Screed Fault Diagnosis
Screed Not Drying Out
Slow drying is usually explained by site conditions, screed depth or ventilation rather than a fault with the screed material itself.
Screed drying behind programme?
Call Exeter Liquid Screeders on 07791 510849 for a site review and proper moisture testing to establish what's actually happening.
Or call our landline on 01392 237700
Drying times quoted for liquid screeds are based on standard laboratory conditions, and real sites rarely match those exactly. Depth of pour, ambient temperature, humidity, ventilation and whether the building is fully weathertight all affect how quickly moisture actually leaves the slab, sometimes significantly.
It's important to separate 'not drying as fast as hoped' from 'not drying at all', as the latter usually points to a specific blocking factor — standing water ingress, a failed or missing damp proof membrane, or genuinely poor ventilation trapping moisture near the surface.
Before assuming the screed itself is defective, a methodical review of site conditions and testing history typically identifies the reason drying is behind programme.
Screed Not Drying Out — the points that decide it
- Quoted drying times assume standard laboratory conditions, rarely matched on site
- Greater screed depth extends drying time roughly in line with depth, not linearly with time alone
- Poor ventilation and low temperatures are among the most common causes of slow drying
- Water ingress (roof, windows, rain during construction) can re-wet a drying screed
- RH testing to BS 8203 / BS 5325 methodology gives an objective reading, not visual guesswork
- A missing or damaged DPM allows ground moisture to continually feed the screed
- Force drying with dehumidification can accelerate drying where conditions allow
Checking the obvious site factors first
Before assuming a problem with the screed, check whether the building has been consistently ventilated and kept above a reasonable ambient temperature, since cold, still, humid air significantly slows moisture evaporation from the surface. Confirm the building is genuinely weathertight — an open roof light, unglazed window, or a leak during the drying period can continually reintroduce moisture.
It's also worth reviewing the screed depth that was actually laid against what was specified, as thicker-than-designed areas will take longer to reach a testable moisture level even under otherwise good conditions.
Testing properly rather than guessing
Surface impressions — a screed 'feeling dry' to the touch — are not a reliable guide to readiness for flooring. In-situ relative humidity testing, carried out and interpreted in line with recognised methodology, gives an objective measurement that can be tracked over successive visits to confirm a genuine drying trend.
Where results plateau rather than continuing to fall, that's a stronger signal of an ongoing moisture source (such as ground water via a damaged membrane) rather than simply needing more time.
In short
Slow drying is usually explained by site conditions, screed depth or ventilation rather than a fault with the screed material itself.
Screed drying behind programme?
Call Exeter Liquid Screeders on 07791 510849 for a site review and proper moisture testing to establish what's actually happening.
Or call our landline on 01392 237700
Screed Not Drying Out — your questions
Screed drying behind programme?
Call Exeter Liquid Screeders on 07791 510849 for a site review and proper moisture testing to establish what's actually happening.
Screed Not Drying — Diagnosis & Fix
Liquid screed dries at roughly 1mm per day for the first 40mm, then slower. A 50mm pour should be tile-ready in 5–6 weeks in still, dry conditions.
If it's not drying, one of three things is usually wrong: no air movement, no dehumidification, or water still tracking in from an unresolved leak.
First things to check
Are all the windows sealed and the doors closed?
Is there a dehumidifier running 24/7?
Is fresh water tracking in from a roof or plumbing leak?
Has the UFH been commissioned and run through the drying schedule?
Force-drying protocol
Seal the space — Close windows and doors. Warm air needs to stay in.
Dehumidifiers — Two industrial dehumidifiers per 50m². Empty tanks daily.
Fans — Two air movers keeping the surface breeze at 1 m/s.
UFH commissioning — Run the UFH through the drying-out schedule from the manufacturer.
Test — Hair-hygrometer test at day 10 — retest weekly.