Our units aren't heated, cooled or climate-controlled, so the temperature inside isn't regulated and will follow the seasons to some degree. We describe them as clean, dry and secure, but we don't control or publish the temperature or the humidity inside them at any site. The three most common seasonal problems in storage are these: damp, when temperatures swing and moisture settles on cool surfaces; water left inside things, which can freeze; and summer warmth, which softens candle wax and, over years, speeds the ageing of photographs and papers. So drain your washing machine, make sure everything goes in clean and dry, keep things off the floor with air around them, and give heat-sensitive things the coolest, most sheltered spot you have. The table below covers the common items one by one.
What our units are, and what you can't do in them
We don't have units with thermostats or humidity control, at any site. You can't change that yourself either: our terms don't allow portable heaters in a unit at any time (clause 19), and there's no power in the unit to run anything (see do storage units have electricity?).
Most of our units are inside our buildings. At Chipping Norton, Shipston-on-Stour and Warminster we also rent outdoor steel container units. Our booking system lists the Chipping Norton containers as insulated against condensation. Our Shipston-on-Stour containers are described the same way. We don't publish that detail for Warminster's container, so ask us about it before you book. We don't publish summer temperatures for any container either, so if you're storing heat-sensitive things, ask us before you book a container. If you're choosing between an indoor unit and a container for a winter stay, call us on 0800 2545585 and we'll talk through the site, and our guide on condensation in container units covers what to do inside one.
For context, the Met Office puts the UK's long-term outdoor average at 4.09°C in winter and 14.59°C in summer (1991 to 2020). Those are outdoor averages across whole seasons, not temperatures inside a unit, and individual days run colder and warmer. We don't publish temperatures for our units or containers.
What cold and warmth actually do
Cooling air makes damp
The Canadian Conservation Institute explains that when warm air is cooled, its relative humidity climbs, which is how damp appears where warm, humid air meets cool spots. It puts the practical boundary for damp at 75% relative humidity, above which mould can discolour and break down leather, textiles and paper. GOV.UK describes condensation damp the same way: moisture cooling and settling on the colder parts of a building. That is why damp packing and a cold floor are the two things to avoid.
Swings move wood
The same guidance explains that veneer can buckle when humidity rises, as the veneer swells and its glue softens, and can then set out of shape when the air dries again. Solid wood moves too: the Western Australian Museum's collections care manual says cold, damp conditions make wood swell and warp, hot, dry conditions make it shrink and crack, and large, rapid swings in humidity do the most damage.
Water freezes
Bosch's washing machine instructions warn against placing a machine anywhere liable to frost: residual water inside can freeze and damage it, and frozen hoses can crack or burst.
Cold makes some things brittle
Conservation guidance notes that some materials, such as acrylic paint layers, go glassy in the cold, and the main risk is that they crack when handled cold. For oil paintings or anything valuable, see our guide to storing paintings and artwork.
Warmth speeds slow ageing
For photographs and papers, the conservation rule of thumb is that each 5°C cooler roughly doubles an object's lifetime. A warm summer won't ruin a box of documents in one season, but over several years of storage the difference adds up. Candle suppliers give a quicker example: heat softens wax and warps candle shapes.
Item by item
| Item | Winter | Summer | What to do |
|---|---|---|---|
| Washing machine, dishwasher | Water left inside can freeze and crack hoses or parts | No extra risk once it's drained | Drain every drop before it goes in (your manual shows how), and leave the door open to dry |
| Fridge, freezer | Moisture left inside will smell | Same | Defrosted, dry, door open: see storing a fridge or freezer |
| Phones, tablets, laptops | Apple says store iPhones and iPads between -20°C and 45°C, and use them between 0°C and 35°C | Same range | If it's been below 0°C, let it warm up before you switch it on. For a laptop or any other make, check its manual for storage temperatures. Our guide to storing electronics safely covers packing |
| TVs and screens | Sony's instructions say moving a TV from a cold place to a warm one can cause condensation inside, giving a blurry picture or poor colour | Same care after any sudden change in temperature | Once it's home, leave it switched off for a few hours before you power it on |
| Vinyl records | The Library of Congress says widely fluctuating temperature or humidity shortens the life of all recordings | Same | Stand them upright, on edge, never flat, with full-height dividers or packed tight so they can't lean |
| Candles | Humidity can make some waxes frost or sweat | Heat softens wax and warps shapes | Pack pillar candles lying flat, wrapped in tissue. Ask us before storing candles in quantity, such as shop stock: our terms don't allow combustible substances (clause 18(c)) |
| Wooden and veneered furniture | Cold and damp can make solid wood swell and warp, and humidity swings can lift veneer | Hot, dry air can make wood shrink and crack | A dust cover, raised off the floor on blocks so air can circulate, and not touching the walls. The museum manual says never to put wooden objects in direct contact with outside walls |
| Leather sofas and chairs | Above 70% relative humidity, mould can grow on leather | Very dry air (below 40%) can make leather brittle | Clean it first, cover it with a cotton (calico) dust cover, keep it where air can move, and look it over when you visit |
| Framed pictures and mirrors | Damp, and cracking if paint layers are handled while cold | Same | Stand them upright, with board between frames and padding underneath, raised off the floor, and not leaned against outside walls. See storing paintings and artwork |
| Clothes, bedding, soft furnishings | Damp, not cold, causes the musty smell | Same | Clean and fully dry going in: see stopping clothes going musty |
| Photographs, papers, documents | Damp is the risk | Warmth speeds slow ageing over years | Boxed and off the floor. Our terms don't allow deeds and securities (clause 18(i)) or "items which are unique in nature and/or where the value to You cannot be assessed on a financial basis" (clause 18(j)); if you're unsure whether something counts, ask us before you book |
| Paint, gas, solvents | Can't be stored at all (clause 18(c)) | Same | Keep them at home, or dispose of them properly |
If your list includes fine art, musical instruments or other sensitive pieces, our honest guide to climate-controlled storage goes through them one by one.
Before a winter or summer in storage
- Get the water out. Drain washing machines and dishwashers, empty and dry fridges, and don't pack anything wet.
- Pack on a dry day if you can, so moisture doesn't go in with your things.
- Keep things off the floor on a pallet or a layer of hard boxes, and leave a gap at the walls so air can move.
- Handle painted and delicate pieces gently in a frost. As above, some materials turn brittle in the cold and crack when handled.
- Look in now and then. Our terms advise you to inspect your unit from time to time (clause 26). Access is 6am to 10pm, seven days a week, so a check after a cold snap or a hot spell is easy. If you're away, you can share access with someone who can check for you.
If you're a business storing stock, the same rules apply: read the storage temperatures on your product labels or supplier sheets, and store what they allow.
Who carries the risk
Under our terms, you must make sure the unit suits what you're storing (clause 26), goods are stored at your own risk (clause 30), and they must be insured, through our contents protection or your own policy (clause 31). The RSA policy you can take out through us doesn't cover atmospheric or climatic damage, so preparation is your real protection against damp and frost. Our page on who is responsible for mould explains the terms in full.
Getting a unit
If you're storing through the winter or over the summer, get a price online or call us on 0800 2545585. If you're not sure whether something on your list will cope, ask us before you book.
Related questions