1. Scope
- Class L covers all ancillary works required during pipe-laying and pipe excavation, including:
- Pipe supports (when not included in Class K structural supports).
- Pipe protection (encasement, wrapping, coating, sleeving, corrosion protection).
- Bedding, surround, haunching, and backfilling of pipes.
- Temporary works for excavation (shoring, timbering, trench boxes).
- Dewatering and maintaining dry conditions in pipe trenches.
- Extraordinary ancillaries such as crossings (roads, railways, rivers).
👉 In simple terms:
- Class I = Pipes
- Class J = Fittings & Valves
- Class K = Manholes & chambers
- Class L = The “everything around the pipe trench” – bedding, protection, supports, shoring, dewatering, etc.
2. General Principles
- Unit of measurement:
- Bedding, surround, haunching → m (measured along the length of pipeline).
- Wrapping / Coating / Sleeving → m or m², depending on specification.
- Concrete encasement → m³.
- Shoring / timbering → m² of surface supported.
- Dewatering → sum (lump sum) or litres / m³ if specified in contract.
- Rates include:
- Labour, materials, placing, removal (for temporary works).
- Protection of adjoining services.
- Maintaining stability of excavation until permanent works are in place.
3. Sub-classifications
L1 – Bedding and Surround to Pipes
- Material placed below, around, and above pipes to ensure stability and prevent damage.
- Types:
- Sand / granular bedding.
- Haunching (side support).
- Surround (encasing with sand, gravel, concrete).
- Measurement: per metre (m) of pipe length, classified by pipe size and type of bedding/surround.
L2 – Encasement, Wrapping, Coating, Sleeving
- Concrete encasement → for high load conditions (under roads, railways).
- Protective wrapping/coating → bituminous, epoxy, polyethylene, coal tar.
- Sleeving → placing pipe inside casing pipe (usually steel or HDPE).
- Cathodic protection may also be listed under this section.
Measurement:
- Encasement → m³ of concrete.
- Wrapping/coating → m (length of pipe protected).
- Sleeving → m (length of carrier pipe in casing).
L3 – Shoring, Timbering, and Trench Supports
- Temporary supports to keep trench walls stable during excavation/pipe-laying.
- Types:
- Timbering, steel sheeting, trench boxes, hydraulic shoring.
- Measurement: per m² of vertical face supported, classified by depth.
- Removal after backfilling included in rate.
L4 – Dewatering and Ancillaries
- Includes pumping, well points, or other methods to maintain dry working conditions.
- Can also include trench sumps and drainage channels.
- Measurement:
- Normally lump sum (sum) for whole pipeline section.
- Sometimes per cubic metre of water removed (if specified).
L5 – Special Crossings and Protection Works
- Road, railway, canal, or river crossings requiring extra protection.
- Concrete slabs, casing pipes, culverts, or duct crossings.
- Measurement: per metre (m) length of pipe crossing or per number (No.) if specified.
4. Measurement Rules
- Pipe bedding & surround → measured separately from excavation (Class E).
- Encasement → measured by volume (m³), classified by concrete grade.
- Shoring/timbering → measured by area (m²) of trench face supported.
- Dewatering → measured by lump sum (sum) unless specified otherwise.
- Crossings → measured separately with detailed description.
5. Examples of BOQ Items (Class L)
- Sand bedding and haunching for 200 mm dia DI pipe, thickness 150 mm below and 300 mm above crown – m.
- Granular bedding for 400 mm dia RCC NP3 pipe, thickness 100 mm, with side haunching – m.
- Concrete encasement, M20 grade, for 300 mm dia DI pipe, 100 mm all around – m³.
- Bituminous wrapping to 150 mm dia MS pipe, two coats, incl. surface preparation – m.
- PE sleeve (250 mm dia HDPE casing) for 150 mm dia DI pipe crossing road – m.
- Timbering to trench sides, depth exceeding 3.0 m but not exceeding 4.5 m, incl. fixing and removal – m².
- Steel trench box support for trench depth 2.0–3.0 m – m².
- Dewatering by pumping, complete for pipeline section between chainage 0.0–200.0 m – Sum.
- Concrete slab protection to 200 mm dia pipe crossing under road, 150 mm thick RCC M25 – m².
✅ In summary:
- Class L is all about support, protection, and temporary works around pipelines.
- It ensures safety of workers, durability of pipes, and protection under special conditions.
- Measurements are mixed (m, m², m³, No., or Sum) depending on the work type
