4 C O N T E X T 1 0 8 : M A R C H 2 0 0 9 Is it a boat jack? Material matters Hoop iron Hoop iron can be found quite commonly in Victorian buildings. Its use is described in JP Allen’s Practical Building Construction (1893) and many other books of the period. Allen wrote: ‘Hoop-iron bond, which has superseded the use of longitudinal bond-timbers, consists of long strips of wrought-iron, about 1 1/8 inches by 1/16 inch laid and built in along walls, between courses, in rows at every two or three feet in height above head, and below sills of window, and turned at the ends up joints to assist in preventing rupture of the brickwork horizontally from unequal settlements. It is often specified to be tarred and sanded before been built in.’ Hoop iron is not always easy to spot. Generally the telltale signs are minor horizontal cracks, internally or externally.With render, rust staining can sometimes be seen. The hoop iron is often laid two lines in a nineinch-thick wall. The outer one, being closer to the elements, is more prone to corrosion. This can lead to jacking the brickwork upwards and to a clear gap in the mortar course. The greater the gap, the more the water ingress and the greater the corrosion rate. In most cases hoop iron can be left alone, with the mortar raked out and re-pointed to slow the rate of corrosion.Where the damage is excessive, the hoop iron will need to be cut out by removing stretchers, raking out the mortar to the headers, ‘snipping’ the iron, and piecing back the stretcher and re-pointing. This is an expensive and time-consuming task. The inner band can often be left, as it is better protected from the elements, but some hairline cracking to finishes should be expected. Cathodic protection could be considered, although I have not yet had to attempt this. Ed Morton, member of the IHBC technical panel I recently came across this curious item in an antique shop in Ashbourne, Derbyshire. The object is constructed of a solid block of timber (approximately 30cm x 60cm x 15cm) incorporating an extending iron foot on a simple ratchet system. I recall seeing a similar item many years ago in a barn full of curiosities collected by an elderly retired water bailiff who lived next to the River Severn in Gloucestershire. He explained to me at the time that he thought it was a jack used to lift heavy objects such as boats under construction. He also mentioned the use of the device for jacking timber-framed buildings, presumably for the purposes of repair. A similar item is shown lying in the foreground of John Constable’s 1817 painting Boat Building near Flatford Mill. This reinforces the boat jack theory. It would be useful to hear from anyone who knows more about this object. Julian Bagg, coordinator, IHBC technical panel Let us know If you know of any unusual or rarely documented techniques, artefacts or materials, Material matters would like to hear from you. Contact Julian Bagg, technical panel coordinator at technical@ihbc.org.uk. Hoop iron course evident on careful inspection Staining indicates hoop iron Hoop iron extending out of demolished section of wall
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