Gridirons, bargebeds and hards are a related group of structures found on the foreshore. They all provided a stable working surfaces on which vessels could be grounded at high tides. The three types await close definition, and more research is needed into both the archaeological examples and historical records. That's where you come in!

GridironThe term 'gridiron' (sometimes referred to as a 'block') refers to a fairly ad hoc structure built to allow a vessel to be repaired or broken up. The vessel is grounded on the gridiron, which normally consists of long timbers laid perpendicular to the river forming a rough 'grid'. The vessel is thus supported on the timbers, allowing work to be carried out at low tide.The Gridiron may be slightly raised in order to make the platform level and possibly to allow work beneath the hull of the vessel. Gridirons were usually constructed level, as opposed to slipways which would slope into the river to allow the vessel to be launched.

The gridirons were often built of re-used ships timbers and can provide a valuable source of information on the type of ships that were broken up in a specific location. Additional material such as nails or scattered ships' timbers may be found in association with the gridiron and may be related to the repair/breaking process.

BargebedA 'Bargebed' is another type of working surface. The term usually refer to a level platform adjacent to a wharf, jetty or river wall on which barges or other vessels could be grounded in order to be loaded and unloaded. Bargebeds were an expensive and usually well-constructed piece of foreshore engineering that may be linked to a specific on-shore building or industry

Bargebeds were usually constructed by initially building a substantial pile and plank revetment parallel to the river wall, behind which rubble and solid material was dumped to form the level platform on which the vessels would sit. This dumped material may contain artefacts which can date the structure, and also seal earlier foreshore deposits that may have been eroded away elsewhere. These dumps were normally capped by a hard, rammed stone working surface, often of chalk rubble or stone blocks. The gridiron surface may have been scoured out by later activities and may be exposed in section. If badly damaged, the stone surface can be entirely eroded away, leaving just the timber revetment.

usually

Gridirons, bargebeds and hards

Gridiron at Custom House showing timbers forming level structure on which the vessel would be grounded; chalk bargebed at Rotherhithe; section drawing of bargebed showing typical construction

thames discovery programmeforeshore factsheet number three

beach deposits sealing bargebed

Quay

Bargebed

Timber revetment

Surface of rammed chalk

Foreshore

Recording issues:

Is the structure level, or sloping?

Bargebeds are usually sited adjacent to the river wall for loading/unloading. How near is the structure to access points, to cranes or to quays?

Is there any evidence for ship breaking or repairing around the structure? e.g. ship timbers or nails?

What material is the structure made of? How was it constructed? How much care was taken in its construction? Has it been repaired or extended?

Is the structure shown on old maps? Can you use historic maps to date structures/activity?

Can the structure be related to an adjacent building or industry? Common examples include breweries, wharehouses or breaker's yards named on maps.

this factsheet has been generously funded by the Barbara Whatmore Trust

© thames discovery programme 2010

A 'hard' is a term sometimes used to describe a bargebed, although it may refer to a less specific area where the foreshore had been consolidated. The hard may be made from rammed stone, re-used architectural fragments, or even fragments of hulked vessels.

Slipways were used to launch boats which had been repaired, they can be confused with gridirons as they are often also made from parallel ships timbers, although they normally slope down the foreshore to allow the boat to be launched at lower tide.

Themes for researchAll the structures are designed to allow the vessel to settle in a stable position, this may indicate they were solely for flat bottomed vessels, however props may have been used to support keeled craft, especially on gridirons. Are the functions of the structures different, or are they different approaches to the same problem?

Some bargebeds were large and presumably expensive structures, especially when specifically built for an industry such as a brewery, whereas gridirons appear to be simpler, cheaper solutions to a similar problem. Detailed study of the structures, their date, and the associated foreshore and land structures and buildings will hopefully lead to a better understanding of the forms, development and function of the structures.

Local studiesAll these structures may be indicated on historic or Ordnance Survey maps which may also show additional structures such as wharehouses, shipyards, quays, wharves, jetties and cranes that may be related to the function of the structure. They may also be shown in illustrations of the river.

Further informationSearch for photos of gridirons, bargebeds, hards and slipways at the Thames Discovery Programme Flickr page: http://www.flickr.com/photos/thamesdiscovery/tags/