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Installation Guide for Recessed Covers in Paving.

1. If replacing an existing cover, ensure that there is sufficient depth to accommodate the new frame plus 20-40 mm of bedding mortar. If necessary, remove material from the top of the chamber to achieve this, taking care to avoid debris entering the chamber.

Installation guide for recessed covers - fig 1

2. Remove the cover from the frame using a set of heavy-duty lifting keys (Fig 2). For locked covers first remove the retaining bolts and set aside for later use. Refer to page 2 of the Wrekin Specification sheet for details of locking and lifting options and removal equipment.

Fig2

3. Position the frame over the manhole chamber, ensuring that the frame is large enough and can be positioned in such a way that no part of the frame overhangs the opening. Note that overhanging, unsupported framework can cause premature cover failure. (Fig. 3).

 Sections through frame

Figure 3 – Sections through frame.

4. Roughly mark out an area large enough to accept the frame. Clear away any loose or flaky material within this area to leave a sound surface for the new mortar bed. The level of the frame can be set with a straight edge from nearby finish if available (Fig 4). or by string lines set to finish level, temporarily shim the frame to judge the depth of the mortar bed.

Levelling the frame

Figure 4 – Levelling the frame

5. Lay down a mortar bed large enough to fully support the frame, leaving it proud enough for tamping.

6. Position the frame on the mortar bed in its previously established location and carefully insert the cover. If the cover is to be locked the previously removed bolts should now be inserted, do not fully tighten at this stage. Tamp down until the top of the cover and frame sits 2 to 3 mm below the finish floor line on all sides. (Fig. 5). Check that the cover sits in the frame without rocking and that the top of the cover and frame are level, making any necessary adjustments to achieve a good fit.

Tamping the cover & frame to finish level.

Figure 5 – Tamping the cover & frame to finish level.

7. Point the inside of the frame and remove any excess mortar. Haunch around the outside of the frame and over the fixing lugs, allowing enough free frame depth to accept the paving. (Fig. 6).

Frame bedded & haunched

Figure 6 – Frame bedded & haunched

8. Allow the mortar bed to cure before proceeding.

9. Insert plastic spacers between the cover and frame to ensure even gaps on all four sides and prevent distortion whilst paving. (Fig. 7).

Spacers between cover and frame

Figure 7 – Spacers between cover and frame.

10. Continue paving around the frame, cutting blocks as required to sit against the frame side, do not force blocks as this will distort the frame and make cover removal difficult. (Fig. 8).

Paving up to the frame

Figure 8 – Paving up to the frame.

11. Lay the paving in the cover on a 20 mm to 30 mm bed, (Fig 9) this can be sharp sand, or for areas more frequently accessed or subject to heavier loadings a screed / mortar bed is recommended. Gaps between the blocks must be fully filled with a proprietary grout to prevent movement. Note: Unbound permeable paving grit does not provide a stable bed or fill between blocks within a steel cover and should not be used.

Paving the cover

Figure 9 – Paving the cover.