Inside Whisky Warehouses: Dunnage, Racked and Palletised

One cask can lose alcoholic strength while another, higher in the same warehouse, gains it. Position matters: the air around the wood helps shape maturation. To tell warehouse types apart, start with the casks themselves. Dunnage and racked stores hold them on their sides; palletised stores hold them upright on pallets. The building and a cask's position can create different conditions for maturation, but warehouse type alone is not an established guide to whisky quality. [1][2]

In short

• In 2015, the Scottish Building Standards Division described pallet stacking as the predominant storage method in Scotland. [5]
• Kilchoman describes lower casks in tall stores as cooler and more humid than upper casks. [1]
• A cask can gain or lose alcoholic strength during maturation, depending on the conditions around it. [2]

Warehouse types at a glance

The storage system defines the type, not the building's height. These published arrangements vary: Kilchoman describes racked stores reaching 12 or more casks high, while the Whisky Professor's trade account includes dunnage stows on more than one storey. There is no single height specification for each kind of warehouse. [1][2]

Dunnage: earth floors and shallow stacks

Thick walls, an earth floor and shallow stacks of casks give dunnage warehouses their familiar place in accounts of traditional Scotch maturation. Kilchoman describes low buildings with casks lying in stows no more than three high. The Whisky Professor adds that walls may be stone or brick, with a slate-and-timber roof and floors of earth or cinders without a damp course. [1][2]

For Kilchoman, the attraction is the atmosphere inside: humid, with little seasonal variation in Scotland. The distillery says this steadiness gives casks across its warehouses a consistent rate of maturation. It reports maturing all its casks in dunnage warehouses on Islay's west coast, explaining its choice through the conditions it values for its whisky. [1]

The layout also shapes the daily work. Kilchoman says the earth floor and low ceiling prevent forklift use. Dunnage is therefore more than a tall storage system reduced to a few rows: its construction affects both the climate around the casks and how they can be handled. These practical restrictions are part of understanding the system, distinct from Kilchoman's stated climatic reasons for choosing it. [1]

Racked warehouses: casks on steel frames

Steel frames let racked warehouses carry horizontal casks far above the shallow stows of dunnage. The Whisky Professor dates this warehouse type from the 1950s and describes stacks eight or 12 casks high. Kilchoman describes concrete floors throughout, with racks sometimes reaching 12 or more casks high. [1][2]

The familiar American rick house also holds barrels horizontally, supported on ricks. Whisky Advocate describes barrels usually stacked three high within those ricks, while most modern rick houses have about seven storeys. These measurements describe different things: three barrels in a stack does not mean three floors in the building. [3]

Kentucky itself offers several approaches. Whisky Advocate's 2020 account describes Four Roses using single-storey rick houses, Michter's building four-storey warehouses and using heat cycling, and Woodford Reserve adding palletised warehouses beside its rick houses. Calling a building an 'American warehouse' says little about its particular arrangement or the maturation conditions inside. [3]

Palletised warehouses: upright casks moved together

Stand the casks upright and a forklift can move several at once. That is the practical change behind palletisation. Whisky Advocate describes typically four to six barrels on a pallet; Kilchoman describes pallets often stacked six or eight layers high. Orientation and handling change together. [1][3]

Palletisation has a central place in Scottish maturation. In its 2015 correspondence on maturation buildings, the Scottish Building Standards Division described free-standing or block stacking of wooden barrels on pallets as Scotland's predominant maturation storage method. That statement identifies a method, not a verified percentage of Scottish casks held in it. [5]

In a photograph of a tall store, look past the height to the casks. Those lying on their sides within frames are racked; those standing upright in groups are palletised. Height alone will not identify the system. [1][3]

Why position inside whisky warehouses matters

A tall warehouse can contain markedly different climates from bottom to top. Kilchoman describes lower casks as cooler and more humid, upper casks as hotter and drier, with greater evaporation loss of water. Its account also associates the concrete floors of racked and palletised buildings with relatively lower humidity than dunnage. [1]

The Whisky Professor gives illustrative summer temperatures for Scottish racked warehouses: upper casks might reach 20 °C (68 °F), compared with 12 to 15 °C (54 to 59 °F) below. For Kentucky rick houses, the same trade account gives possible upper-floor temperatures of 50 to 60 °C (122 to 140 °F), against 18 to 21 °C (64 to 70 °F) at the bottom. These are published examples rather than operating targets. [2]

Humidity helps explain why strength can move in opposite directions within one building. The Whisky Professor explains that a lower cask can lose strength while a higher one gains it, because lower humidity favours water loss. For the fuller explanation of evaporation, see the angels' share; climate and maturation explores the wider climatic effects. [2]

Air does not necessarily circulate evenly, either. A 2025 University of Kentucky study of a new rick house reported air entering mainly through windows and ground vents, then moving along walkways. It found significant stagnant zones and little recirculation within the ricks. The study's abstract describes that building, rather than establishing an airflow pattern for every warehouse. [13]

The useful comparison is more precise than Scotland versus Kentucky. Conditions can differ between countries, between buildings and vertically within a single store. A cask's position adds information that an exterior photograph cannot supply. [1][2]

Does dunnage make better whisky?

Claim: Dunnage makes better whisky.

Verdict: Disputed.

What the record shows: Kilchoman favours dunnage for humidity and climatic stability. The Whisky Professor considers warehouse type a relatively minor factor and its effect on quality open to question. [1][2]

Evidence gap: Kilchoman's explanation of its choice is not a comparative trial of warehouse designs or their quality, and the sources checked provide no comparative sensory trial. [1][2]

Earliest known source: Not reliably established. The earliest source listed on the fact sheet is the Whisky Professor's account, dated 29 November 2018. [2]

Sources: Kilchoman, 11 February 2021, https://www.kilchomandistillery.com/?p=15306; The Whisky Professor, 29 November 2018, https://scotchwhisky.com/magazine/ask-the-professor/21776/do-dunnage-warehouses-create-better-whisky/.

Last checked: November 2026.

Traditional construction does not guarantee better whisky, just as a modern palletised building does not imply inferior whisky. Nor can differences between upper and lower positions reveal which individual cask a drinker will prefer. The stronger conclusion concerns conditions: warehouse descriptions explain the setting for maturation more securely than they predict the quality of the result. [1][2]

Read a producer's account with three questions in mind: how are the casks supported, where do they sit, and what evidence supports claims about the resulting whisky? Keeping those questions separate makes the description more useful. How whisky matures in oak supplies the broader context, placing the warehouse within the whole maturation process.

Safety and the warehouse environment

A maturation warehouse is also a place where large quantities of spirit are stored together. In Great Britain, the Health and Safety Executive's guide for assessing major accident safety reports for whisky maturation warehouses identifies pool fires, cask stack fires, warehouse fires and explosions among the scenarios considered. It lists lightning as a possible initiator and says safety reports must include the toxic effects of combustion products from wooden casks. [7]

Beyond the whisky remaining in a cask, evaporation has an environmental dimension. A Scottish Government review published in 2023 attributed over 90% of whisky-making emissions of non-methane volatile organic compounds, abbreviated to NMVOCs, to maturation. Its inventory put maturation emissions at 72,438 tonnes in 2020, across 124 identified sites with Scotch whisky storage for maturation. These are inventory figures, not a current warehouse count. [8]

Cask orientation, stack height, handling, internal climate and safety all belong in an account of warehouse design. The old stone exterior tells one part of that story. Inside, an upright pallet or a steel rack gives equally concrete information about how the casks are held and how the store operates. [1][2][3][7]

Where to go next

• How Whisky Matures in Oak: for the processes taking place inside the cask.
• How Climate Changes Maturation: for the wider relationship between weather and maturation conditions.
• The Angels' Share: Where the Missing Whisky Goes: for a closer explanation of evaporation and changing strength.

Sources

[1] Kilchoman Distillery. Why Choose Dunnage Warehouses?, 11 February 2021. Producer's account.
https://www.kilchomandistillery.com/?p=15306

[2] ScotchWhisky.com, The Whisky Professor. Do dunnage warehouses create better whisky?, 29 November 2018. Trade explanation.
https://scotchwhisky.com/magazine/ask-the-professor/21776/do-dunnage-warehouses-create-better-whisky/

[3] Whisky Advocate, T. Sachs. Whisky Barrel Storage 101: All About Warehouses, 11 June 2020. Trade reporting.
https://whiskyadvocate.com/all-about-whisky-warehouses/

[5] Scottish Government, Building Standards Division. Whisky Maturation Warehouses: Storage Buildings (Class 1), letter to Scottish local authority chief executives, reference A10277766, 5 February 2015.
https://www.labss.org/sites/default/files/00470202_whisky_maturation_warehouses.pdf

[7] Health and Safety Executive. PM/Technical/10, HID Safety Report Assessment Guide: Whisky Maturation Warehouses, March 2012.
https://www.hse.gov.uk/comah/assets/docs/whisky-maturation.pdf

[8] Scottish Government, prepared by Aether. Non-methane volatile organic compound emissions from malt whisky maturation: final report, 16 August 2023, sections 2 and 3.
https://www.gov.scot/publications/review-human-health-environmental-impacts-non-methane-volatile-organic-compound-emissions-malt-whisky-maturation-scotland-final-report-prepared-scottish-government-aether/pages/4/
https://www.gov.scot/publications/review-human-health-environmental-impacts-non-methane-volatile-organic-compound-emissions-malt-whisky-maturation-scotland-final-report-prepared-scottish-government-aether/pages/3/

[13] S. J. Schafrik, M. W. Long, Z. E. Wedding, B. M. Diddle and Z. Agioutantis. Reducing Product Loss Through Ventilation in Bourbon Maturation Warehouses. Sustainability, volume 17, issue 2, article 699, 2025. Abstract.
https://mdpi-res.com/d_attachment/sustainability/sustainability-17-00699/article_deploy/sustainability-17-00699.pdf

This piece is desk research based on the site's verified fact sheet and its cited producer accounts, trade reporting, official publications and research abstract, without a site visit or comparative tasting.

Last checked: November 2026