I am in the process of insulating & boarding the loft, after raising the floor height to get in 250mm of Rockwool insulation, and put in a new 1.5m x .075m loft hatch.
I was just considering the materials (and the cost) that would be best to use if I was to put some kind of ceiling on the underside of the roof rafters, along with jablite insulation between the rafters. It’s not a proper habitable room so plaster board is not necessary, and it will be 3-5 years before its used as a proper playroom as the little one in under 3 at the moment.
My dad has suggested using plywood, but this would not be cheap for a loft with a floor area of 3.5m x 11m, at £25 for each 4’ x 8’ x 18mm sheet, I suspect 5mm sheets would be in the £6.50 region if I can find them.
I was just looking at 4’ x 8’ x 3mm Hardboard which is only £5.28, the cheapest option so far. I wasn’t shore whether to put the smooth side facing up or down though, down would give a better finish to the loft ceiling and it wouldn’t require painting.