Can you board over loft insulation?
Yes, if the boards are raised on loft legs so the insulation underneath keeps its full depth. Boards screwed straight onto the joists squash the insulation to the joist depth, usually 100 mm, which can cut its performance by more than half.
What height should loft boarding be?
High enough to clear the insulation with a small air gap above it. For 270 to 300 mm of insulation on 100 mm joists, that means legs that lift the boards about 175 to 200 mm above the joists.
How much of the loft should be boarded?
Only what you need. Most people board an area around the hatch and a walkway to the tank. Every boarded square metre costs money and makes later checks harder.
How much weight can a boarded loft hold?
Boxes, cases and seasonal items are fine in most lofts. Trussed roofs, common in houses built since the 1960s, are designed for light loads, so heavy items need the structure checking first.
Related services
Sources: Energy Saving Trust: roof and loft insulation; Which?: loft insulation costs and savings; LABC: building regulation requirements for loft insulation; GOV.UK: extending the ECO4 end date, government response; GOV.UK: VAT on energy-saving materials (notice 708/6); Property Care Association: spray foam guidance.
