Why the roof deserves more thought than the walls

When you are planning a garden cabin, it is easy to spend all your attention on cladding, glazing and flooring, then treat the roof as an afterthought. In practice, the roof is the part of the structure that takes the hardest beating. It faces everything the British weather can throw at it: horizontal rain driven by wind, frost, hail, summer UV, and the constant cycle of wet and dry that slowly breaks down any covering.

The covering you choose affects four things: how long the cabin will last before it needs re-roofing, how much weight the frame has to carry, how much you will pay up front, and how the finished building looks from the bottom of the garden. Get it right and you can forget about the roof for decades. Get it wrong and you will be up a ladder with a tube of sealant every spring.

Mineral felt: the affordable workhorse

Mineral felt — also sold as roofing felt or shed felt — is the covering most people picture when they imagine a garden building. It is a fibreglass or polyester mat saturated with bitumen and finished with a mineral granule surface that protects against UV. It is cheap, light, and easy to handle with basic tools.

• Weight: roughly 2–4 kg per square metre, so almost any frame can carry it.
• Lifespan: budget grades last 5–8 years; heavier premium felt with a polyester base can reach 15 years or more.
• Cost: typically £8–£18 per square metre supplied, and modest labour.
• Minimum pitch: usually 15°, though some products are rated lower with a fully bonded adhesive layer.

Felt's weakness is wind. Lift an edge and the whole sheet can peel back like a sardine tin lid. If you go down this route, fix it properly: nail at close centres, use adhesive on the overlaps, and finish with a nailed timber drip edge so the wind has nothing to grab. It suits small cabins, budget builds and outbuildings where appearance matters less than shelter.

Shingles: timber, bitumen and the aesthetic question

Shingles fall into two broad families. Bitumen shingles are strips of felt-like material cut into overlapping tabs, often with a mineral or slate-look finish. Timber shingles — cedar, larch or treated pine — are individual tapered tiles that weather to a soft silver or stay warm brown depending on the species and finish.

• Weight: around 8–15 kg per square metre, so check your joist spacing and rafters before committing.
• Lifespan: bitumen shingles 15–25 years; quality cedar 25–40 years if ventilated well.
• Cost: £20–£45 per square metre for materials, with timber at the upper end.
• Minimum pitch: generally 15–20°, steeper for timber.

Shingles give the most traditional, garden-friendly look and they handle driving rain and wind uplift far better than felt because each unit overlaps its neighbour. They are also quieter under heavy rain. The trade-offs are weight, cost, and the need for a solid, well-ventilated deck underneath — usually 18 mm exterior-grade ply or OSB covered with a breathable membrane. Timber shingles need periodic inspection, and you should keep leaves and moss out of the gaps so water cannot sit and rot the edges.

Metal roofing: light, long-lived and increasingly popular

Metal covers garden cabins in several forms: corrugated galvanised steel, box-profile sheeting with a factory coating, and standing-seam aluminium or steel panels. All are light for their strength, quick to install in large sheets, and available in a range of colours that can be matched to your cladding.

• Weight: 4–7 kg per square metre for most profiled sheets.
• Lifespan: 30–50 years for coated steel; aluminium will outlast most of us.
• Cost: £25–£60 per square metre depending on profile and coating.
• Minimum pitch: down to 5° with standing seam, 10–15° for corrugated profiles with sealed laps.

Two practical points. First, metal is noisy in rain and hail unless you fit a solid deck and insulation beneath it, which also stops condensation forming on the underside of the sheets. Second, cut edges and fixings must be treated or use coated screws with sealing washers, because bare steel will start to rust. On the plus side, metal sheds snow and leaves readily and needs almost no maintenance beyond checking fixings.

Matching the roof to your cabin and climate

Think about the building, not just the covering. A small 2.5 m × 3 m cabin on a light timber frame is well served by good felt or a light metal sheet. A larger garden room with a shallow pitch, wide spans and insulation will benefit from shingles or standing-seam metal, both of which cope with low angles and wind far better.

Exposure matters too. In coastal or upland areas, uplift and salt are the enemies, so choose a mechanically fixed system with generous overlaps. In sheltered inland gardens, almost anything will perform if it is installed neatly. Also allow for ventilation: a cold roof needs airflow above the insulation to stop condensation dripping onto your ceiling.

Weighing lifespan against budget

The cheapest option is rarely the cheapest over time. Felt at £10 per square metre replaced every seven years costs more across twenty years than metal at £40 that lasts forty. Shingles sit in the middle, with the bonus of looking genuinely handsome on a timber cabin.

A sensible rule of thumb: if the cabin is temporary or a simple store, felt is fine. If it is a garden room you will use daily and want to keep, spend the extra on shingles or metal and fit it properly. Whichever you choose, get the substrate right, fix the edges securely, and the roof will quietly do its job for years while you enjoy the space beneath it.