Even the best flooring product will fail if the subfloor is not properly prepared. We explain moisture testing, screeding, and surface regularity for Hertfordshire commercial sites.
Subfloor preparation is the single most critical phase of any commercial flooring installation, yet it is frequently underestimated or rushed. In our experience across hundreds of Hertfordshire projects, inadequate preparation accounts for more flooring failures than any product defect.
Moisture is the primary enemy. Concrete subfloors must be tested for relative humidity using in-situ probes per ASTM F-2170 before any adhesive is applied. The maximum allowable reading depends on the adhesive and flooring type. For most pressure-sensitive adhesives used with carpet tiles, 75% RH is the ceiling. For water-based adhesives and some vinyl installations, the limit may be as low as 65%.
Surface regularity is measured using a 2-metre straightedge. Under BS 8204, the maximum permissible deviation is 3mm. In older Hertfordshire buildings, particularly Victorian and Edwardian commercial properties, we frequently encounter deviations of 10mm or more. These must be corrected with levelling compounds or latex screeds before installation proceeds.
We use a range of preparation techniques depending on the substrate condition. Diamond grinding removes surface laitance and old adhesives. Shot blasting creates a mechanical key for new screeds. Self-levelling compounds flow into low spots to create a flat surface. Each method is chosen based on a site-specific assessment.
Cutting corners on preparation always costs more in the long run. A floor installed on an uneven or damp subfloor may develop adhesive failure, bubbling, or delamination within months. Our quotations always include a realistic preparation allowance, and we photograph and document the subfloor condition before starting any work.
