Substrates & preparation

New Concrete Slabs

A freshly cast slab needs the right cure, a laitance-free surface for bonded work, and clean falls before liquid screed follows the groundworker.

Power-Floated Slabs

A power-floated surface is dense and low-porosity, so mechanical opening followed by a compatible primer is what makes bonded adhesion realistic.

Beam and Block

Beam and block floors need jointing and deflection assessed as structural items, with insulation and sand blinding handling the practical prep for screed.

Hollowcore Planks

Hollowcore floors need camber surveyed, joints grouted, and an acoustic separating layer confirmed before liquid screed brings the floor to a level finish.

Suspended Timber Joists

Screeding over suspended timber joists depends entirely on the rigidity of the deck above them — deflection is the limiting factor, not the joists alone.

Chipboard Decking

P5 moisture-resistant chipboard is a common deck under liquid screed on timber floors, but it needs the right grade, fixings and taped joints.

Plywood Decking

Structural plywood offers more consistent stiffness than chipboard as a deck under liquid screed, useful where spans or loading are more demanding.

PIR Insulation Boards

PIR insulation gives strong thermal performance per millimetre under liquid screed, but its foil facings and joints need careful taping to control grout loss.

EPS Insulation Boards

EPS is a cost-effective, widely used insulation under liquid screed, provided the correct load grade is chosen and joints are properly sealed.

XPS Insulation

XPS insulation offers higher compressive strength and lower moisture absorption than standard EPS, useful in specific loading or damp-prone situations.

Phenolic Insulation

Phenolic foam boards offer some of the lowest U-values per millimetre of any rigid insulation, useful in the most depth-constrained floor build-ups.

Sand Blinding

A thin sand blinding layer smooths out an irregular hardcore or block surface so insulation boards sit flat and undamaged beneath a liquid screed.

Old Tile & Adhesive Residue

Tile adhesive and grout residue left on a substrate is a poor base for a bonded screed, so full mechanical removal or a floating build-up is usually needed.

Overlaying Old Screed

An existing screed can sometimes stay in place as a base for a new liquid screed, but its condition and how it interacts with the new pour needs assessing first.

Asphalt Substrates

Mastic asphalt floors, once common as a damp-proof and level base, are usually treated as a stable substrate to float over rather than bond to.

Contaminated Substrates

Oil, fuel or chemical contamination in a concrete substrate needs identifying and treating before insulation or a bonded screed goes down, or it will compromise the pour.

Damp Substrates

Persistent damp in a substrate needs diagnosing and controlling at source before insulation and screed are installed, rather than relying on the new floor build-up to mask it.

Basement Tanking

Screeding a basement floor means working carefully around the waterproofing system already in place, since damage to tanking can be very costly to fix later.

Radon Membranes

In radon-affected areas of the South West, the gas membrane's continuity and sealed penetrations matter more than usual before liquid screed is poured over it.

Ground Gas Membranes

Sites with methane or other ground gas risk need a gas-resistant membrane detailed to a specific gas protection scheme before insulation and screed go down.

DPM Lapping & Junctions

A damp-proof membrane only works if its laps, upstands and junctions with walls and other membranes are continuous — gaps undermine the whole system.

Edge Insulation & Perimeters

A compressible edge strip around the perimeter of a liquid screed floor allows for thermal movement and helps isolate the screed acoustically from the walls.

Taping & Sealing Joints

Grout loss through unsealed joints is one of the most common causes of an uneven or thin patch in a finished liquid screed floor, and it's entirely preventable.

Overlaying Old Quarry Tiles

Old quarry tiles are dense, low-absorption and often uneven, so they're usually treated as a base for a floating build-up rather than something a screed bonds to directly.

Painted & Sealed Slab Preparation

Paint, sealant and curing compounds on a concrete slab break the bond a liquid screed depends on, so they generally need mechanical removal or a floating design used instead.

Underfloor Voids & Service Ducts

Ducts, voids and access chambers within a floor need their covers, upstands and edges fixed and sealed before screeding, or the pour will find its way in.

Stepped & Split-Level Slabs

Level changes between rooms or slab areas need dams, edge details and a clear pour sequence, since a self-levelling screed will naturally seek the lowest point.

Taping & Sealing Insulation Layers

Gaps between insulation boards let liquid screed migrate into the void beneath, so joints are taped or sealed as a routine step before the pour.

Drains, Penetrations & Thresholds

Drains, pipework and thresholds each interrupt a floor's finished level, so their protection and detailing has to be planned before the screed goes down.

Mezzanines & Raised Access Floors

Mezzanine and raised access floors are lightweight, deflecting structures, so deck deflection and point loading need checking before a liquid screed is specified.

Cellular Glass Insulation Preparation

Cellular glass insulation is rigid, moisture-resistant and load-bearing, but its brittle nature and joint pattern need particular care before a floating screed is poured.

Site Readiness Checklist

A liquid screed pour depends on a run of site conditions all lining up at once, so a short readiness check before the date is confirmed avoids costly delays.

Weatherproofing the Envelope

Liquid screed needs a reasonably weathertight building envelope before it's poured, since wind, rain and temperature swings all affect a wet, self-levelling material.

Temperature & Ventilation Control

Liquid screed cures best in stable, moderate temperatures with controlled ventilation, rather than being forced dry with excessive heat or draughts.

Protecting Adjoining Finishes

Where a liquid screed pour sits next to finished or sensitive areas, protection measures reduce the risk of splashes, dust and accidental damage during the works.

Access & Hose Routes

Constrained sites — terraced houses, narrow plots, upper floors and restricted parking — need pump access and hose routing worked out before the pour date, not on the day.

Waste & Washout Management

A liquid screed pour generates washout water and some material waste that needs a sensible, pre-agreed disposal point rather than being dealt with on the fly.

Surveying & Level Datums

A quick survey of the existing substrate and an agreed level datum let a liquid screed pour achieve a flat, level finish even where the base below varies.

Moisture Risk Assessment

An existing floor being overlaid or replaced needs a moisture risk assessment, since ground moisture, past leaks or a missing DPM behave differently to a new slab.