Plastering & Rendering Calculators

Plastering remains one of the most essential finishing trades in UK construction, covering everything from internal skim coats on new plasterboard to full external rendering on blockwork walls. Whether you are a professional plasterer pricing a job or a DIY homeowner tackling a single room, getting your material quantities right from the start saves time, money, and unnecessary trips to the builder's merchant.

In the UK, the most commonly used plaster products come from British Gypsum, with their Thistle range dominating the market. Thistle Multi-Finish is the go-to skim coat plaster for most internal work, while Thistle Bonding Coat and Browning are used as undercoats on different substrates. For boarding, standard plasterboard sheets in the UK measure 2400mm × 1200mm, with 12.5mm thickness being standard for walls and 9.5mm for ceilings. Our plasterboard calculator helps you work out exactly how many sheets you need, including a wastage allowance for cuts.

External rendering in the UK follows well-established practices using sand and cement mixes, typically applied in two coats (scratch coat and top coat). Modern alternatives include monocouche (one-coat) renders from manufacturers like K Rend, Weber, and Parex, which offer coloured finishes and improved weather resistance. Our rendering calculator covers traditional sand and cement mixes with accurate ratios for different application thicknesses.

UK Building Regulations do not specifically regulate plastering work, but the finished surface must meet fire resistance requirements under Approved Document B. Plasterboard provides inherent fire resistance (typically 30 minutes for 12.5mm board), which is why it is used so extensively in UK domestic construction. For rooms requiring enhanced fire protection, such as garages attached to dwellings, fire-rated plasterboard (pink board) is required. The plaster coverage calculator ensures you order the right number of bags for any job, whether it is a small patch repair or a full house re-plaster.

Dot and dab (adhesive fixing) has become the preferred method for fixing plasterboard to masonry walls in new-build UK housing, replacing traditional wet plastering in many applications. This method uses plasterboard adhesive (such as British Gypsum Gyproc Dri-Wall Adhesive) applied in dabs to the wall before pressing the board into position. For period properties and renovation work, traditional wet plastering with undercoat and skim remains the standard approach, particularly where walls are uneven or where a solid, robust finish is required.