheets of coated steel, plastic, fibre-free cement or bitumen are common on stores, workshops and lean-tos. They are light, quick to fit and suit a low-pitch roof if the maker's minimum pitch is met. The drawbacks are noise in rain, condensation underneath and the need for sealed fixings and correct overlaps. Corrugated bitumen sheets are cheap and quiet but can sag in heat and fade. Our answer on whether corrugated bitumen sheets are any good weighs them up, and the guide on which roofing sheet is best compares the main types.
Tiles, slate and shakes
A substantial pitched outbuilding with a proper frame can take clay or concrete tiles, slate or man-made slate. These are the longest-lived and most attractive options, and also the heaviest and dearest. They need a strong roof structure, battens and underlay, and ridge and verge components fixed mechanically in line with BS 5534. For a summerhouse that is also a feature of the garden, a tiled roof can be worth the outlay. For a basic shed it is out of proportion.
Green and sedum roofs
Living roofs appeal on garden buildings, where they soften the look and help with water. They are heavy when wet, so the frame must be designed for them, and they need a waterproof membrane under the planting plus an edge to hold the substrate. They are a specialist choice rather than a default, and our short answer on a sedum roof on a flat roof covers the main points.
| Covering | Suits | What usually limits its life |
|---|---|---|
| Basic roll felt | Plain sheds, low budget | Thin material, lifting at laps and edges |
| Heavy-duty or built-up felt | Workshops, flat or low-pitch roofs | Hardening in sun, poor edge detail |
| Felt shingles | Pitched sheds, summerhouses, cabins | Curling tabs, wind, moss |
| EPDM or GRP | Garden rooms, flat roofs | Punctures, a damp or flexing deck |
| Profiled sheets | Stores, workshops, lean-tos | Corrosion, fixings, condensation |
| Tiles or slate | Substantial pitched buildings | Frame movement, slipped tiles |
What decides the lifespan
Manufacturers give life figures under ideal conditions, and an outbuilding rarely meets them. In practice, five things matter most. The first is the deck: boards that stay dry last, and boards that stay wet rot. The second is the pitch and drainage, since a roof that holds water ages faster. The third is the edge detail, where felt lifts and water enters. The fourth is the setting: shade, overhanging trees and a damp garden promote moss and decay. The fifth is maintenance. Clearing leaves, cleaning gutters, re-fixing a lifted corner and checking after storms extend any roof, and neglect shortens every one. This is why two sheds with the same felt can age very differently.
Boards, bearers and the base
A roof is only as sound as the boards under it, and on a garden building the boards are often the weak link. Roof boards of thin plywood or OSB swell and delaminate when wet, and shiplap or tongue-and-groove boards shrink and open gaps. Before a new covering goes on, we check each board for softness, replace any that are damaged and make sure the surface is flat, as a ridge or a gap shows through a thin membrane. Rafters and bearers that hold the boards should be checked for rot at their ends, where they sit on the walls.
The base of the building matters too. A shed standing on soil or slabs that hold water will draw damp into the walls and floor, no matter how good the roof. Raising the building on bearers or a base of concrete or paving keeps the timber dry. A small overhang at the eaves sheds water clear of the walls, and a water butt or gutter stops splashes. These are small additions that extend the life of the whole building.
Repairs between replacements
Most outbuilding roofs can be kept going with simple maintenance. Clear leaves and moss from the surface, using a soft brush. Re-stick lifted felt laps with bitumen adhesive, and nail down loose edges. Patch splits with a section of felt that extends well beyond the damage. Re-seal the joints at a flue or vent, and replace any sheet that has cracked. Check after storms and again at the end of the autumn leaf fall. These tasks take little time, and each one removes a way in for water. The point at which repair stops being worthwhile is when the boards are soft, when patches have multiplied or when the covering is worn across its whole surface.
Insulation and condensation in garden rooms
A heated garden room is vulnerable to condensation, because warm moist air meets the cold underside of a roof. Rot starts out of sight. Insulation above the deck, with a vapour layer beneath, keeps the structure warm and avoids a damp void. A cold roof needs ventilation at the eaves. Our comparison of warm roof and cold roof construction explains the principle, which applies on a small scale to garden buildings as much as to extensions.
Wind, snow and the exposed garden
Garden buildings sit in open ground, where the wind catches them. A light roof can lift if its edges are not fixed down, particularly after a storm, so the felt, sheets or tiles should be fixed at the eaves, verges and ridge to the maker's schedule. Snow adds weight, and a flat roof with a spongy deck or a light frame can sag under it, so brushing it off from the ground with a soft broom helps. Heavy drifts against one side of a building, or water pouring off a neighbouring roof onto the shed, are also worth correcting at source with a gutter or a redirected downpipe.
Planning, nesting birds and neighbours
Re-covering an outbuilding roof normally raises no planning issue, though changing its height or shape can, and outbuildings near boundaries are subject to rules, so ask your council's planning team if you are altering it. Sheds and garden rooms are favoured by nesting birds and sometimes bats under the eaves, and both are protected, so if you find them, the work may need to wait or be surveyed first.
Getting a roof assessed
If a shed or garden room is leaking, we can survey it. We photograph the roof and boards, say plainly whether a repair or a re-cover is sensible, and give a fixed written quote. We cover Basingstoke and the towns around it, and workmanship carries a written ten-year guarantee. Our wider garage and outbuilding work is described under garage roofing, and 01256 213956 is the number to ring when you are ready. If you are weighing a straight replacement against a cheaper patch, tell us which and why, and we will price it fairly with the evidence in front of you.
