Floor insulation requirement as recommended by PART L 2002 of the UK building regulations

Thickness of floor insulation for solid ground floors to achieve U-value of 0.25 W/m2K. The larger the floor area the less is the insulation thickness.
Perimeter to Area Ratio P/A PS Thickness PU Thickness
Up to 0.25 50mm 30 mm
From 0.25 to 0.29 60mm 40 mm
From 0.29 to 0.345 70mm 45 mm
From 0.345 to 0.425 80mm 50 mm
From 0.425 to 0.55 90mm 60 mm
from 0.55 to 0.73 100mm 65 mm

For maximum energy saving, we recommend increase in insulation thickness between 20 to 50% when using underfloor heating.

Thickness of floor iInsulation for suspended beam and block floors to achieve U-value of 0.25 W/m2K. The larger the floor area the less is the insulation thickness.
Perimeter to Area Ratio P/A PS Thickness PU Thickness
Up to 0.27 50mm 30 mm
From 0.27 to 0.33 60mm 40 mm
From 0.33 to 0.44 70mm 45 mm
From 0.44 to 0.60 80mm 50 mm
From 0.60 to 0.90 90mm 60 mm
From 0.90 100mm 65 mm


The calculations are based on concrete blocks with a lamda value of 0.18 W/mK