Preservation and Restoration: How the World Keeps Its Windmills Turning
A windmill left to itself does not decay slowly. Sails rot and collapse within decades; without sails the cap leaks; without a watertight cap the timber structure inside the tower deteriorates; within a century what was a working machine is a roofless shell. The survival of working windmills is not an accident of climate or construction quality. It is the result of sustained organised effort by a network of specialist bodies that has been running, in some countries, since the 1920s.
TIMS: the international network
The International Molinological Society — TIMS, from the Dutch molinologie — is the closest thing to a global professional body for windmill and watermill preservation. Founded in 1965, it holds symposia every four years (alternating between European and non-European hosts) that bring together mill historians, engineers, millers, and heritage administrators from across the world. TIMS publishes the journal Transactions of the International Molinological Society and maintains a database of mill types, engineering conventions, and restoration standards.
TIMS does not own mills or fund restoration directly; its role is normative and scholarly — establishing what "correct" restoration means across different national traditions. This matters because the standards differ significantly between, say, Dutch institutional practice (which allows modern materials concealed behind traditional exteriors) and English SPAB-influenced practice (which insists on traditional materials throughout where possible). TIMS conferences are where those debates happen at an international level.
SPAB Mills Section, United Kingdom
The Society for the Protection of Ancient Buildings has run a specialist Mills Section since 1931, which makes it the oldest dedicated mill-preservation body in the world still operating. The SPAB Mills Section trains volunteer mill stewards through a network of working mills, maintains technical guidance on restoration methods, and campaigns for the retention of working status as the criterion for heritage investment.
The SPAB position on mill restoration is characteristically conservative: it holds that mills should be preserved in the most authentic state achievable, using traditional materials (not fibreglass sails, not reinforced concrete towers), and that a mill preserved as a static monument has been compromised. The Section organises National Mills Weekend, held on the second weekend of May each year, during which member mills across the UK open to the public with machinery running. It is the single best opportunity to visit a working English or Welsh mill and usually involves around 200 sites nationwide.
De Hollandsche Molen, the Netherlands
De Hollandsche Molen (The Dutch Mill Society) was founded in 1923 and is the oldest national mill-preservation body in existence. It was established precisely because the mechanisation of the Dutch milling and water management industries in the late nineteenth and early twentieth centuries was rapidly rendering windmills obsolete, and several prominent Dutch cultural figures recognised that the country's stock of mills would collapse unless they were actively maintained.
The Society now has around 9,000 members and is involved in the technical oversight of approximately 1,200 registered mill monuments in the Netherlands. Its most visible activity is the coordination of the Dutch National Mill Day (Nationale Molendag), held on the second Saturday of May, when mills across the country raise their sails and are open to visitors. Attendance is typically around 750,000 across the full weekend. The Society also runs training for the Molenaar (miller) qualification — the vocational certification required to operate a heritage windmill in the Netherlands, which takes roughly two years of part-time study at an operational mill.
Stiftung Mühlenforschung, Germany
Germany's mill-research and preservation landscape is more fragmented than the Dutch model, reflecting both federal governance structures and the greater diversity of mill types across the country. The Stiftung Mühlenforschung (Mill Research Foundation), based in Schleswig-Holstein, coordinates academic research into mill history and supports documentation projects across Germany and neighbouring countries.
The most prominent public event in German mill preservation is the Deutsche Mühlentag (German Mill Day), held on Whit Monday (Pfingstmontag) each year. It involves around 1,000 mills across Germany and several hundred more in Austria, Switzerland, and German-speaking communities elsewhere in Europe. The event is organised by the Deutsche Gesellschaft für Mühlenkunde und Mühlenerhaltung (DGM), which also maintains a national register of surviving mills and provides technical advice to mill owners.
The working-mill criterion
Across all the major preservation organisations, a central debate recurs: should the goal of restoration be a working mill — one that can grind grain, pump water, or perform its original function — or is a well-preserved immobile structure an acceptable outcome?
The arguments for working-mill restoration are practical as well as aesthetic. A mill that turns exercises all its mechanical components, keeping timbers flexed and bearing surfaces in use; a static mill has dry rot where loaded timbers once flexed, and seized bearings where rotation once kept them greased. Several English mills restored as static monuments in the 1960s and 1970s have since required expensive remedial work precisely because the machinery was not kept moving.
The counter-argument is cost. A fully working restoration — new wooden sails, properly dressed millstones, a functioning brake mechanism, a skilled miller to operate it — costs vastly more than a weatherproofed shell. Grant bodies and local councils often fund the cheaper option. The SPAB and De Hollandsche Molen both argue, with some evidence, that working mills attract more visitors, generate more educational value, and produce more community engagement than static monuments; but funding systems rarely capture those benefits in the restoration-cost calculation.
Trust funding and the volunteer system
In the United Kingdom and the Netherlands particularly, many working heritage mills are managed by local trusts — charitable bodies established specifically to maintain a single mill or a small group. Trusts typically combine public grant funding, visitor donations, flour sales, and volunteer labour. The volunteer structure is essential: skilled volunteer millers operate machinery on demonstration days for no pay, reducing running costs to a level that donations and grants can cover.
The Saxtead Green Post Mill (English Heritage), the Cranbrook Union Mill (Cranbrook Mill Trust), and the Heage Windmill (Derbyshire Historic Buildings Trust) are examples of this model. Each depends on a small group of trained volunteer millers who operate the machinery on open days and maintain basic mechanical competence year-round.
Finding preserved and working mills
The map covers the full range of mill preservation status — from UNESCO World Heritage ensembles to single local-trust mills open one Sunday a month. Use the map to find mills near you, then check directly with the mill or its managing trust for opening schedules and whether the machinery will be running. The difference between a turning mill and a locked tower is the difference between an experience and a photograph of a door.
Mill preservation is more precarious than it looks from the outside. The buildings that survive are there because specific people organised and funded and trained and turned up on cold mornings to grease the bearings. That effort is ongoing, and supporting it — by visiting, donating, or joining a local mill society — is what keeps sails turning.