Thank you for your summary of structure of your loft, it is unlikely that your ceiling joist span 20?.
Notwithstanding, the assessment of load build-up is important and will often govern how much capacity remains for ?live? load i.e. your storage requirements. All lofts have a residual capacity and we will need to work with you to establish what you can store in the loft space.
In order to validate this solution we would request some further information:
? Photo of loft ? A plan showing all walls below the loft area
With this data we can provide a definitive answer to your question.
Regards,
Jeremy Wedge MIstrutE CEng On Behalf of Loft Conversion UK
