Underfloor Requirements Topflor is not suitable for wet rooms such as bathroom, toilette, sauna or wash rooms, as wood swells and changes shape. Wood makes up 80% to 85% of Topflor flooring. Wood works and moves. As a result, minimal irregularities can occur between adjacent panels. These are in the order of a maximum of 0.2 mm. Are the rooms in which you want to lay Topflor suitable? Type of Underfloor Pre-treatment of the underfloor Expansion Distances Masking Expansion Joints Next - Type of Underfloor