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Stay bracing and vertical sheeting

Short answer

Stay bracing uses spaced vertical poling boards with horizontal struts for firm soil up to 2 m depth. Vertical sheeting uses continuous vertical boards touching each other, held by walings and struts, for loose soil up to 3 m or more. Sheeting provides full-face support unlike the gaps in stay bracing.

Describe stay bracing and vertical sheeting.

Both are methods of timbering trenches to hold the sides of the excavation.

Stay bracing

Used in fairly firm soil for depths up to about 2 m. Vertical boards (poling boards, 200 x 40 mm) are placed at 2-3 m centres on opposite faces of the trench and kept apart by horizontal struts (props). The poling boards are placed at intervals, leaving the soil between exposed. The struts are fixed at 1.2-1.5 m centres vertically, and can be wedged.

   |board   strut   board|
   |  |==========|  |
   |  |          |  |
   |  |==========|  |   (soil between boards
   |__|__________|__|    left unsupported)

Vertical sheeting

Used in loose soil and for depths up to 3 m (or more). Vertical boards (sheeting), 25-40 mm thick, are placed side by side touching each other, so the whole face is covered. They are held by horizontal walings (120 x 120 mm) on the inside, with struts across the trench at about 1.2-1.5 m c/c.

   |sheet|waling|  strut  |waling|sheet|
   ||||||=====o===========o=====||||||
   ||||||                      ||||||
   ||||||=====o===========o=====||||||

Difference: stay bracing leaves gaps between boards, while vertical sheeting gives continuous support. Sheeting is thus used for looser soil.

✓ Answer checked by Claude Opus 5.5 (high effort)

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