Storing a classic car: the complete guide

Knowing why a stored car deteriorates makes it easier to decide which precautions matter for yours.

Damp and corrosion

Steel rusts when there is water on its surface, and the amount of water on a metal surface rises with the humidity of the air around it. The Canadian Conservation Institute, which advises museums on caring for collections, says that above about 65% relative humidity all metal corrosion speeds up significantly, and that at moderate humidity (40 to 55%) most metals show no immediate problems. Salt makes matters much worse: salt-contaminated iron can corrode at a relative humidity as low as 20%. A car put away with road salt still on it is therefore at risk even in a fairly dry garage.

Damp also harms the interior. Mould becomes possible on some surfaces at around 60% relative humidity and grows quickly in wetter air, attacking leather, carpets, headlinings and fabric hoods.

Condensation

When warm, moist air meets a surface colder than its dew point, water condenses on it. A car in an unheated garage cools down overnight and in cold spells, and its metal can stay colder than the air for some time when the weather turns milder. The result is a film of water on and under the car, often in places you cannot see. This is why garages seem to "sweat" in a thaw.

Batteries

A lead-acid battery slowly loses charge while it stands, and a battery left to discharge deeply can be damaged beyond recovery. Battery makers advise keeping a stored battery charged and checking it regularly.

Tyres

Tyres that carry the car's weight in one place for months can develop flat spots, and rubber ages and cracks whether or not the car is used.

Brakes and moving parts

Brakes left applied can stick to the drums or discs. Fluids that are not circulated, seals that dry out and cables that are not moved can all give trouble when the car is first used again.

Fuel

Petrol ages. The RAC puts its shelf life in a sealed container at around six months at 20°C. Ethanol blends add their own problems: the Federation of British Historic Vehicle Clubs (FBHVC) warns that storing petrol containing ethanol over a winter can lead to corrosion in fuel systems, and that leaving a fuel system to dry out can make rubber seals and gaskets shrink and crack.

Rodents

A quiet garage is an ideal winter home for mice and rats, and a stored car offers shelter, nesting material and wiring to gnaw. Insurance claims for rodent damage to cars are rising: Aviva reported a 28% increase in such claims in 2024, with an average claim of £2,494.

A garage

A dry garage is the best ordinary home for a classic, but not every garage is dry. Footman James, a classic vehicle insurance specialist, notes that an old wooden garage can be surprisingly good at moderating humidity, while a modern brick garage with an ill-fitting up-and-over door can offer poor protection. What matters most is how well the building keeps out rain and draughts, and whether the floor lets moisture rise through it.

Before you rely on a garage, measure it. A hygrometer costs little and tells you what the air is actually doing. If the humidity regularly sits above about 60%, a dehumidifier in a reasonably sealed space is the usual answer. Our damp and condensation page explains how to choose and use one, and how to deal with a damp floor.

A carport

A carport keeps rain and snow off the car but does not seal it from damp air, so the car is still exposed to condensation and wind-blown wet. A breathable outdoor cover helps. A carport is better than open ground, but it is not a substitute for a dry garage over a long lay-up.

Outdoors under a cover

Keeping a classic outdoors through a British winter should be a last resort. Even a good cover leaves the underside exposed to damp air, and a cover that is not breathable, or that is allowed to flap in the wind, can do harm of its own by trapping moisture or rubbing the paint. If there is no alternative, use a multi-layer outdoor cover that is breathable, fits well and is strapped so that it cannot move, and take it off to air the car on dry days. Never use plastic sheeting or a tarpaulin.

Airflow enclosures

An airflow enclosure, sometimes called a car bubble or storage bubble, is a plastic envelope that zips around the car while fans keep air moving through it. Moving air helps to prevent condensation forming on the car. Indoor versions sit in a garage; outdoor versions are built to stand weather. Both need a constant power supply to work, so think about what happens in a power cut, and remember that an enclosure moves the surrounding air through it rather than drying it. In a damp building, a dehumidifier is still needed. The damp and condensation page covers enclosures in more detail.

Commercial storage

Specialist classic car storage firms keep cars in dehumidified buildings, often with battery care and regular checks included. If you are considering one, ask:

• What humidity is the building kept at, and how is it measured and recorded?
• How are cars secured, and what fire detection and suppression is there?
• Is my car insured while it is there, and by whom? Does the firm's own insurance cover my car, or must I keep my own policy?
• Who can move or start my car, and will they drive it?
• How is the battery looked after?
• How much notice do I need to give to collect the car, and what are the opening hours?
• Can I visit, and will I be told about any damage or rodent activity?

Get the answers in writing, and visit before you sign.

Tell your insurer where the car is kept

Classic car policies often carry conditions about where the car is kept overnight. If you move the car to a different garage, a storage firm or a relative's barn, tell your insurer first.

The right preparation depends on how long the car will stand.

• A few weeks. Keep the battery charged, leave the handbrake off, keep the garage dry and check for mice. Little else is needed.
• A winter. Follow the full winter lay-up routine: fresh oil, coolant check, fuel decision, tyres, battery, rodent proofing, cover and paperwork.
• A year or more. Longer storage raises bigger questions about fuel, which ages and can leave deposits, and about seals, brake hydraulics and tyres. The FBHVC recommends replacing ethanol petrol with ethanol-free petrol for an extended lay-up, and draining the carburettor float bowls if ethanol-free petrol cannot be found. A detailed page on long-term storage is in preparation.

A car that is off the road must either be taxed and insured, or declared off the road with a Statutory Off Road Notification (SORN). GOV.UK says you must insure and tax your vehicle if you do not have a SORN, and the DVLA can fine you £80 automatically for having neither.

• Historic vehicles built before 1 January 1986 can be taxed in the historic class, which costs nothing, but they still have to be taxed. Because the tax is free, the only legal saving from a SORN on a historic car is that it no longer needs insurance.
• A SORN does not need renewing. It ends when you tax the car again, or when you sell, export or scrap it.
• A car with a SORN must not be used or kept on a public road. The only exception is driving it to or from a pre-booked MOT or other test.
• Laid-up cover. Many classic insurers offer laid-up cover for a car with a SORN, which typically protects against fire and theft but not driving. Without any cover, a stored car is uninsured against fire, theft and damage, so most owners keep some cover in place.

Our law and security section explains historic tax and MOT exemption in full, and getting your car home covers taxing and insuring a newly bought car.

• Damp and condensation: relative humidity, why garages sweat, dehumidifiers, floors and covers.
• Mice and rats: how they get in, the damage and health risks, and which deterrents, traps and poisons work.
• Winter lay-up step by step: everything to do before, during and after a winter off the road.
• Winter lay-up checklist: a printable A4 tick-list.
• Storage pages on our sister sites, written for particular cars: Triumph Stag: storing your classic car, MG T-Series: winter storage, Jaguar E-Type: winter storage and lay-up

Where to keep a classic (in detail); car covers and airflow bubbles; long-term storage; starting a car after storage; recommissioning a long-stored car; fire safety in the garage; garage security; moving a classic; a printable spring recommissioning checklist.

For looking after a car while it is in use, see owning a classic. If you have yet to buy one, ask yourself where it will live before you bid: see thinking of bidding?.