Boarding Loft with Caberfloor P5 18mm Chipboard

[Damian30]

Hi,

I am just about to cross baton my loft with 4" x 2" timbers (to increase insulation) and then board with 18mm T&G moisture resistant 18mm chipboard.

I've just been reading the recommended installation instructions on the Caberfloor website ( http://www.norbord.com/documents/Caberboard_Brochure_2009.pdf) and it suggests that boards should be stagger laid perpendicular to the joists at 400mm centres.

Although I will need to cut the 2.4m lengths in half to fit them in the car, the width of the loft space I am boarding is only 2.4m in any event - would it be a problem if the joints were not staggered and I had a single supported join down the centre of the boards?

Also, to cover a 2.4m span at 400mm centres I would need 7 (4"x2" joists), where as using 22mm chipboard at 600mm centres I would need only 5 joists. I know the 22mm panels are about 4kg heavier than the 18mm panel but does anyone have a gut feel on whether the total weight would still be lighter than the 18mm option with the extra 2 joists? I am concerned about adding too much additional weight to the (new build) ceiling which is only constructed with existing 75mm joists.

Any advice gratefully appreciated.

Many thanks,

Damian

 

[lfnfan]

In general, they suggest stagger-laying to avoid having all the ends resting on the same joist. The Norbord technical helpline could probably give you a definitive answer for your particular situation.

no idea about the total weight side of things!