4.03.2021 Let me in 2! "The Observatory Porch."

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An external door, with roof over, could provide an air lock, porch-like entrance on the right.[SE corner] Without needing connecting doors between the buildings. Now that's something to seriously consider. It would look in keeping with the new building. As well as providing more roomy access than a central door.

Perhaps even helping to open up new possibilities in internal stair arrangements. Which might not otherwise work. Not even within the larger footprint becoming available. The second to last [new] post would need to be removed. To make room for the new door.

Here [Image right] I have mocked up a less pronounced doorway using scrap ply for a forward extension of the octagon's easterly wall. The SE octagon, support post, remains untouched. The red bars on the ground [at bottom right] represent a new foundation block. This will be moved over from where the second [new] post once stood. 

The lower post section of this same post moves too. Otherwise it will block the doorway. The new post will support the right hand side of the doorway. As well as the extended master joist and the extended eastern wall. The upper part of the same post must remain in the upper observatory wall to continue the smooth, cylindrical form. In the image [above right] I have painted out this post in its original position.

The red cross [Right] shows the octagon's, SE, cladding panel. Which will be completely removed. Or even become the new door's outer panel. I can fit an 80cm wide door into the newly framed gap. This new "porch" entry arrangement will need a small plywood roof. Which will be covered in heavy duty rubber and provided with flashing to shed run-off from above. 

The next image [Left above] shows the latest physical mock-up. With a full length 2x8 added onto the original, main joist on the front of the octagon. A 3m high 2x4 upright post has been fixed to the far right of the joist to represent a doubled post. Though I haven't moved the foundation block over yet.

[Image Right] Here I have crudely painted in a door and "porch" roof. If the door was hinged on the new post [on the right] it would open back against the extended rear wall. Thereby avoiding any potential obstruction on the ground floor of the observatory. 

This greater freedom will maximise the hope of resiting the access stairs to the outer wall of the larger, observatory dome. Or provide much more space for a more gently sloping set of stairs. Or both!

Yet again it comes back to clearing, while still supporting, the octagon's vital, floor and main joists. These are structural and their role must be fully respected. Though framing around an open stairwell can be achieved. Without loss of strength and stiffness. By using larger timbers and careful design. Much like an attic trapdoor opening in the ceiling of a domestic building.

My apologies for a lengthy and rather confusing text. I kept changing the images and mock-ups as I made improvements. The double doors on the left of the new door, will go. This structure will be lost inside the larger footprint. Now I just need to properly support the upper half of the missing post in the observatory wall.

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