How do I store books so they do not go musty or warped?

Books are more fragile than they look and they fail slowly, so the damage is usually done before anyone notices. Three things do nearly all of it: moisture, which causes the foxing and the musty smell and eventually mould; ultraviolet light, which bleaches spines and embrittles paper; and mechanical stress from being packed the wrong way, which warps boards and breaks hinges. All three are cheap to avoid and impossible to reverse.

Step by step

1. Keep them in the house, not in an outbuilding.Lofts cycle between extremes of heat and cold, garages and sheds are damp, and both attract insects and rodents. Books stored in either are usually unsalvageable within a few years. This is the single most important rule here.
2. Shelve upright, supported, and not crammed.Upright with a bookend so nothing leans, because a leaning book warps its boards permanently. Snug enough to support each other and loose enough to remove one without pulling on the headcap, which is what tears spines.
3. Keep shelves off external walls and allow air behind.A bookcase flat against a cold external wall traps still, cool air and is a classic mould site. A couple of centimetres of gap, and avoiding the coldest wall entirely, prevents it.
4. Keep them out of direct sunlight.Ultraviolet fades spines within a single summer on a south-facing wall and makes paper brittle over years. A blind, a UV film on the window, or simply choosing a different wall.
5. Aim for stable, ordinary indoor conditions.Books tolerate normal living conditions well. What they do not tolerate is repeated swings between damp and dry, which is what causes cockling and loosens bindings. Stability matters more than any particular figure.
6. Lay very large or heavy books flat.Atlases, art books and anything oversized should lie flat, no more than two or three high. Standing them upright lets the text block sag away from the spine under its own weight.
7. Box them properly if they must be stored.Small crates so they can be lifted, clipped lids against dust and insects, packed flat or spine-down but never fore-edge-down, which drags the text block out of the case. Fill gaps so nothing shifts.
8. Add a desiccant and check occasionally.A silica gel pack in each sealed crate absorbs the moisture that was already in the room when you sealed it. Open and look once a year — mould and insect damage are both far cheaper to catch early.
9. Deal with a musty smell early.Air them open, spine down and pages fanned, in a dry room with moving air, for several days. Baking soda or charcoal in a sealed box with the book, not touching it, helps. Persistent mustiness usually means mould, which means the storage was wrong.
10. Treat leather and antiquarian books differently.Leather bindings need stable humidity above all and can suffer red rot in dry heat. Do not oil or treat a valuable binding on general advice; get one specific piece of advice for that book.

Keeping on top of it

• Dust the top edges with a soft brush, top edge down and away from the text block (Twice a year)
• Check boxed books for damp, mould and insect damage (Annually)
• Check behind bookcases on external walls for condensation or mould (Each winter)
• Replace or dry out desiccant packs in sealed crates (Annually)

Questions people ask