Loft joists (in-situ concrete home)

I am considering boarding my loft space. Its primary purpose will be storage but I would like to future-proof it in case I decide to add a dormer.



I initially thought I could simply add a ledger board to the party wall and run joists across to the wall plate. However, after inspecting the loft I discovered this is not the case. The house is a 1950s in-situ concrete semi-detached with a hipped roof. The wall plate appears to be lower than where the joists and rafters meet. I had not noticed this previously but it is apparent from the landing and a bedroom as shown in the photograph.



I am seeking advice on how to proceed. Is future-proofing worthwhile? Would I need to drop the ceilings so the joists are level with the wall plate? Alternatively, could I build a subfloor incorporating the existing joists?

Here are a few of the attic also showing the attic overall, the wall plate lower than the joists and the joist attaching to the rafter.




Any help most appreciated, tia.

Your roof looks fairly typical, typically the principle for converting such a loft would be to fit a steel beam just above your existing ceiling joists beneath each purlin, then build a structural timber stud wall off the new beams to support the purlins, then any ties or struts can be removed, then the new floor joists can span between each steel beam to create the new floor. So your original wall plates will not have anything new bearing on them. If you wanted a dormer then you would typically also fit a steel ridge beam which supports both the the back of the dormer flat roof and the rafters at the ridge. So future proofing for a loft conversion is perfectly doable but extremely expensive should you decide not to proceed with the loft conversion. All assuming you actually have enough height to convert the loft space, BTW you can do a hip to gable extension under permitted development usually.

The ridge looks way too low for a sensible loft conversion.