You book a storage unit, load it once, and assume the job is done. Then your plan shifts. A move expands, a business delivery lands early, or you clear more space at home than expected. A storage unit that felt fine on day one can start costing you in time and effort. This guide shows how to spot the moment your unit stops fitting, how to decide if the problem is layout or volume, and how to switch sizes with less stress.  At Spacebox  Self Storage our flexible contracts make it easy to change unit size at any time (if available), so you can adjust without feeling locked into your first choice. 

Know when a size change makes sense

• Do a real access check after you add anything new
  Walk in, reach one item you expect to use again, and put it back without moving stacks. If you keep “temporary piles” near the door or you have to shift boxes to reach basics, access becomes the problem before volume does.
• Treat a blocked doorway as your first red flag
  If the first metre inside the unit fills up, every visit turns into lifting and re-stacking. Your unit starts working against you, even if the overall volume still fits.
• Watch for “unstable stacking” as a size warning
  If you stack higher because you lose floor space, you create risk and frustration. A unit that forces awkward stacking is not the right fit for your current load and access needs.
• Spot overbooking early, not months later
  If most items sit along one wall and you keep a large empty zone you never use, you pay for space that does not support your plan. The right size matches what you store, not what you fear you might store later.
• Link the decision to your reason for storage
  Moving house needs different access than long-term storage. Business stock needs different access than seasonal luggage. Decide what you need to reach first, then size around that access.

Decide if the issue is layout or volume

• Fix layout first when your items “fit” but you cannot reach them
  Create three zones: a clear door zone, an aisle you can walk down, and a back zone for items you do not need often. If a repack restores access, you may not need a larger unit.
• Upsize when an aisle becomes impossible to keep
  If you cannot keep any walk space without crushing items together, a larger unit gives you working room. Space becomes usable again when you can move without dismantling stacks.
• Downsize when your plan changes and you no longer need buffer space
  If you stored items for a short move window and now only keep a smaller set, you can cut the unit size and still keep access.
• Use “access frequency” as the deciding factor
  Items you need weekly need a front zone. Items you need monthly can sit mid-unit. Items you may not need at all can go to the back. If your current size cannot support this, change size.

Estimate the right size with less guesswork

• List by “item type” because shape decides space
  Count boxes, then list bulky items (chairs, suitcases, small appliances) and awkward items (lamps, long bags, framed items). Awkward shapes steal aisle space faster than boxes.
• Mark what needs access so you size for movement, not just volume
  If you need to reach tools, seasonal stock, documents, or travel bags, you need aisle space. A “fits exactly” unit often fails because it removes walk space.
• Build a safe stacking plan before you size up or down
  Put heavy items low, keep fragile items in a front-top area, and keep labels facing out. If you cannot stack safely without blocking access, the size is not working.
• Allow a small “handling zone” so switching stays manageable
  Leave a small working area near the front where you can put items down during visits. If you have to unload outside the unit every time, day-to-day use becomes harder.

Request a unit size change without chaos

• Confirm availability first, then move once
  The main stress comes from moving before the new unit is ready. Reserve the new size, confirm access details, then transfer in one session.  Remember size change depends on availability. 
• Transfer in a fixed order so nothing goes missing
  1. Clear the floor first (heavy boxes, storage tubs).
  2. Build your back zone next (items you will not need soon).
  3. Create your aisle early, not at the end.
  4. Move “access items” last so they end up at the front.
• Use one simple tracking method during the move
  Write categories on a short list (boxes, kitchen, documents, stock, luggage). Tick off each category as it enters the new unit. This prevents the “did we move that?” loop.
• Keep the old unit stable until the new one is ready
  Avoid unpacking mid-transfer. Move in batches, close each batch, then start the next. That keeps your head clear and your unit usable during the switch.

Downsize and upsize with confidence

• Downsize when you pay for space you do not use
  Remove low-value categories first (duplicates, packaging, items you no longer plan to keep). Repack into consistent box sizes, then rebuild your zones in the smaller unit so you keep access.
• Upsize when access becomes the daily problem
  If you lose your aisle and every visit turns into moving stacks, upsizing can save time and reduce effort. Use the extra space to rebuild the layout: front access zone, clear aisle, back long-term storage.
• Use the size change to reset your system
  Take one quick photo per zone after you finish. You can find items later without pulling stacks apart, and your unit stays usable for the rest of your storage period.

Change your unit size with ease