Autumn is a strange season for anyone with a cabin at the bottom of the garden. The light is lovely, the cabin looks at its most inviting, and yet the weather is quietly getting ready to test every fixing, joint and seal you own. By the time the first named storm is forecast, it is usually too windy and too wet to do anything sensible about it. The trick is to use a calm, dry afternoon in September or early October to walk round the building with a screwdriver, a torch and a notepad — and to fix the small things before they become expensive ones.

Start with the fixings and the roof

Work from the ground up or the top down, but be systematic. A cabin flexes slightly through the seasons, and screws work loose in a way that is easy to miss from standing height. Take a ladder out on a still day, keep both feet on the rungs, and never lean out over the edge of a roof when you can inspect it from the ground with binoculars instead.

• Check roof sheets, felt, shingles or membrane for lifted edges, splits and missing fixings. On metal roofs, look at the sealing washers under each screw and give any that have backed out a gentle quarter turn — no more, or you will crush the seal.
• Look at ridge cappings, flashings and the join where the roof meets a wall. These are the first places driving rain finds.
• Run a hand along the cladding and tap the boards. Hollow or springy patches suggest a fixing has gone.
• Check window and door hinges, handles and locks. A door that has started to catch is often telling you the frame has moved or the base has shifted.
• If the cabin is bolted to a concrete pad, a timber base or post bases, check the anchor bolts and the condition of the bearers underneath.

Keep water moving away from the timber

Water does far more long-term damage to a garden building than wind ever will. Most of it arrives quietly, as rainwater sitting where it shouldn't. Clear gutters and downpipes of leaves and moss now, then again after the last of the leaves have fallen. A blocked downpipe sends water straight down the cladding and into the base.

• Pour a bucket of water into each gutter run and watch where it goes. If it pools, find the obstruction rather than hoping it clears.
• Check gullies, drains and soakaways are free of debris and not hidden under a paving slab or a pile of pots.
• Make sure the ground falls away from the cabin on all sides — a fall of about 150mm over the first metre is ideal. A shallow gravel trench along the uphill side will catch water before it reaches the timber.
• Check that the cabin sits on bearers at least 25mm clear of the ground, with no soil or bark chippings bridged up against the base.
• If you have a water butt, check the overflow and the tap. A leaking tap over winter slowly saturates the ground beside the wall.

Secure anything the wind can lift

Garden furniture becomes a projectile in a gust of 60mph, and a flying parasol can do more damage to a window than a falling branch. Anything light, flat or sail-like is a candidate for either storage or strapping down.

• Stack and cover furniture, or bring it inside the cabin if there is room. Store parasols horizontally with the fabric wrapped tightly round the pole.
• Anchor trampolines properly with ground stakes, or dismantle them. Turn them upside down and weigh them down as a last resort.
• Chain or lock gas bottles, wheelie bins, log store covers, compost bins and water butts to something solid.
• Take down hanging baskets, bird feeders, wind chimes and bunting.
• Check shed and cabin doors latch firmly. A door that rattles all night will eventually tear its hinges out of soft timber.

Deal with overhanging branches

Trees are the biggest single cause of storm damage to garden buildings, and it is almost always dead wood, weak unions or branches that have grown across the roof since last winter. Take a slow walk round the cabin and look up.

Aim for at least two to three metres of clear air between the roof and any branch, and remove anything visibly dead, crossing or rubbing. Be careful about timing: many trees — cherries, plums, acers and birches in particular — are best pruned in late summer, and wound fungi spread more easily in wet weather. If a branch overhangs a neighbour's garden or a public footpath, check who owns the tree before you cut, as you may need permission. For anything above head height, or any tree that looks unstable at the base, bring in a qualified tree surgeon. It costs far less than a new roof.

Check seals, vents and signs of damp

Driving rain gets in through the details, not the panels. Walk round with a tube of external-grade sealant and a critical eye. Renew mastic around window and door frames, and check that a drip bar or sill sits above the threshold so water runs off rather than in. Make sure any vents are clear of cobwebs and debris, and that rain cannot blow straight into them — a simple deflector can make a surprising difference.

Inside, look for fresh tide marks, soft patches on the floor near the walls, and that faint musty smell that says damp air is trapped. A small dehumidifier or a couple of ventilation gaps will keep a well-sealed cabin usable all winter, and it is much easier to fix a damp problem now than in February.

When the warning comes

Once a storm is named, stop working at height and simply run through the quick wins. Put away anything loose, latch every window and door, and turn off and unplug the power to the cabin if it is fed from an outbuilding supply. Move cars away from large trees, and bring in anything from the log store that you will not need for a day or two. Afterwards, inspect from the ground before you switch anything back on, and look for water ingress before it has time to soak into the timber. A couple of hours now, on a mild afternoon, is usually the difference between a cabin that shrugs off the winter and one that needs a new roof in January.