Screed problems, diagnosed properly

Debonding diagnosis

Hollow-Sounding Screed

A dull, hollow note under a tapped tile or a dragged coin usually means the screed has lost its bond to the substrate somewhere below. Not every hollow patch needs lifting — but every one needs checking properly.

Surface friability

Dusting Screed Surface

If your screed sheds a fine powder every time it's swept or walked on, something has interfered with the surface cure — it isn't usually a sign the whole floor has failed.

Edge & perimeter curling

Screed Curling at Edges

A screed edge that has lifted slightly and curled upward, usually along a wall line or at a threshold, is almost always a sign that one part of the floor dried faster than the rest of it.

Bond-failure repair

Debonded Screed Repair

Once a hollow area has been confirmed as a genuine debond rather than a cosmetic sound difference, there are three realistic repair routes — and picking the right one depends on the size and location of the affected area.

Pre-tiling levels

Uneven Floor Levels

If a spirit level or a laser rocks or shows daylight across a room, the floor underneath your new tiles or LVT isn't flat enough — and covering it up won't fix the problem, it'll just show it later.

UFH cover depth

Screed Too Thin for UFH

If a liquid screed pour ends up thinner than the specified cover over the underfloor heating pipework, you're looking at a real risk of heat striping, cracking along the pipe run, or the pipe itself being exposed.

Deep-pour drying

Screed Too Deep — Drying

A screed poured deeper than the design depth — often to make up for an uneven substrate — doesn't just cost more material, it dries dramatically slower, and that has a direct knock-on effect on your programme.

RH & moisture testing

Failed Moisture Test

A relative humidity reading above the threshold for your chosen floor covering is a common, manageable outcome — it means the floor needs more time or more help drying, not that anything has gone wrong with the screed itself.

Surface preparation

Laitance Not Sanded

Every calcium-sulphate screed forms a weak, powdery laitance skin as it cures — leave it on the surface and any tile or LVT adhesive bonded to it is really only bonded to dust.

Tile cracking diagnosis

Tiles Cracking Over Screed

A cracked tile is rarely just a tile problem — in the majority of cases the crack is telling you something about movement, bonding or preparation in the screed underneath it.

Vinyl flooring defects

LVT Telegraphing

When every crack, ridge or debris speck in the screed shows up as a shadow through the LVT above it, the floor prep — not the vinyl — is almost always to blame.

Timber flooring defects

Engineered Wood Cupping

Boards with raised edges and a dished centre almost always point to a moisture imbalance between the screed and the timber, not a defective floor.

Moisture defects

Damp Patches in Screed

A patch that stays visibly darker or damp for longer than the rest of the floor is telling you something specific about what's underneath it.

Odour and moisture issues

Screed Smells Damp

A musty smell rising from a floor, especially once carpet, wood or vinyl is down, is almost always trapped moisture rather than a fault with the screed material itself.

UFH installation defects

UFH Pipe Floating

Liquid screed is dense enough to lift poorly clipped pipe during the pour, leaving reduced cover that shows up as a hot stripe or a crack line once the heating runs.

UFH installation detailing

Screed Over UFH Manifold

A manifold sits at a fixed height with cabling and pipework converging on it — get the screed level or the protection wrong here and it's the hardest spot on the job to put right afterwards.

Structural cracking

Screed Cracks Over Doorway

A crack that runs neatly across a doorway or narrow opening is one of the most predictable places for a screed to crack — and one of the easiest to prevent at design stage.

Anhydrite screed defects

Shrinkage Cracks (Anhydrite)

Anhydrite screeds crack far less than sand-and-cement, but they're not immune — a small amount of fine shrinkage cracking during drying is normal, and knowing what's normal matters.

Screed surface defects

Screed Soft Spots

An area that flexes, feels spongy underfoot or sounds different when tapped is telling you the screed hasn't cured or bonded properly in that spot, and it needs sorting before flooring goes down.

Level and clearance issues

Screed Height & Doors

Doors that used to clear the floor and now drag or won't close usually mean the finished screed level ended up higher, or lower, than the level everything else in the room was set to.

Flatness & tolerance

Screed Not Level for Large-Format Tiles

Big tiles forgive nothing. A 3mm dip that a mosaic would hide shows up as a trip hazard under a 1200mm porcelain slab.

Wrong screed for the room

Gypsum Screed in a Wet Room

Anhydrite screed is a great product in the wrong room. Wet rooms need a screed chemistry that tolerates standing water, and gypsum isn't it.

Depth & UFH protection

Screed Failed Cover Depth

Cover depth isn't a nice-to-have figure on a datasheet — it's what stops pipes fracturing and floors cracking under load.

Substrate preparation fault

Insulation Movement Under Screed

A liquid screed only performs as well as the floor it's poured onto. If the insulation moves during the pour, the screed above it inherits every gap.

Damp-proof membrane risk

DPM Failure Under Screed

A liquid screed is only as dry as the ground beneath it lets it be. When the damp-proof membrane fails, moisture rises straight through, no matter how well the pour went.

Seasonal pouring risk

Cold Weather Screed Pours

Cold doesn't stop a screed pour, but it changes the plan. Temperature management before, during and after the pour is what keeps a winter job on track.

Seasonal drying delay

Screed Drying in Winter

The '1mm per day' rule assumes decent ambient conditions. A cold, damp winter site can push drying times out by weeks, not days.

Accelerated drying

Dehumidifier Drying for Screed

A dehumidifier can genuinely rescue a tight programme — but only if it's brought in at the right stage of the screed's cure.

Programme & risk management

Screed Programme Delay

The screed pour sits in the middle of the programme — late by a week, and every trade behind it moves too. Here's how we help keep that from happening.

Site logistics & risk management

Screed Pours on Restricted-Access Sites

Liquid screed's biggest advantage — it can be pumped almost anywhere — is also what makes it the right answer on sites where a mixer lorry simply can't get near the door.

Access & pumping logistics

Long Hose Runs

The pump stays on the road. The screed travels through the house, up the stairwell or across the garden — often 100m or more from the mixer.

Substrate compatibility

Block & Beam

Block and beam behaves differently to a ground-bearing slab under a liquid screed pour — here's what we check before we say yes.

Substrate compatibility

Suspended Timber

Suspended timber floors take liquid screed well when the deflection is checked first and the pour is designed to float rather than fight the structure.

Renovation & extension detailing

Matching Floor Levels

Extensions and part-refurbishments live or die on whether the new floor meets the old one flush — we set that datum before the first bag of insulation goes down.

Preparation & demolition

Removing Old Screed

Sometimes the honest answer to a failed floor is that the old screed has to come out completely before anything new goes in.

Repair strategy

Patch vs Full Rescreed

The cheapest fix isn't always the right one — but the most thorough fix isn't always necessary either. Here's how we actually decide.

Flatness standards

Levelling Tolerances

"Level" isn't a single standard. SR1, SR2 and specific finish requirements each mean something different, and getting the wrong one specified causes real problems downstream.

Acoustic performance

Acoustic & Flanking Noise

A failed Part E sound test often isn't a screed problem at all — it's noise flanking around the edges through a gap the screed detail was supposed to close.

Perimeter detailing

Missing Edge Insulation

A perimeter isolation strip is a small detail with a big job — missing it causes cracking, cold bridging and, on UFH floors, real heat loss.

UFH handover

Commissioning UFH

Turning the heating on too soon, or too fast, is one of the few ways a well-poured screed can still fail — commissioning has its own strict sequence.