Patio Paving Calculator

Paving calculations divide the total area by the area of a single slab or paver block. Common UK slab sizes include 450 × 450 mm, which gives approximately 5 per m², 600 × 600 mm at approximately 2.8 per m², and 600 × 300 mm at approximately 5.6 per m². Block paving at 200 × 100 mm works out at roughly 50 blocks per m². The pattern you choose then changes the waste allowance, since a straight bond loses about 5%, a running bond 7%, and herringbone or random natural stone 10 to 15%.

Allow a 10 mm joint between slabs, which reduces coverage slightly, and add 5 to 10% extra for cuts and breakage. A 20 m² patio in 600 × 600 mm slabs, each covering 0.36 m², needs 56 slabs before waste and 62 once the allowance goes on. The calculator also estimates sub-base material. A compacted Type 1 sub-base of 100 to 150 mm is standard for patios, while driveways need 150 to 200 mm, with a mortar or sand bed of 25 to 40 mm sitting on top.

Enter the area dimensions, slab size and joint width and you get the slab count, the sand or mortar quantity, the sub-base in tonnes and an estimated cost. One planning point is worth settling before you order anything, because a driveway with more than 5 m² of impermeable paving may need planning permission unless you use a permeable surface or drain the run-off to a lawn or border.

Prices in 2026 span a wide field. Basic concrete slabs cost £8 to £20 per m² and riven or textured concrete £20 to £40. Clay or concrete block paving is £20 to £50 per m² plus sand bedding. Natural Indian sandstone and York stone run £30 to £80, limestone £40 to £90, slate flags £50 to £120, and granite setts or cobbles £40 to £150. Porcelain in 20mm outdoor thickness is £40 to £100 and neither fades nor needs sealing. Fitting labour adds £40 to £80 per m² depending on the pattern, so a typical UK patio lands at £80 to £180 per m² installed.

The sub-base is what makes paving permanent. Strip the topsoil to 200 to 300mm, lay a weed membrane, then compact 150mm of MOT Type 1 at £40 to £60 per tonne, which is roughly 2 tonnes for every 10 m² at that depth. A wacker plate hires for about £50 a day. Slabs then bed on 25 to 40mm of sharp sand or mortar, while block paving uses a 50mm sand bed with jointing sand swept in after laying. Set a fall of 1:60 away from the house, a gradient of 1.67%, and add drainage channels such as Aco Drain at building edges and across large patios.

Planning permission depends on where the paving goes. In England, front gardens have been treated differently since 2008: permeable surfaces such as gravel, permeable block paving and porous concrete count as permitted development, while impermeable surfaces including sealed concrete and traditional block paving on an impermeable sub-base need permission. Back gardens are generally fine without permission below 50% coverage of the curtilage. Listed buildings may need listed building consent for any external work to the curtilage, conservation areas apply tighter rules, and an Article 4 direction removes permitted development rights in some streets, so ask the council first.

Longevity varies by material and so does the upkeep. Concrete paving lasts 25 to 50 years but weeds colonise the joints, which is why polymeric jointing sand or an annual treatment pays off. Sandstone lasts 40 to 70 years and grows algae in damp shade, so pressure wash it once or twice a year. Porcelain lasts 50 years or more, resists stains and needs no sealing. Block paving lasts 25 to 40 years and usually wants relevelling every 5 to 10 years where the ground settles. A pressure washer costs £100 to £300, sealant for porous stone is £20 to £40 a litre covering 4 to 8 m² and wants redoing every 2 to 5 years, and polymeric jointing sand lasts 7 to 15 years.