Preparing Your Floor for Liquid Screed: A Somerset Checklist

You have a date for the screed, or you are about to ask for one. The pour itself is quick. What takes the time, and what decides whether the day goes well, is the preparation that happens before the pump arrives. This checklist is written for homeowners managing their own project and for builders who want the floor ready first time, on sites across Somerset and Dorset.

Why preparation matters so much with liquid screed

Traditional screed is a semi-dry sand and cement mix that stays where it is put. Liquid screed is pumped through a hose as a fluid and flows to its own level. That is what gives it a flat, consistent finish, but it also means it will run into any gap, hole or open joint it can reach.

So the floor has to be turned into a sealed tray before the pour.

Who gets the floor ready

Preparation is normally done by the builder and, where there is underfloor heating, the heating installer. Somerset Screed Company supply and install the liquid screed. We do not install insulation, membranes or underfloor heating, so agree early who on your project is responsible for each item on this list.

A weathertight building

The building should be weathertight before the screed goes in. That means the roof is on and window and door openings are glazed or securely covered.

Fresh liquid screed needs protecting from rain, frost, strong draughts and direct sunlight while it sets. Once it has set, ventilation becomes important for drying, and your installer will tell you when to open the building up.

A clean, sound base

Sweep the base thoroughly and clear away rubble, offcuts, fixings and anything sharp. Debris left under the insulation stops boards sitting flat, and sharp objects can puncture the membrane.

If pipes or cables cross the floor, they should be dealt with below the screed, usually within the insulation layer, rather than left sticking up into it. Anything that reduces the depth of the screed creates a weak spot.

Insulation that sits flat and tight

Floor insulation boards must sit flat on the base without rocking, and be pushed tight together. Check for:

• boards that move or spring when you walk on them
• gaps between boards, or between boards and walls

A perimeter edging strip

An edging strip is a band of compressible foam fixed around the edge of the floor. It lets the screed expand and contract slightly without pushing against the walls.

It needs to go around everything the screed will touch: walls, columns, steps, door frames and any pipes coming up through the floor. It should stand higher than the finished screed level.

A membrane that makes the floor watertight

Over the insulation goes a membrane, usually a polythene sheet. Its job is to stop the liquid screed getting between or under the insulation boards. If screed gets underneath, boards can lift.

For it to work:

• overlap the sheets generously and tape every joint
• turn the membrane up at the edges or tape it to the edging strip, so the floor forms a continuous tray
• seal around anything that passes through it
• check for tears after other trades have walked on it, and tape any you find

Underfloor heating pipes fixed, filled and tested

If the floor has underfloor heating, the pipes go down before the pour. This is the heating installer's work, but it is worth checking that:

• the pipes are fixed down securely across the whole floor, because loose pipes can lift when the screed flows around them
• the system has been filled and pressure-tested, so any leak is found while the pipes can still be reached
• you know whether the installer wants the system left under pressure during the pour

Levels and depth

Agree the finished floor level before the day of the pour. Think about door thresholds, stairs, the floors of adjoining rooms and the thickness of the floor finish you have chosen.

Then check that the depth available suits the screed across the whole floor, not only at one corner. Bases are rarely perfectly level, so the screed will be thinner over the high points. The minimum depth, including the cover over heating pipes, should follow the screed manufacturer's guidance.

Edges, doorways and joints

Where the screed needs to stop, for example at a doorway into a room that is not being screeded, a temporary barrier has to be fixed and sealed so the liquid cannot run through.

Ask too whether movement joints are needed. A movement joint is a planned break that lets sections of screed move independently. They are often considered at doorways and between heating zones that are controlled separately.

Access for the pump

Liquid screed is pumped into the building through a hose, so think about how the delivery and the pump will reach the site. A clear place to park close to the building and an unobstructed route for the hose both help.

Whether the site is in the middle of Bridgwater or Taunton or out in the countryside, mention anything awkward when you ask for a quotation, such as a narrow lane, a shared drive or restricted parking.

On the day, and straight after

• Clear the floor of tools, materials and trestles.
• Keep other trades out of the area.
• Afterwards, keep off the floor until your installer says it can be walked on, and follow their advice on ventilation.

Drying time depends on the depth of the screed and the conditions on site. Floor finishes should only go down once a moisture test confirms the screed is dry.

Ready to book

We supply and install liquid screed for extensions, renovations, new builds and commercial floors across Somerset, Dorset and the surrounding areas. Message us with your floor area and location for a free quotation.