Measure the installed frame before ordering a replacement cover. Keep the old panel dimensions as a separate record. They describe the component being removed, but they do not show every feature of the opening that the replacement must fit.
A trench cover grating survey should identify the cover, its frame and the surrounding route. Use a location mark on the drawing and in every photograph so measurements from neighbouring openings cannot be mixed.
Record the opening and the seat separately
Show the clear opening beneath the cover and the space available for the cover itself. Draw a section through each different frame edge, including the bearing ledge, recess depth and finished surface level. Label the dimension reference points; a number without its measuring points is hard for a fabricator to use.
Measure along the opening at several marked positions and check the diagonals where access allows. Note changes in width, damaged edges and any visible distortion. Provide the measurements as recorded. Let the responsible reviewer decide the fabrication size and required clearance from the actual frame information.
Photograph corners, joints and the underside where it can be inspected safely. Identify loose, corroded or damaged frame areas for review before placing the replacement order. A new panel leaves an unresolved frame defect in the assembly unless that defect is addressed.
Include everything that affects removal
Show pipe penetrations, projecting bolts, adjacent kerbs and any equipment over the cover. Record the space available to lift and move a panel. Ask the maintenance team whether the channel must open fully or whether separate sections suit the cleaning task.
For segmented covers, mark each section and its supports. Ask the supplier for the finished weights and proposed lifting arrangement so the contractor can review handling. Include clips, locking devices or other retention details in the survey rather than treating them as accessories to choose after delivery.
Describe the route above the cover
State who or what crosses the opening and how the route is used. Identify pedestrian access, trolleys or vehicles in the brief for the designer. Keep the support and fastening information with that brief so the review covers the assembled cover and frame.
If the existing product is a sealed manhole cover, establish whether sealing or another function must remain. An open grating proposal needs a review of those requirements. A similar outside dimension or a general duty description does not document product equivalence.
The approval drawing should reference the site measurements, cover marks, agreed panel sizes and any frame repairs. At delivery, check those marks before installation. Keep the accepted drawing with the maintenance record, including any final site changes, so the next replacement can be ordered from a traceable description of the installed assembly.
