Caston Tower Windmill
The restoration of the cap at Caston Tower Mill
The following is a brief history of Caston Mill, its working life and ongoing restoration including the works to be undertaken commencing 2021.
The working history of the Mill
Caston Tower Windmill is a grade II* listed tower mill at Caston, Norfolk, England which is under restoration. The mill is also a scheduled monument and was listed in 1957.
The tower mill was built for Edward Wyer in 1864. Edward Wyer's father John Wyer, had previously been miller and baker at Caston, running the postmill that was later demolished by Edward to make way for the tower mill built on the same site. William Wright, a builder from Caston, constructed the mill and granary, and millwright Robert Hambling of Dereham, whose name appeared on several of the castings, installed the machinery.
Edward Wyer ran the mill until his death on 5 July 1897. Wyer's son James took over the mill and ran it until 1910 when he retired. In that year, Wyer's brother-in-law Benjamin Knott took over running the mill. Knott ran the mill until 1940, latterly in partnership with his son James. During Knott's tenure, a Hornsby oil engine was installed in the granary, driving a further pair of millstones.
Milling for flour ceased around the beginning of the First World War, but the mill continued to be used under sail for grinding animal feed until the late 1930’s. In 1940, the mill was sold to James Bilham, who used the engine driven millstones for milling, and removed the two pairs of Derbyshire Peak millstones from the windmill. An electric mill was eventually installed on the ground floor to grind meal for the duck farm operated on the site until James Bilham's death in 1967.
Numerous repairs were undertaken throughout the working life of the mill. New stocks were fitted in 1915. In the early 1930’s these were replaced, and new sails fitted following a catastrophic failure. The tower was re-tarred in 1936. After the mill ceased being used under sail around 1940, no further maintenance was undertaken and in 1959, James Bilham asked Smithdales of Acle to remove the decaying cap, but this work wasn’t undertaken and the cap remained in place.
A Technical Overview of the Mill
The six-storey tarred brick tower is 55 feet high to the curb, 26 feet outside diameter at the base and 17 feet outside diameter at the curb, with staging set around the second floor.
A two-storey granary is built and attached to the south side of the tower.
A Norfolk boat shaped cap with gallery, petticoat and 6 bladed fan run on a cast iron curb on the top of the tower.
The four patent sails each had 8 bays of 3 shutters and 2 bays of 2 shutters, struck by lever and these powered the right-handed 4ft underdriven stones, comprising of two pairs of Derby Peak stones and one pair of French burr stones.
A brick-built workshop was added in the 1970’s to the west side of the granary from where Lennard & Lawn (Millwrights) Ltd. operated.
Restoration work by John Lawn
Norfolk millwright John Lawn bought the mill in October 1969 from James Bilham's widow, with the intention of restoring it to working condition.
When John Lawn bought the mill, the sails had lost their shutters, and the fantail had mostly disintegrated. The mill machinery was still in working order and John had the sails turning in the early 1970’s. However, he was also involved with the restoration of other mills in conjunction with the Norfolk Windmills Trust, and he never succeeded in restoring his own mill to working condition.
By 1975 the adjoining granary had been converted to residential use. The mill and workshop was housing the business of Lennard & Lawn (Millwrights) Ltd. and consequently the restoration of Caston Mill took place on an ad hoc basis. All but one of the windows (dust floor, north facing) in the tower were replaced during this period. The granary was re-roofed during this same period.
By the late 1970’s the cap ribs and weather boarding had collapsed and on 23rd November 1983 the cap and sails were removed for replacement as part of restoration work. The cap was lifted off and placed in front of the granary where it was steadily rebuilt. Two new shears delivered in 1984 formed the basis of the rebuild.
Work commitments and illness delayed repairs, however friends and family continued to work on the cap following his death in 1999, and it was reinstated in the year 2000.
Subsequent restoration work
John Lawn’s widow Sylvia sold the Mill and granary in 2012. The new owner retarred the tower, whitewashed the inner walls on the ground floor and first floor, and replaced the floorboards on the ground floor and first floor in the mill.
We purchased Caston Mill in Nov 2015.
The corrugated workshop roof was replaced in 2017.
All but one of the replacement windows fitted by John Lawn in the lower three floors of the tower have been replaced with new frames and lift out casements made as copies of the one remaining original window on the dust floor.
The 1970’s windows to the south end of the granary were replaced.
Fascias and top plate repairs to the east of the Granary, and gable end timbers were repaired. Rainwater goods to the east were replaced in 2016.
A technical description of the Cap
A Norfolk boat-shaped timber construction cap, with its gallery and petticoat, are built on two 12” square oak shears, that run on castors on a cast iron curb ring fixed to the top of the tower. When in operation, the cap is turned to wind by the 6 bladed left-handed fan (fly) mounted on a frame to the rear staging of the cap driving a worm gear operating on a rack cast to the outside of the curb ring.
Present condition of the Cap
When the main shears were replaced, the shear laps were also put back on. Shear laps are normally only used to extend the life of the original shears. The last restoration of the cap therefore faithfully copied a previous repair. The shear laps have shakes that have allowed water ingress into the interface with the shears on the outside of the cap.
The cap was last painted in 1999 before being replaced. This was with a sandtex like product which has been peeling and allowing water ingress into multiple joints and board ends.
The cedar weatherboarding on the breast of the cap takes the brunt of the prevailing weather. The cap valley where the side weatherboarding meets the breast boards was rebuilt using sealant that has failed and allowed water ingress into the corners by the head ribs. This has caused wet rot in one corner of the cap. There are a few holes from bird damage.
The fan stage boards, and gallery boards, have decayed and partially disintegrated. The Fan ledger is in very bad condition with wet rot through most of the section. The Principal ledger has decay to the upper surface.
The Worm Hangers have cracked and rotted on their lower edge and much of the timber has fallen away up to and above the worm shaft bearing.
Water running in through the cap valley has caused decay in the left-hand end of the weather beam and to a lesser extent to the opposite end.
The planned cap restoration 2021
A temporary flat roof, boarded, with an EPDM membrane is currently being constructed in front of the granary.
When weather conditions are favourable to the crane operator, the millwrights will remove the centering wheels and ensure the safe removal of the cap to ground level on in front of the granary. The temporary cap will be lifted and secured using ratchet straps and L brackets under the keep flange of the curb.
Over the next few months, the following works are planned:
Shear laps - slacken fastenings and lift to allow inspection for any soft areas of main shears.
Repair shakes and carry out other localised repairs.
After repair work to surrounding timbers has been completed, refasten, and apply lead capping.
Shears - inspect for any soft areas of main shears beneath shear laps. Trim back decayed
exposed area beneath the mill cap breast and replace missing petticoat boards in this area.
Fan ledger - to be replaced whilst shear laps are lifted.
The Principal ledger - repairs to upper surface.
Worm hangers - to be replaced. Lead capping applied to upper cut ends. Renew worm shaft bearing surfaces.
Fan staging - to be replaced.
Fan frame - cosmetic repairs as required. Inspect for any soft areas and decay and carry out localised repairs if required.
Weather Beam - the top surface at the ends to be cut back to sound material before scarfing, laminating, and dowelled repairs.
Head ribs - cut back to sound material before scarfing and laminate repairs to create a secure joint into Weather beam.
Puncheons - remove remains of rotten Gallery boards before inspecting for soft areas and decay. Carry out repairs to upper surface. Leadwork applied to exposed upper flat surfaces.
Gallery staging - to be replaced.
Cap valley retrofit - cap boards to be eased to allow the installation of lead soakers.
Cap boards - localised scarfed repairs to damaged end of boards and to repair holes created by bird damage.
Petticoat boards - replace missing boards and undertake any localised scarfed repairs.
Inspect condition of original timbers including Tail beam, Sprattle beam, Header stock, Header stud and rib circle. Brush off loose debris and apply a water-based preservative.
Prep and paint cap - all the external wooden surfaces of the cap will have the existing paint removed before being repainted with a white opaque stain. Where originally painted, metal components will be cleaned, primed with red oxide, and repainted with a black enamel.
Following restoration of the cap and when weather conditions are favourable to the crane operator, the cap will be replaced.