Warm flat roof unusual detail and cladding

[liftfan]

Hi,

I’m looking to build a 3m extension at some stage.

In the mean time I’ve removed the existing hanging tiles and I’ve come across this unusual construction as shown below.


The first floor joists are visible on the external wall. They rest on a 10inch steel column that spans the gap.

I’m about to clad the external wall but I’d like to allow for a 3m warm flat roof extension off the back like this in the future:

Any pointers on how far down I should take the cladding for now to allow for the extension in the future?

How would the unusual existing layout affect the design of a warm flat roof?

Thanks.

 

[liftfan]

Just to add, I was planning on the following warm roof construction from top down:

Epdm
Osb 18mm
PIR 200mm
Vapour Barrier
Osb 18mm
Firing (1:40 3m long) 75mm

Giving approx 315mm from the top of the roof joists.

So, I’m really asking where can the joists for the extension go?!

 

[noseall]

You need to leave a lead flashing trailing beneath the bottom cladding plank.

The flat roof material would likely finish say 2750mm above DPC when you consider 2400mm FFL to ceiling + 150mm flat roof joists + 125mm insulation + deck + furrings etc.

 

[noseall]

So, I’m really asking where can the joists for the extension go?!

Oh, right - I was typing mine when you posted yours.
Er..dunno really. Mid-span steel beam back to that central pier on the house? Wall to wall longways?