Getting the core size wrong is a common and expensive mistake. Too small and the pipe won’t fit with its sleeve. Too big and you’ve removed more concrete than you need and left a large gap to fill. Use this reference guide to plan core sizes for plumbing, drainage and fire protection lines. Treat it as a starting point. Your MEP drawings and the sleeve or firestop system you’re using set the final size. How core size is chosen The core is never the same size as the pipe. You need space for: As a rule, the core is about 25 to 50mm larger than the pipe’s outside diameter. Check the firestop or sleeve manufacturer’s instructions for the exact annular gap allowed. Common core bit sizes Core bits come in standard sizes. These are widely used in the UAE: 52, 65, 82, 102, 112, 127, 152, 162, 200, 225, 250, 300, 350 and 400mm Larger diameters are available for risers and shafts. Plumbing (water supply) Pipe size Typical OD Typical core size 20 to 25mm PPR 20 to 25mm 52mm 32mm PPR 32mm 52 to 65mm 40 to 50mm PPR 40 to 50mm 65 to 82mm 63mm PPR 63mm 102mm 75 to 90mm PPR 75 to 90mm 112 to 127mm Insulated chilled water (add insulation thickness) Varies Size up one or two bits Drainage Pipe size Typical OD Typical core size 32 to 40mm (AC condensate, basin waste) 32 to 40mm 52 to 65mm 50mm 50mm 82mm 75 to 82mm 75 to 82mm 102 to 112mm 110mm (4″) soil pipe 110mm 152mm 160mm (6″) 160mm 200mm 200mm 200mm 250mm Floor drains and gully traps often need larger cores than the pipe alone, so check the fitting’s body size. Fire protection lines Nominal size Typical steel pipe OD Typical core size DN25 (1″) sprinkler branch 33mm 65mm DN50 (2″) 60mm 102mm DN65 (2.5″) 76mm 112 to 127mm DN80 (3″) 89mm 127mm DN100 (4″) 114mm 152 to 162mm DN150 (6″) 168mm 200 to 225mm DN200 (8″) 219mm 250 to 300mm Fire lines usually pass through fire-rated slabs and walls, so the gap around the pipe must be sealed with a tested firestop system. In Abu Dhabi, the Civil Defence Authority now requires contractors working on firestop and through-penetration systems to hold recognised firestop certification (ADCDA circular, June 2025). Check the firestop system’s required gap before you core. Size tips that save rework Book core cutting to the right size Scan and Core cores for plumbing, drainage and fire lines across Dubai and Abu Dhabi, with GPR concrete scanning before every hole. See our concrete cutting and coring services. Contact Scan and Core with your core schedule, or call +971 56 861 9006.