Solid wood floors can be nailed into existing wooden subfloors such as floorboards or plywood, but not into chipboard as this is not strong enough to hold the nails.
We do not recommend floating a traditional oak floor, the main reason for this is because solid oak boards are very susceptible to movement caused by changing humidity levels as temperatures rise and fall. This makes it important to have a solid floor fixed to the sub-floor.
Secret nailing or screwing is a preferred method of fitting solid oak flooring, this process involves using a nail gun or power driver to drive the fixing through the tongue of each oak board into the sub-floor or joist.
The tongues are kept hidden by the groove of the next board, ensuring the fixings are hidden. This leaves a fixing free finish to the laid floor.
Engineered wood can be floated over the top of the underlay and should be either glued using PVA wood glue or clicked together at the joints.
Some standard underlays have a built in moisture barrier which prevents moisture from the concrete or screed sub floor attacking the engineered flooring installed on top, the common types come with a foil backing. However if you are unsure the underlay specification will have DPM labelled on the packaging or description.
Engineered boards can also be fixed to the subfloor in the same method as solid oak if this is your preferred method of installation.