Case study
Loft Insulation Case Study — Raised Central Walkway With 300mm Insulation Either Side, Basingstoke
A raised central walkway had to be kept for storage and roof access, with no insulation on either side of it. The 35m² floor was insulated on both sides with 300mm of Knauf glass mineral wool, without compressing it under the boards.
What we found
- •A raised central walkway with open joists on both sides
- •The boarding provided access but had no effective insulation
- •A blockwork gable wall and clear roof structure in good condition
- •Long uninsulated runs alongside the walkway
The problem
The central walkway had to be kept for access to stored items and roof services, but there was no insulation on either side of it, leaving a large proportion of the ceiling uncovered.
The walkway itself was useful, yet most of the ceiling area remained exposed. This meant the loft still performed poorly despite having a practical access route.
Our assessment
The unboarded loft floor measured approximately 35m². The raised walkway could remain in place without compressing the new insulation. We recommended 300mm of Knauf glass mineral wool on both sides, with 100mm between the joists and 200mm cross-laid above.
The installation
The first layer was fitted between the joists from the walkway out towards each eave. Rolls were cut neatly around the walkway supports and blockwork junctions.
The 200mm top layer was installed across the joists on both sides, finishing flush with the raised board edges. The walkway remained clear and fully usable, while the eaves ventilation route was preserved.
The result
The loft retained its central access route and gained full-depth insulation across the surrounding floor, brought up to the edge of the boards without being compressed beneath them.
The installation helped to
- Retained a safe raised access route
- Prevented compression of the new insulation
- Reduced heat loss on both sides of the walkway
- Improved upstairs comfort
- Created a neat and practical finished loft
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