I want to install a wooden loft ladder and install new “raised” floor joists in the loft space of a detached house. The existing roof is of a trussed construction at 400mm centres (32mm x 95mm ceiling joists support the first floor ceiling). Whilst I am not seeking to design a habitable room in the loft (because of cost & the fire regs compliance issues), I do want to do the job properly.
I have purchased some new joists (47mm x95mm C16) to attached to the existing trusses to elevate the loft floor which I propose to fit 2400 x 600 x18mm T&G flooring. I wanted to do this to maintain the 270mm loft insulation and to not apply any additional pressure onto the first flooring ceilings.
I am only proposing to lift and board the centre of the loft space (2.5M x 12M) which has a 3.4m headspace, so pretty useful for storage and perhaps a project room.
My question is whether it’s better (stronger) to attach the new joists to each of the existing joists in parallel, or at right angles to them forming a new subframe?. Either way I want to raise the floor by 95mm to accommodate the existing insulation with an air gap below the new T&G flooring to avoid any condensation?.
Any advice is gratefully received.