Loft insulation - over joists or cut-to-fit?

[Gary 41]

Hi,
New member with an odd query. I am having to do my own loft insulation in my apartment building on the top floor. (*I have permission from building owner).

The professionals won't do it because they cannot install a hatch in between the joists (too small), and the only access point is over a boiler (very awkward to fit into, but I can manage it).

The joists above are metal, and I'm wondering if it is essential to cut the earthwool to fit between them. Would it affect the heat retention to just lay it over the top? It would make the job much quicker to just roll it out without cutting, and as I won't be able to use it for storage I wondered if it made a difference if it was uneven.

Thanks. Really appreciate the info on here. Have found some really useful tips over the years.
-G

 

[footprints]

Nice to be able to see the joists if you ever need to go up there. Remember where possible lift cables up on top of the insulation easier if they insulation is fitted in strips.Out of interest how beefy are the metal joists? Will they take your weight?

 

[foxhole]

Cross lay, inline then across joists.

 

[Gary 41]

Ah yes, seeing where they are would be useful and possibly save me falling through... hadn't thought of that. )

The joists are pretty solid and some are welded together. A while back someone went up there without a problem (pest control), so it should be ok.


Thanks both.