Curved Mosaic Column Border and Niche Mitres
A hotel lobby has a circular column of 600 mm radius to be wrapped with a 300 mm high mosaic border. The mosaic comes in 300 × 300 mm sheets of 20 × 20 mm glass chips with 2 mm joints. Adjacent to the column, a shower niche in 600 × 300 mm porcelain requires external corners. The available tools are a manual tile cutter, a 4-inch angle grinder with a continuous diamond blade, diamond polishing pads, a 35 mm diamond hole saw, and a wet sponge. The first mosaic sheet has chipped edges, the curve is faceted with 3 mm gaps between sheet edges, and two niche corners show 1.5 mm open joints.
1. Select the cutting and shaping methods for the curved mosaic and porcelain niche, and explain why each is suitable.
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For the curved column, do not try to bend rigid mosaic sheets dry. Use the wet saw or angle grinder with a continuous diamond blade to cut the 300 × 300 sheets into narrower strips, or separate chips at the joints. For a 600 mm radius, cut the backing mesh between chips at the curve and fan the chips slightly; the 2 mm joints allow a fair curve. Use a flexible adhesive (C2TE S1) and a 4–6 mm notched trowel; press the mosaic with a grout float or rubber roller so the chips sit level. For the niche, use the manual cutter for straight cuts on 600 × 300 porcelain and the angle grinder with a diamond pad for the external mitre. Polish with 200–400 grit pads. For pipe holes, use the 35 mm diamond hole saw with water, not a hammer drill.
2. Set out the sequence for installing the mosaic border and the niche corners.
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Sequence: 1) set out the border height of 300 mm with a laser, including the 2 mm joints; 2) dry-fit sheets around the column, numbering them; 3) cut sheets into strips and separate the mesh at the curve; 4) apply adhesive in small sections because glass mosaic can slump; 5) bed with a float and check with a straightedge around the curve; 6) clean joints before adhesive sets; 7) grout with a fine-joint grout. To avoid chipping glass mosaic, use a sharp continuous blade, low feed pressure, and water; do not use a tile nibbler on glass. Support the sheet with a stiff board when cutting. For the niche, cut and polish the mitres before fixing, and dry-assemble the corner to check the 1.5 mm gap.
3. Inspect the defects shown and state the corrective action for the chipped mosaic and open niche joints.
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Inspect the first sheet: chips on the edge mean the blade is dull, the feed is too fast, or the glass is unsupported. Replace or dress the blade, reduce pressure, and use water. Faceting with 3 mm gaps means the sheets were forced around the curve instead of being cut and fanned; remove the affected sheet before the adhesive cures, clean the back, and re-fix with the mesh cut between chips. For the niche corners, a 1.5 mm open joint is too wide for a 2 mm joint design and will collect water. Rake out loose material, check the mitre angle, and re-cut or fill with a matching epoxy or grout only if the substrate is sound. Best practice is to re-cut the mitre so the joint closes to 1–2 mm. Record photos and re-inspect after grouting.