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Screeds

Flowing screed.

Pumped flowing screed, also known as liquid screed, that self-levels for fast, flat floors over large areas, ideal for underfloor heating and tight programmes.

The work

Pumped, level and ready to programme

Flowing screed arrives as a liquid, is pumped into place and levels itself. There is no laying to rails, no tamping and no hand finishing across the bulk of the area. That produces a flat, dense floor far quicker than traditional sand and cement, with excellent coverage around underfloor heating pipes.

You will see the same product called liquid screed, flow screed, self-levelling screed or self-compacting screed depending on who is writing the specification. They describe the same method: a pumped, free-flowing screed that consolidates under its own weight.

Speed and cleanliness are the reasons it wins. A crew, a pump and a hose replace a barrow run and a floor full of labourers, which is what makes it viable in live and occupied buildings where a traditional screed simply cannot be programmed.

On site

Fast, flat and clean, even mid-programme.

A Trent crew levelling pumped flowing screed across an occupied-building floor plate.

The comparison

Liquid screed versus traditional sand and cement

This is the comparison most estimators are actually running, so here it is straight. For the wider choice between flowing, self-compacting and traditional systems, see screeds.

Speed

Liquid screed covers a large area in a single visit. Traditional screed is laid by hand in bays and takes considerably longer over the same floor plate.

Depth

Liquid screed can be laid thinner than traditional screed for the same performance, particularly over underfloor heating. Less depth means less weight on the structure and less material.

Underfloor heating

Liquid screed flows around and fully encases the pipes, so there are no voids against the pipe. Full contact means better heat transfer and a more responsive, more efficient system.

Flatness

Self-levelling gives a consistently flat surface across large areas without a skilled hand finish on every square metre.

Drying

The trade-off. Some liquid screeds dry no faster than traditional screed unless force-dried, and moisture content has to be right before coverings go down. Drying is a programme item to be designed in, not a benefit to be assumed.

Cost per square metre

Material is usually dearer, labour and programme usually cheaper. On a large floor plate liquid screed generally wins. On a small, constrained, chopped-up area it often does not.

Scoping

The decision you are actually making

Four questions set the price and the programme. Answer them at tender and the job runs clean.

  • Which binder? Liquid screeds are broadly either calcium sulphate based (also called anhydrite) or cementitious. Calcium sulphate screeds flow well and are widely used, but they are moisture-sensitive, form a surface laitance that usually has to be removed before adhered coverings, and are not suitable in permanently wet areas. Cementitious flowing screeds avoid both and cost more. The floor covering and the room use should decide this, not the price.
  • Bonded, unbonded or floating? Bonded goes directly onto a prepared base, unbonded sits on a membrane, floating sits on insulation, the normal arrangement over underfloor heating. Each has a different minimum depth and a different consequence if the base is out of tolerance.
  • What is the base doing? Screed follows the base. If the deck is out of level you either add depth, which adds weight and cost, or you regulate first. Confirm the deck survey before the screed is priced, not after.
  • What is going on top, and when? Moisture-sensitive coverings drive the drying programme, and the drying programme often drives the whole fit-out. If a vinyl or resin finish is following, the screed date and the covering date are linked and both need to be real.

Applications

Where liquid screed earns its place

Sector

Healthcare

Hospitals cannot stop. Pumped liquid screed goes down fast, in a clean, contained method, phased around clinical activity. We have delivered flowing screed in an operational hospital.

Read moreSector

Education estates

Term dates and exams set hard programme constraints. A pumped screed fits a holiday window in a way a traditional screed does not.

Read moreService

Upper decks & precast planks

Hollowcore decks need a screed that levels fast and reaches every part of the deck. Our placing booms deliver screed across upper floors without craning plant up.

Read more
Application

Large floor plates

Where coverage and flatness both matter over a big area, liquid screed delivers both quickly, and its cost advantage is clearest.

Application

Underfloor heating

Full pipe encasement, thinner cover, faster response, better efficiency. The commissioning and heat-up regime has to be planned in, following the manufacturer's heat-up profile.

Standards

Tolerances and standards

Screed surface regularity in the UK is normally specified to BS 8204, which sets three classes measured as the maximum deviation under a 2m straightedge:

Screed materials themselves are classified by binder type under BS EN 13813, which is what the manufacturer's declaration of performance refers to. We survey the finished screed against the class specified and issue the results.

Completed flowing screed floor installed by Trent at the John Radcliffe Hospital

Capability

Plant and crews, self-delivered

Our own operatives, our own pumps, our own placing booms, start to finish. Nothing about the screed works is subcontracted out.

Placing is the part that catches people out. A liquid screed is only as good as the pour that delivers it, and on constrained sites getting the material to the deck is the whole job. We run our own concrete line pumps and track-mounted placing booms, rare kit in this country. That reach is why we can screed upper decks, restricted spaces and buildings that are still in use, on projects other subcontractors decline.

Because the placing plant is ours, the method is planned as part of the works rather than bolted on. Pump positions, hose runs, boom set-up and wash-out are agreed before we mobilise.

Programme

Output, programme and constraints

Pumped screed covers ground quickly. The constraint is rarely the screed itself, it is access, delivery, pump set-ups and how much of the deck is genuinely ready. We programme from the ready date backwards.

  • Live and occupied buildings. The reason most clients call us rather than a general screeder. Phasing is agreed around the building's use, not around our convenience.
  • Method designed up front. Access windows, out-of-hours working, delivery routes, lift and door restrictions, noise limits and dust control all go into the method statement before we arrive.
  • Restricted access handled with plant. Where a pump cannot reach, the boom can. Where neither can, we will tell you at tender rather than find out on the day.
  • Honesty about readiness. If the deck preparation, insulation, UFH installation or edge detailing will not be complete when the programme says, we say so before the pump is booked. That conversation is cheaper early.

Proof

Evidence and documentation

  • Surface regularity survey against the specified BS 8204 class
  • Delivery tickets and batch records for the screed supplied
  • Pour records covering area, depth, date and conditions
  • Manufacturer's declaration of performance for the system installed
  • Moisture readings prior to floor coverings where we are asked to take them
  • RAMS issued and agreed before mobilisation
  • Sign-off pack at handover

We are Constructionline Gold registered, Avetta and SSIP accredited, and a member of the Nuclear Industry Association.

FAQs

Common questions

Is flowing screed the same as liquid screed?
Yes. Flowing screed, liquid screed, flow screed and self-levelling screed all describe a pumped screed that consolidates under its own weight. Specifications use the terms interchangeably.
Is flowing screed suitable for underfloor heating?
Yes, and it is the best method for it. It flows around and fully encases the pipes for complete contact, better heat transfer and a more efficient system, and it can be laid at less depth over the pipes than a traditional screed.
How disruptive is it to an occupied building?
Low. It is pumped, fast and contained, so it suits live and occupied environments with careful phasing. That is the main reason it is used in hospitals and schools.
How long before we can walk on it, and before floor coverings go down?
Foot traffic comes fairly quickly. Floor coverings depend on the screed drying to the moisture content the covering manufacturer requires, which is a programme item that has to be planned rather than assumed.
Calcium sulphate or cementitious, which should I specify?
Let the room and the floor covering decide. Calcium sulphate is widely used and flows well, but it is moisture-sensitive and usually needs its laitance removing before adhered coverings. Cementitious avoids both issues and costs more. Send us the finishes schedule and we will advise.
Can it be laid on a precast plank deck?
Yes, and it is a strong fit. Our placing booms deliver screed across upper decks without craning plant up.

Got a flooring or screed project coming up?

Send us the drawings and the specification, and we'll tell you straight whether we can deliver it, and how.

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