Loft Flooring & Storage Calculator
Calculate boarding, raised platforms, and load capacity for converting loft space to storage above 270mm insulation.
Loft Storage Guide
Insulation vs Storage Conflict
Modern Building Regs require 270mm loft insulation. Standard joists: 100mm deep. Therefore: insulation rises 170mm above joists. Boarding directly onto joists: crushes insulation, reduces thermal performance ~50%. Cold bridges across joists, causes condensation, lost energy. Solutions: raised loft floor — battens or plastic loft legs raise board level above insulation. Loft legs (e.g. LoftZone, Storefloor): plastic legs screw into joists. Allow full 270mm insulation underneath. Board level. Cost
Load Capacity
Loft joists in a typical UK pre-1980 house: NOT designed as floor joists. Designed only to support the plasterboard ceiling and minor loads. Typical capacity: 25-50 kg/m². Light storage (boxes, suitcases): generally OK. Heavy items (furniture, books, exercise equipment): risk of ceiling cracking and joist deflection. Modern truss roofs (most post-1970): designed with even less floor capacity. Some are explicitly NOT to be loaded between trusses. Check: look up technical specs for your specific r
Boarding Materials
P5 moisture-resistant chipboard: standard loft boarding. T&G edges. Strong, easy to lay. Heavy. Typical 1220×320mm × 18mm. OSB3: oriented strand board. Slightly cheaper than P5, similar properties. Lightweight loft panels: thin polystyrene or aluminium-faced lightweight boards. Easier to install single-handed (lifting up the loft ladder). Lower load capacity. Insulated loft boards: polystyrene-backed plywood. Provide structural surface + additional insulation. Premium price (~£40 per m² vs £15 f
Practical Tips
Lighting: install before boarding. Battery-powered LED lights with PIR sensors are simplest. Hard-wired pendant in centre, switched at hatch, ideal. Pull cord — keep cord accessible. Ventilation: most lofts use roof vents (tiles or eaves). Don't block these with stored items or insulation. Damp/condensation: caused by warm air rising into cold loft. Boarded floor with hatch should be sealed against draughts. Insulate hatch. Loft ladder: aluminium concertina ladders £100-200. Useful for occasiona
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