If you’re involved in flooring, construction, or renovation projects, you’ve likely come across the term screed. But unless you’re a seasoned pro, some of the lingo surrounding screeds can feel like a foreign language. Whether you’re a contractor, architect, DIYer, or just curious, this guide introduces the key terms you need to know to navigate the world of screeds with confidence.
Before we dive into the terminology, let’s clarify what a screed actually is. A screed is a layer of material that is applied to a subfloor to create a smooth, level surface for the final floor finish (like tile, carpet, vinyl, or wood).
Essential Screed Terms Explained
1. Bonded Screed
A bonded screed is laid directly onto a mechanically prepared concrete substrate using a bonding agent to ensure a strong adhesion. This method is ideal where thickness is limited.
Used when: You need a thin screed layer (typically 8–30mm) over a stable base.
2. Unbonded Screed
An unbonded screed is separated from the substrate by a membrane (such as polythene sheeting). This system allows the screed to move independently, reducing the risk of cracking due to shrinkage or substrate movement.
Used when: Moisture protection is needed or where there’s a risk of substrate movement (typically 15–50mm).
3. Floating Screed
Floating screeds are laid over insulation (e.g. thermal or acoustic), making them ideal for use with underfloor heating. The insulation layer “floats” the screed above the structural base.
Used when: Installing underfloor heating or needing insulation performance (typically 35–80mm).
4. Self-Levelling Compound
Also known as self-smoothing screed, this flowable compound spreads out evenly and finds its own level with minimal need for troweling. It’s ideal for thin layers and final finishes.
Used when: You need a perfectly flat finish before laying floor coverings (typically fever edge 0–10mm).
5. Traditional Sand and Cement Screed
This is the classic mix of sharp sand, cement, and water, typically mixed at a ratio of 1:3 to 1:4. It requires skilled application and manual compaction.
Used when: Durability is key and you don’t need fast drying (can be laid bonded, unbonded or as a floating application).
6. Liquid Screed (Flowing Screed)
Usually based on anhydrite (calcium sulphate) or cement, liquid screeds are pumped into place and levelled using a dapple bar. They offer fast installation and are ideal for large areas.
Used when: Speed, thinness and level precision are top priorities (can be laid bonded, unbonded or as a floating application).
7. Drying Time
This is the period required for the screed to dry enough to accept flooring. Drying time varies by type and thickness but is critical to avoid future floor failures.
Rule of thumb: 1mm per day for traditional screeds up to 40mm; faster with liquid screeds.
8. Curing
Curing is the process of maintaining moisture and temperature to allow proper strength development. Poor curing can lead to cracking, shrinkage, or weak screeds.
Best practice: Cover with plastic sheeting or use curing agents immediately after laying.
9. Foot Traffic
The time required after laying the screed before you can walk on the screed without making footprint indents.
10. Environment
The conditions that the screed is sat in, e.g. temperature and humidity are important in the curing process, along with air flow.
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Understanding screed terminology isn’t just for the experts – it’s essential for anyone involved in floor construction or renovation. By learning these key terms, you’ll not only communicate better with contractors but also make smarter, faster, and more cost-effective decisions.
