What Depth Should Screed Be? A Complete UK Guide

Getting the screed depth right is one of the most important decisions on any flooring project. Too thin and the screed will crack or fail. Too thick and you waste material and extend drying time unnecessarily. This guide covers the correct depth for every screed type and application, in line with BS 8204.

Minimum Depths for Liquid Screed

Liquid screed — including anhydrite and gyvlon — can be laid thinner than traditional sand and cement due to its self-levelling nature and higher compressive strength. The BS 8204 minimums are: 25mm over underfloor heating pipes (bonded or floating) and 30–35mm for floating applications without UFH. Always confirm the pipe height with your UFH installer before agreeing screed depth.

Minimum Depths for Sand and Cement Screed

Traditional screed requires greater depth to achieve sufficient structural strength. BS 8204 specifies 25–40mm for bonded applications, 50mm minimum for unbonded screeds laid on a DPM or separating layer, and 65–75mm for floating screed laid over insulation. These minimums exist because thinner traditional screed lacks the mass needed to resist curling and cracking.

Depth and Drying Time

Depth directly affects drying time. Liquid screed dries at approximately 1mm per day up to 40mm, then slows beyond that. Sand and cement screed dries at roughly 1mm per day throughout. A 75mm traditional floating screed will need around 75 days before floor finishes can be laid under normal UK conditions. Factor this into your programme when specifying depth.

BS 8204 Compliance

BS 8204 governs screed specification and installation across the UK. It sets minimum depths, mix ratios, substrate preparation requirements, and testing procedures. For commercial projects, compliance is typically a contractual requirement. screeding.com provides a BS 8204 compliance certificate on completion of every project. If you are unsure of the correct depth for your project, contact us for free advice before you book.