Loft Insulation Case Study — Large Loft Brought Up to a 300mm Insulation Depth, Manchester

The problem

The house had a large roof space, but the loft floor had never been properly insulated. Exposed joists ran across the full area, with older timber framing that required accurate cutting around each roll.

Because the area was larger than a typical loft, the amount of unprotected ceiling surface was significant. The central hatch also needed to remain clear throughout the installation.

Our assessment

The loft floor measured approximately 54m². The structure was dry and suitable for a standard cold-roof insulation upgrade. We recommended a full 300mm system, consisting of 100mm Knauf glass mineral wool between the joists and 200mm laid across the top to reduce thermal bridging.

The installation

The loft was divided into sections so the team could work safely from the hatch towards the gable wall. The first layer was installed tightly between the joists, with smaller sections cut around trimmers and timber intersections.

The second layer was cross-laid across the entire floor. Particular attention was paid to the perimeter, the hatch opening and the areas beneath the lower roof slopes. The final depth was checked at several points before the loft was cleaned and inspected.

The result

The finished loft had a continuous 300mm insulation layer across the full 54m² floor. The perimeter, the hatch opening and the areas beneath the lower roof slopes were all covered, and the final depth was checked at several points.