Screeding has its own vocabulary, and a quote, a data sheet or a flooring fitter's checklist can be hard to follow without it. This glossary explains the terms we use most, in a sentence or three each, with the source for every figure. Where we have a fuller page on a term, or a service that covers it, the entry links to it.
Six of the most searched terms have their own pages: feather edge, power floating, screed rails, screed board, laitance and cementitious screed.
B
Bonded screed
A screed laid onto a mechanically prepared base so that it bonds to it. The MPA gives a minimum thickness of 25mm, with 40mm normally specified to take up deviations in the base. See our bonded screed service.
Source: Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023.
C
Calcium sulphate (anhydrite) screed
A screed with a calcium sulphate binder in place of cement, usually pumped as a liquid. It must not be reinforced with steel, is generally unsuitable for damp areas, and forms a surface laitance that must be removed before tiling. See our anhydrite flow screed service and our anhydrite screed guide.
Sources: Floor screeds, The Concrete Centre; The Tiling Guide, The Tile Association.
Cementitious screed
Cementitious screed is any floor screed whose binder is cement, from traditional semi dry sand and cement to modern cement based liquid screeds. The term is mostly used to tell these apart from calcium sulphate, or anhydrite, screeds, which set and behave differently. Read the full entry on cementitious screed.
CM test (carbide method)
A moisture test that gives the moisture content of a screed sample as a percentage by weight, to BS EN 13892-10. Gyvlon recommends it, or oven drying, for calcium sulphate screeds, and gives 0.5% as roughly equal to 75% RH. Our guide on how long screed takes to dry covers moisture testing.
Source: Post installation guidance, Gyvlon (Anhydritec), 2024.
Curling
An upward deformation of the edges of a screed caused by differential shrinkage. Unbonded and floating cement sand screeds are most at risk; calcium sulphate screeds shrink less and are not prone to it. We put curled screeds right as part of our screed repairs.
Sources: Floor screeds, The Concrete Centre; Screed, Designing Buildings Wiki.
D
DPM (damp proof membrane)
A membrane that keeps ground moisture away from the screed. A screed laid over a membrane is unbonded by definition, and Cemfloor lays its unbonded screed on 1000 or 500 gauge polythene. We lay membranes as part of our insulation and membranes service; liquid options are in our liquid DPM guide.
Sources: Floor screeds, The Concrete Centre; Installation of Cemfloor screed, Cemfloor.
E
Edge strip
A compressible strip fixed around walls, columns and upstands before a screed is laid, to accommodate the natural movement of the floor. Cemfloor calls for a strip at least 5mm thick, and CEMEX a 5mm closed cell foam strip. Part of our insulation and membranes work.
Sources: Installation of Cemfloor screed, Cemfloor; Supaflo Rapide datasheet, CEMEX UK.
F
Feather edge
In floor work, feather edge means either a long aluminium straightedge with one tapered edge, or a patching and smoothing compound that can be spread down to nothing at its edges. Both are products you buy, not services, so this page explains them from a screeding contractor's point of view. Read the full entry on feather edge.
Floating screed
A screed laid on thermal or acoustic insulation and separated from walls and pipes. The MPA gives 75mm as the minimum for cement sand, with 65mm normally accepted in housing; calcium sulphate floating screeds go down to about 35mm in homes and 40mm commercially. See insulation and membranes.
Sources: Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023; Screed, Designing Buildings Wiki.
Flow screed
The trade name for a pumped liquid screed that levels itself, most often calcium sulphate based and delivered ready mixed. Cement based flowing screeds also exist. See our liquid screed and anhydrite flow screed services and our anhydrite screed guide.
Sources: What's the difference between sand and cement and self levelling screeds?, Flowcrete UK; Installation of Cemfloor screed, Cemfloor.
G
Granolithic screed
A hard wearing topping of cement and a hard fine aggregate such as granite, generally mixed at about 2.5 parts aggregate to 1 part cement by volume and used where the floor itself is the wearing surface, such as factory floors. Concrete wearing surfaces are covered by BS 8204-2. For a strong commercial screed, see high strength screed.
Sources: Granolithic, Wikipedia; Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023.
H
Hollow screed
Screed that sounds hollow or drummy when tapped, because it has lost its bond or was never fully compacted. The MPA notes that hollowness, like curling, is most likely at the joints, cracks and perimeters of unbonded screeds. See our screed repairs.
Source: Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023.
L
Laitance
Laitance is the weak, powdery skin that forms on the surface of new concrete and many screeds, and especially on calcium sulphate liquid screeds. It has to come off before tiles, adhesives or levelling compounds go down, because anything bonded to it is only as strong as the laitance itself. Read the full entry on laitance.
Latex screed
The flooring trade's name for a thin latex based levelling and smoothing compound, used to smooth old tiles, overboarded timber and uneven concrete before vinyl, LVT or carpet. ARDEX says its ARDITEX latex range covers virtually any substrate without the need to prime. See our latex screed service.
Source: Latex based levelling and smoothing compounds, ARDEX UK.
M
Movement joint
A planned joint, also called an expansion or control joint, that lets a screed move with shrinkage and temperature change. Cemfloor allows bays of up to 150m² unheated and 100m² heated without control joints, with joints at doorways, where a floor is more than four times as long as it is wide, between heating zones and every 15m in corridors. Gyvlon says never to tile over joints in a screed.
Sources: Installation of Cemfloor screed, Cemfloor; Post installation guidance, Gyvlon (Anhydritec), 2024.
P
Power floating
Power floating is the machine finishing of fresh concrete or sand and cement screed. It is done once the surface can take the weight of the machine, and it gives a flat, dense floor that is ready for the floor covering or, on some slabs, left as the finished surface. Read the full entry on power floating.
R
Relative humidity (hygrometer) test
A test of the relative humidity (RH) given off by a screed, read with a hygrometer. Screeds are generally regarded as dry at 75% RH or below. Gyvlon notes that BS 8204-7 says RH testers are not accurate on calcium sulphate screeds above 85% RH, where a CM test or oven drying is used. See how long screed takes to dry.
Sources: What's the difference between sand and cement and self levelling screeds?, Flowcrete UK; Post installation guidance, Gyvlon (Anhydritec), 2024.
S
Screed board
Screed board is used for two different things: the flat board or aluminium rule drawn across wet screed or concrete to level it, and a factory made dry screed panel laid in place of a wet screed. Both are products, and this page explains each from a screeding contractor's point of view. Read the full entry on screed board.
Screed fibres
Short fibres, normally polypropylene, mixed through a screed to help control cracking. CEMEX describes fibres as a substitute for light mesh that is always in the right position. See our fibre reinforced screed service.
Sources: Floor screeds, The Concrete Centre; Readyscreed technical datasheet, CEMEX UK.
Screed mesh
Light reinforcement, either fine steel or glass mesh, laid within a screed. For its unbonded and floating K-Screed, Flowcrete specifies either steel fabric to BS 4483 reference D49 throughout or polypropylene fibres with a strip of D49 fabric across day joints. Calcium sulphate screeds must not be steel reinforced. Mesh and fibres are compared on our fibre reinforced screed page.
Sources: Floor screeds, The Concrete Centre; Isocrete K-Screed technical data, Flowcrete.
Screed primer
A coat applied to a dry screed before adhesive or levelling compound, to control suction and help the bond. Gyvlon recommends most acrylic or epoxy primers on its calcium sulphate screeds, following the maker's guidance on dilution and number of coats. Preparing the surface first is part of our floor preparation service.
Source: Post installation guidance, Gyvlon (Anhydritec), 2024.
Screed rails
Screed rails are level guides set at the finished height of a floor so that a straightedge or screed board can be drawn along them to strike the material off flat. They are a tool you buy or hire, and this page explains them from the point of view of a screeding contractor. Read the full entry on screed rails.
Screed sealer
A primer or sealing coat used to close the surface of a screed. The Tile Association advises sealing a calcium sulphate screed with an appropriate primer repeatedly until no more is absorbed, and letting it dry before tiling. For a floor that stays bare, see our guide to sealing a concrete floor.
Source: The Tiling Guide, The Tile Association.
Self levelling screed
A pumpable screed that flows to the required level and surface regularity on its own; BS 8204 calls it pumpable self smoothing. A 5 to 10mm cementitious self levelling smoothing screed can be dry enough for vinyl after 24 hours. See our self levelling screed service.
Sources: Floor screeds, The Concrete Centre; What's the difference between sand and cement and self levelling screeds?, Flowcrete UK.
Semi dry screed
A sand and cement screed mixed with just enough water to be compacted, typically 65 to 75mm thick when unbonded or floating (bonded semi dry screeds can be 25 to 40mm) and laid by hand at around 125 to 150m² a day. It must be fully compacted to remove air voids. See our sand and cement screed service.
Source: What's the difference between sand and cement and self levelling screeds?, Flowcrete UK.
Surface regularity (SR1, SR2, SR3)
BS 8204 grades the flatness of a floor into surface regularity classes, SR1 being the flattest, checked by laying a 2m straightedge on the floor under its own weight and measuring the gaps beneath it with a slip gauge or graduated wedge. CEMEX says SR2 or better is routinely achieved with its flowing screed. Where a floor finish needs a flatter surface, see floor levelling.
Sources: Surface flatness technical guidance note (BS 8204-2 method), SMD; Supaflo Rapide datasheet, CEMEX UK.
U
UFH screed depth
The depth of screed needed over underfloor heating pipes. Cemfloor specifies at least 25mm above the pipes for its cement based liquid screed, and The Concrete Centre gives 30mm minimum cover for pumpable screeds, so always follow the screed maker's sheet. See our underfloor heating screed service.
Sources: Installation of Cemfloor screed, Cemfloor; Floor screeds, The Concrete Centre.
Unbonded screed
A screed laid on a separating layer, such as a membrane, or on a base not prepared for bonding. The MPA gives 50mm as the minimum for cement sand, with 70mm specified to allow for deviations in the base; unbonded calcium sulphate screeds go down to 30mm. Our screed thickness guide compares depths.
Sources: Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023; Floor screeds, The Concrete Centre.
Sources
- Mortar data sheet 22: Screeds, Mineral Products Association, issue 3, October 2023, accessed 25 October 2026
- Floor screeds, The Concrete Centre, accessed 25 October 2026
- The Tiling Guide, The Tile Association, accessed 25 October 2026
- Post installation guidance, Gyvlon (Anhydritec), 2024, accessed 25 October 2026
- Screed, Designing Buildings Wiki, accessed 25 October 2026
- Installation of Cemfloor screed, Cemfloor, accessed 25 October 2026
- Supaflo Rapide datasheet, CEMEX UK, accessed 25 October 2026
- What's the difference between sand and cement and self levelling screeds?, Flowcrete UK, accessed 25 October 2026
- Granolithic, Wikipedia, accessed 25 October 2026
- Latex based levelling and smoothing compounds, ARDEX UK, accessed 25 October 2026
- Readyscreed technical datasheet, CEMEX UK, accessed 25 October 2026
- Isocrete K-Screed technical data, Flowcrete, accessed 25 October 2026
- Surface flatness technical guidance note (BS 8204-2 method), SMD, accessed 25 October 2026
Each term page lists its own sources.
