Loft boarding an insulation

[dyiorbust]

Hi,

I'm planning to board a section of my loft to create storage space, and to add rockwool insulation over the remaining space.

Currently the loft has no flooring, just the exposed joists (with rockwool between them).
Joists are 4x2 inches.

Having read various threads on the topic, it seems that one approach is to raise the existing joists by laying timber across in order to create space for extra insulation below the flooring.
Rightly or wrongly, I'm somewhat wary of getting into such structural work myself.

So, my plan at the moment:
1. Lay chipboard on top of the joists.
2. Cover the chipboard with 100mm Celotex (or similar insulation).
3. Cover the Celotex layer with thin hardboard (saw cheap 3mm sheets) to protect it and act as actual floor.

What do you guys think?

 

[PrenticeBoyofDerry]

Why do you think laying timbers to raise floor level, to allow for insulation, is any more structural than what you intend to do?

 

[dyiorbust]

I never did either, but I'm thinking (perhaps incorrectly) that laying timber across has more potential for problems than just laying loft flooring chipboard on top of the joists.
Essentially I'm looking for the simpler and more fail safe option, and welcome any advice on which that would be.

 

[PrenticeBoyofDerry]

Laying the raised timbers perpendicular to existing joist, is simple enough.
The main issue, is covering electric cable with thermal insulation as it effects the current carrying capacity of them, lighting circuits on 5A or 6A generally fine but power circuits can be an issue.

 

[dyiorbust]

Thanks.
Yes I'm aware of the issue with electric cables, especially that there is a 'fat' one up there for an electric shower. It is not located where I plan to lay flooring and I plan to re-lay it in a tray or trunking above the new insulation layer.

What would be the pros and cons (if any) of raised timbers across joists v. what I had in mind?

 

[PrenticeBoyofDerry]

raising the floor will allow for greater depth of insulation and likely to be cheaper material wise and you can lay timbers at distances suitable for your loft boards.
PS. installing cable within trunking, also reduces current carrying capacity.