Technical Information

Some General Guidance for Fitting

Solid Boards

Boards up to 150mm wide can be secretly fixed down to timber subfloor, either plywood or timber joists Boards over 150mm wide need to be face fixed down, 2 fixings either side of the board will be required at regular intervals down the length of the board. Fixings should be either nails or screws with pellets. We would only recommend boards 140mm and under to be glued down and only with glue recommended by Lawsons

Engineered Boards

These can be either glued or fixed and this applies to wider boards too. Also can be used over underfloor heating but guidelines still need to be followed

The maximum temperature at the point of contact (where the heating meets the underside of the floor) is 27 oC. In order to ensure that this is adhered to, we recommend the use of an underfloor heating system that controls this temperature by way of floor sensors (a probe).

The radiant heating system must not exceed 8 watts/sq.ft; heating capacity and the running water temperature should range between 38-49 oC at the most.

To preserve the integrity of the flooring the room temperature must not vary more than 9 oC between seasons and the humidity must be maintained between 45 and 60% relative humidity throughout the year. A humidifier should be used to maintain relative humidity if necessary.

During the heating period small hairline cracks may appear. These hairline cracks are generally evenly spread and are not cause for concern. They may also appear under rugs and furniture.

UFH Installation Guidlines

Before installing the Flooring radiant heat slabs must be activated to normal living temperatures for a minimum of 21 days. This will ensure that the slab is dry. During this period the temperature should be gradually increased until the maximum recommended temperature is reached. The maximum temperature should be maintained for at least a week.

Before installation reduce the temperature gradually by 5 oC per day. At the time of installation the subfloor temperature should be between 16– 18 oC.

The installation can now be carried out.

After installation the temperature of 16–18 oC should be maintained 3 – 4 days before it is increased gradually over a further 3 – 4 days to the recommended subfloor surface temperature of 24– 27 oC. Despite the season the recommended temperature of 24– 27 oC should be maintained for a further 3 – 4 days. Please keep a daily heating log during the installation period; this may be useful at a later date.

Underfloor heating should be treated as background heating and should not be used like conventional radiators where the temperature fluctuates often and can be turned up high quickly to heat up rooms.


 We recommend that all floors are acclimatised within their bundles for 2 to 3 days in the room to be installed to allow the temperature of the floor to equalize with its environment. Ensure that the building is enclosed and all wet trades finished. Verify the building is maintained at normal living conditions for temperature and humidity. Heating should be working for at least seven days preceding installation to promote proper acclimatisation. Packs should be stacked flat on the floor with battens in between layer to allow airflow around the stacks. If the delivery is for more than one room the order should be broken down into the individual room quantities and stored in the respective rooms. Do not store in damp unheated rooms. Extra acclimatisation may be required when using underfloor heating.  

All the above are only guidelines and it is the responsibility of the fitter be aware of them