Each entry is quoted from its source and linked to it. The full set is in the standards reference.
Functional heating of a heated screed
IMI's commissioning instructions start functional heating of a heated screed no earlier than 21 days after laying for cement screed and 7 days for anhydrite, at 20 to 25 °C flow temperature for 3 days and then at the maximum design temperature for 4 days, in keeping with EN 1264-4, and state that functional heating does not ensure the screed is dry enough to be covered; that readiness is checked by the floor layer.
| earliest start, cement screed | 21 days |
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| earliest start, anhydrite screed | 7 days |
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| first stage flow temperature | 20-25 °C |
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| first stage duration | 3 days |
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| second stage at maximum design temperature | 4 days |
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“Carry out functional heating of heating screed conforming to standards in keeping with EN 1264-4. Earliest start for functional heating: – Cement screed: 21 days after laying – Anhydrite screed 7 days after laying Begin 20 °C - 25 °C flow temperature and maintain for 3 days. Then set maximum design temperature and maintain for 4 days. … Functional heating does not ensure that the screed has reached moisture content for readiness for covering. The readiness for covering the floor will be checked by the floor layer.”
Source: IMI Hydronic Engineering — Commissioning instructions for underfloor heating (9340-00.831-480, Index 00, 04.2021)Commissioning the heating before the floor goes down
Before any subfloor preparation or floorcovering is laid, the underfloor heating must be run through a full drying and commissioning cycle of heating up and cooling down, typically lasting about 21 days.
| typical duration of the heat-up / cool-down commissioning cycle | 21 days |
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“In all instances, UFH systems must be run through a full drying / commissioning cycle of heating up and cooling down before any subfloor preparation or installation of decorative floor coverings are installed. This period of commissioning is usually around 21 days.”
Source: CFA Guidance Document — Beyond Installation: Guidance on Underfloor Heating (Contract Flooring Association)The hygrometer method for subfloor moisture
In UK practice a hygrometer is sealed to the subfloor inside an insulated box with butyl tape and left until the air under the box reaches equilibrium; at least 4 hours before the first reading on a 50 mm screed with the DPM under the screed, and 72 hours where the DPM lies below the base slab.
| minimum time before first reading, 50 mm screed with DPM between base and screed | 4 hours |
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| minimum time before first reading, DPM below the base slab | 72 hours |
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“For 50mm thick screeds, where the damp proof membrane is placed between the base and the screed, a period of at least 4 hours should be allowed before the first reading is taken. For thicker constructions i.e. where the damp proof membrane is placed below the base slab, a period of 72 hours should be allowed to elapse before the first reading.”
Source: Digital Hygrometer - Technical Data Sheet, F. Ball and Co. LtdBS 8203 — relative humidity limit for a subfloor
UK practice following BS 8203 treats a subfloor as dry enough for resilient floor coverings when hygrometer readings do not exceed 75% relative humidity (65% RH for solid timber coverings), measured with a hygrometer sealed to the surface so that it reaches equilibrium with the base.
| RH limit, resilient floor coverings | 75 % RH |
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| RH limit, solid timber floor coverings | 65 % RH |
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“The base can be considered dry enough to install most floorcoverings if a series of tests produce readings not exceeding 75% R.H. (65% R.H. for solid timber floorcoverings).”
Source: F. Ball and Co. Ltd - Digital Hygrometer, Technical Data SheetHow long a screed takes to dry
BS 8204-1 gives a drying allowance of one day per millimetre of thickness for the first 50 mm of a levelling screed, with longer per-millimetre times above that thickness, so a 50 mm screed drying in good conditions takes roughly two months.
| drying allowance, first 50 mm | 1 day per mm |
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| thickness covered by the 1 day/mm rule | 50 mm |
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| resulting drying time for a 50 mm screed, good conditions | about 2 months |
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“with levelling screeds, one day should be allowed for each millimetre of thickness for the first 50 mm, followed by an increasing time for each millimetre above this thickness. It is therefore reasonable to expect a levelling screed 50 mm thick, drying under good conditions, to be sufficiently dry in about 2 months.”
Source: Drying of Screeds - RonacreteAcclimatisation before fitting
The Contract Flooring Association's guide states that the room should be at its in-service temperature 48 hours before installation so that the flooring can be kept in the room and reach room temperature before it is laid.
| conditioning before installation | 48 h |
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“They also advise that this temperature should be attained 48 hours prior to the installation, so that floorings can be kept in the room and brought to room temperature (acclimatised) before installation.”
Source: CFA Guide to Contract Flooring - Contract Flooring AssociationRoom conditions at the time of fitting
The MMFA, the European association for multilayer modular floor coverings, requires the flooring to acclimatise for at least 48 hours in the same conditions as the installation area, stored flat and cross-stacked in unopened boxes at roughly 15-25 degrees Celsius and 35 to 65 per cent relative humidity.
| acclimatisation before installation | at least 48 h |
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| storage and acclimatisation temperature | 15-25 °C |
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| storage and acclimatisation relative humidity | 35-65 % |
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“Leave the floor covering to acclimatise in the same environmental conditions as the installation area for a period of at least 48 hours prior to installation. Always store the boards flat and cross-stacked, in their original unopened boxes and at approx. 15-25 °C and between 35 % and maximum 65 % relative humidity.”
Source: Prior to installation — MMFA (Multilayer Modular Flooring Association)Floor surface temperature: what most manufacturers state
The UK underfloor heating trade association says most floor covering manufacturers state a maximum floor surface temperature of 27 °C, which is more than adequate in the majority of situations, and that some manufacturers allow higher temperatures without compromising warranties.
| maximum floor surface temperature stated by most manufacturers | 27 °C |
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“Most manufacturers state 27°C, which is more than adequate in the majority of situations. In some circumstances, manufacturers will allow higher temperatures without compromising warranties.”
Source: BEAMA Underfloor Heating — Choosing your floor covering to maximise your underfloor heating efficiency (April 2020)Vinyl over underfloor heating: 26 °C
BEAMA advises that most vinyls should not be heated above 26 °C, so the floor temperature should be restricted, and warns that in rooms with high heat losses such as conservatories a restricted floor temperature may not heat the room sufficiently.
| maximum temperature for most vinyls | 26 °C |
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“However, as most vinyls should not be heated to above 26°C, the floor temperature should be restricted. Care should be taken in the design of systems in rooms with high heat losses, such as conservatories, as it may not be possible to sufficiently heat the room with a restricted floor temperature limit.”
Source: BEAMA Underfloor Heating — Choosing your floor covering to maximise your underfloor heating efficiency (April 2020)Parquet over underfloor heating: glued down, with a floor sensor
BEAMA describes parquet as suitable for underfloor heating, with the blocks continuously glued onto the screed or timber deck for good heat transfer and a floor temperature sensor always fitted.
“Parquet – Also suitable for use with underfloor heating, these floor blocks should be continuously glued onto the screed or timber deck for good heat transfer. A floor temperature sensor should always be fitted.”
Source: BEAMA Underfloor Heating — Choosing your floor covering to maximise your underfloor heating efficiency (April 2020)
