Why engineered wood is the usual choice over heating
Engineered boards are built in layers, with a wood surface on a layered core. The Solid Wood Flooring Company recommends them for heated floors and says never to install solid wood flooring over underfloor heating. Other makers publish their own lists of suitable products, so the product data sheet is the document that settles whether a given board is approved.
The guide to engineered and solid wood flooring compares the two products, and the subfloor preparation guide explains how a screed is tested before boards go down.
The same supplier also says never to buy cheap engineered flooring, and recommends boards dried to at least 8% moisture content. A board that suits a heated floor is a specified product, not a style choice.
The 27°C surface limit
What the sources say
Bona's guidelines, written around BS 8201:2011, state that the surface must not exceed 27°C while underfloor heating is in use. The Solid Wood Flooring Company gives the same ceiling and says the screed surface must never exceed it.
Why a thermostat does not enforce it
The Solid Wood Flooring Company says surface temperature is controlled with flow control valves, not room thermostats, and recommends sensors in the screed that switch the system off at 27°C. A room thermostat reads air temperature, so it can read comfortable while one patch of floor runs hot.
Rugs and carpet
A covering on a heated floor holds the heat in. The same supplier warns that carpet on a wood floor can raise the temperature between floor and carpet by about 15°C. Tell the heating installer which rooms will have rugs before the flow temperature is set.
Screed moisture: the sources disagree
Moisture is the part of the job where published figures conflict, and the conflict is the reason to ask for a measured reading.
| Source | Limit given | Measure |
|---|---|---|
| Bona (BS 8201:2011 guidelines) | 75% RH, or 65% RH for floors bonded directly to the screed | Relative humidity |
| The Solid Wood Flooring Company | Concrete screed below 1.8% before heating starts; a 75mm screed takes at least 75 days to get there | Moisture content |
The two figures use different units, so they cannot be compared directly. Ronacrete, a screed maker, notes that many wood flooring suppliers dispute that the 75% RH figure applies to anything other than floating floors. Neither page lists a limit for every screed type.
Ask the fitter to measure the screed, name the method, and show the reading against the limit in the board maker's installation guide. The same supplier adds that sand and cement screeds need a damp-proof membrane and anhydrite screeds must not be sealed with one, because moisture harms their structure.
The warm-up routine
Bona's default schedule
Bona says to commission the heating to the heating manufacturer's guidelines where they exist. Where they do not, it gives a default: raise the flow temperature by 10°C a day, from 20°C on day 1 to 50°C on day 4 (or the system maximum if lower), and hold it for at least 7 days. Cool it down by 10°C a day and then turn it to a low setting.
The longer alternative
The Solid Wood Flooring Company asks for a 21-day run. The company starts the pipe water at 20°C, raises it by no more than 5°C every 24 hours up to 45°C, holds the maximum for about 8 days, then reduces it over about 8 days. The company also says never to install wood before commissioning and to ask the installer for documented temperatures.
After the boards go down
The same supplier advises waiting at least 48 hours after fitting before turning the system on, up to 14 days for natural oil finishes, then raising the temperature by 1°C to 2°C a day. Bona gives 18°C as the surface ceiling while the timber is being installed.
The two schedules side by side
| Bona default (BS 8201 based) | Solid Wood Flooring Company | |
|---|---|---|
| Start | 20°C on day 1 | 20°C on day 1 |
| Step | Up 10°C a day | Up by no more than 5°C every 24 hours |
| Peak | 50°C (or the system maximum if lower) by day 4 | 45°C |
| Hold | At least 7 days | About 8 days |
| Cool down | Down 10°C a day, then a low setting | Reverse the ramp over about 8 days |
| Total | About 15 days | 21 days |
The routines differ by about six days and by 5°C at the peak, and neither claims to replace the manufacturer's sheet for your heating system. Use the heating installer's commissioning sheet if there is one, and ask for the logged temperatures, as the supplier advises.
What to do if the schedules do not suit your system
Bona says to follow the heating manufacturer's guidelines where they exist and to use its schedule only where they do not. If your installer gives you a different routine, ask which standard it follows and keep a copy with the quote.
What the heating installer should hand over
The Solid Wood Flooring Company says never to install wood before commissioning and to ask the installer for documented temperatures. The company also recommends sensors in the screed that switch the system off at 27°C. Ask for the commissioning sheet and the temperature log, and keep a copy with your quote. You are entitled to see what the heating did before your floor went down.
Fixing method and subfloor
Glued, floating or nailed
The supplier's page glues boards to concrete and anhydrite screeds with an MS polymer adhesive. For floating floors it prefers gluing and recommends a heat-flow underlay with a quality wood adhesive. If boards are secret-nailed or screwed, there must be no air gap between the boards and the heating and boards must never touch a hot water pipe.
Timber subfloors
For heating on a timber subfloor, the supplier sets a timber moisture limit of 10% and joists at no more than 350mm centres. The supplier also sets evenness at a maximum deviation of 3mm under a 3m straight edge.
Room humidity and expansion gaps
The supplier gives room humidity targets of 40% to 65% for acclimatisation and 35% to 60% in use, and a perimeter expansion gap of 8mm, often 13mm to 15mm. The supplier's page flags some figures that vary from section to section, so treat it as one maker's guidance, not a standard.
What to put in the quote
- The exact board, and the maker's written approval for use over underfloor heating.
- Who measures the screed, with which method, and the reading that allows fitting to start.
- The fixing method the maker allows over heating: bonded or floating.
- Who runs the warm-up, for how many days, and what temperatures are logged.
- What happens to the schedule if the screed has not dried.
A quote with those lines is easier to compare than a bare price per square metre. The flooring fitting costs guide shows how to compare quotes on like-for-like terms.
Your part in the routine
You control how the rooms are used while the floor settles. Keep rugs off a newly laid floor until the heating is running normally, and ask the fitter when you may turn the system on, because the supplier's own advice is to wait at least 48 hours.
Finding a fitter who has done this
63 Welsh businesses list wood and parquet floor fitting. Ask each one for a recent job over underfloor heating and for the installation guide they followed. The directory does not verify that a fitter has done heated-floor work, so ask for photos and a past customer's phone number. The guide to hiring a flooring fitter in Wales gives the checks to run on the answer.
What this page does not cover
The page reports two published guidelines and one disputed point from a screed maker. The page does not reproduce BS 8201 or BS EN 1264, which are paid standards. The page does not cover electric mat systems, dry-screed systems or any named board. Treat the board maker's installation guide and the heating system's commissioning sheet as the authority.