Loft joists

[Damo1176]

I currently have a loft part insulated well about 1/3 of it insulated with 100mm loft blanket. I want to raise this to 200mm loft blanket but my joists are only 75mm high. Now I want to board most if not all of the loft, I have no tanks in there whatsoever. So as not to lose the properties of 200mm insulation I understand I have to raise the joists.

Can someone tell me the best way of doing this? Can I just get some 4x2 and fix that to the joists the natural way they run or should I run them across therefore squeeze the 100 mm into the 75 mm joists and then run the other 100mm blanket across the lower joists and in between the raised ones before then boarding on top?

any advice on timber and best ways very much appreciated

 

[chappers]

I would do it the second way you described just get some sawn 4x 2 and skew nail it into the existing ceiling joists.

 

[Damo1176]

My concern is because my existing joists are only 3 x2 at the very most I am a bit nervy about putting 4x2 on the top because of the extra weight but I have no idea how else I can arrange it so I can have 200m of insulation. My only choice seems to be have 100mm under the boarded part whichI can reduce to half the loft and then for the rest lay the 100 between the joists and put the other 100mm across the top of the joists.

Any other ideas gratefully received.

Thanks

 

[Johnboy54]

Don't forget that 3 x 2 trusses aren't designed for jumping about on.
You're going to add the weight of insulation...
Lengths of 4 x 2...
Floorboarding...
Whatever you put up there...
And then you!
The ends of the 3 x 2 most likely won't get covered and strengthened by the 4 x 2 going on top, which means you're still adding all the weight to the 3 x 2.
I'd confine the boarded area to a minimum, and have it over any walls below.
I'd be inclined to screw the 4 x 2 in place. Hammering may not be to the liking of the plaster below.